[syzbot] [bluetooth?] KASAN: slab-use-after-free Read in force_devcd_write

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 48f506ad0b68 Merge tag 'soc-fixes-6.13-2' of git://git.ker..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13f19f30580000
kernel config: https://syzkaller.appspot.com/x/.config?x=c22efbd20f8da769
dashboard link: https://syzkaller.appspot.com/bug?extid=bc71245e56f06e3127b7
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=17df9fe8580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/f42f936a7d8d/disk-48f506ad.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/5f5d9512f350/vmlinux-48f506ad.xz
kernel image: https://storage.googleapis.com/syzbot-assets/08855819fbb0/bzImage-48f506ad.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+bc7124...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: slab-use-after-free in force_devcd_write+0x31f/0x350 drivers/bluetooth/hci_vhci.c:327
Read of size 8 at addr ffff88805dfd8800 by task syz.0.616/6633

CPU: 1 UID: 0 PID: 6633 Comm: syz.0.616 Not tainted 6.13.0-rc3-syzkaller-00289-g48f506ad0b68 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
print_address_description mm/kasan/report.c:378 [inline]
print_report+0xc3/0x620 mm/kasan/report.c:489
kasan_report+0xd9/0x110 mm/kasan/report.c:602
force_devcd_write+0x31f/0x350 drivers/bluetooth/hci_vhci.c:327
full_proxy_write+0xfb/0x1b0 fs/debugfs/file.c:356
vfs_write+0x24c/0x1150 fs/read_write.c:677
ksys_write+0x12b/0x250 fs/read_write.c:731
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f4c25785d29
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fffacf7c428 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f4c25975fa0 RCX: 00007f4c25785d29
RDX: 000000000000000e RSI: 0000000000000000 RDI: 0000000000000003
RBP: 00007f4c25801aa8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f4c25975fa0 R14: 00007f4c25975fa0 R15: 00000000000018c5
</TASK>

Allocated by task 5945:
kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
kasan_save_track+0x14/0x30 mm/kasan/common.c:68
poison_kmalloc_redzone mm/kasan/common.c:377 [inline]
__kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:394
kmalloc_noprof include/linux/slab.h:901 [inline]
kzalloc_noprof include/linux/slab.h:1037 [inline]
vhci_open+0x4c/0x430 drivers/bluetooth/hci_vhci.c:634
misc_open+0x35a/0x420 drivers/char/misc.c:165
chrdev_open+0x237/0x6a0 fs/char_dev.c:414
do_dentry_open+0xf59/0x1ea0 fs/open.c:945
vfs_open+0x82/0x3f0 fs/open.c:1075
do_open fs/namei.c:3828 [inline]
path_openat+0x1e6a/0x2d60 fs/namei.c:3987
do_filp_open+0x20c/0x470 fs/namei.c:4014
do_sys_openat2+0x17a/0x1e0 fs/open.c:1402
do_sys_open fs/open.c:1417 [inline]
__do_sys_openat fs/open.c:1433 [inline]
__se_sys_openat fs/open.c:1428 [inline]
__x64_sys_openat+0x175/0x210 fs/open.c:1428
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 5945:
kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
kasan_save_track+0x14/0x30 mm/kasan/common.c:68
kasan_save_free_info+0x3b/0x60 mm/kasan/generic.c:582
poison_slab_object mm/kasan/common.c:247 [inline]
__kasan_slab_free+0x51/0x70 mm/kasan/common.c:264
kasan_slab_free include/linux/kasan.h:233 [inline]
slab_free_hook mm/slub.c:2353 [inline]
slab_free mm/slub.c:4613 [inline]
kfree+0x14f/0x4b0 mm/slub.c:4761
vhci_release+0xbb/0xf0 drivers/bluetooth/hci_vhci.c:670
__fput+0x3f8/0xb60 fs/file_table.c:450
task_work_run+0x14e/0x250 kernel/task_work.c:239
exit_task_work include/linux/task_work.h:43 [inline]
do_exit+0xad8/0x2d70 kernel/exit.c:938
do_group_exit+0xd3/0x2a0 kernel/exit.c:1087
get_signal+0x2576/0x2610 kernel/signal.c:3017
arch_do_signal_or_restart+0x90/0x7e0 arch/x86/kernel/signal.c:337
exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
exit_to_user_mode_prepare include/linux/entry-common.h:329 [inline]
__syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
syscall_exit_to_user_mode+0x150/0x2a0 kernel/entry/common.c:218
do_syscall_64+0xda/0x250 arch/x86/entry/common.c:89
entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff88805dfd8800
which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 0 bytes inside of
freed 1024-byte region [ffff88805dfd8800, ffff88805dfd8c00)

The buggy address belongs to the physical page:
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x5dfd8
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000040 ffff88801ac41dc0 dead000000000100 dead000000000122
raw: 0000000000000000 0000000000100010 00000001f5000000 0000000000000000
head: 00fff00000000040 ffff88801ac41dc0 dead000000000100 dead000000000122
head: 0000000000000000 0000000000100010 00000001f5000000 0000000000000000
head: 00fff00000000003 ffffea000177f601 ffffffffffffffff 0000000000000000
head: 0000000000000008 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5606, tgid 5606 (dhcpcd), ts 41765829328, free_ts 41751365215
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x2d1/0x350 mm/page_alloc.c:1558
prep_new_page mm/page_alloc.c:1566 [inline]
get_page_from_freelist+0xfce/0x2f80 mm/page_alloc.c:3476
__alloc_pages_noprof+0x223/0x25b0 mm/page_alloc.c:4753
alloc_pages_mpol_noprof+0x2c9/0x610 mm/mempolicy.c:2269
alloc_slab_page mm/slub.c:2423 [inline]
allocate_slab mm/slub.c:2589 [inline]
new_slab+0x2c9/0x410 mm/slub.c:2642
___slab_alloc+0xce2/0x1650 mm/slub.c:3830
__slab_alloc.constprop.0+0x56/0xb0 mm/slub.c:3920
__slab_alloc_node mm/slub.c:3995 [inline]
slab_alloc_node mm/slub.c:4156 [inline]
__do_kmalloc_node mm/slub.c:4297 [inline]
__kmalloc_noprof+0x2de/0x4f0 mm/slub.c:4310
kmalloc_noprof include/linux/slab.h:905 [inline]
load_elf_phdrs+0x103/0x210 fs/binfmt_elf.c:532
load_elf_binary+0x14c6/0x4ed0 fs/binfmt_elf.c:961
search_binary_handler fs/exec.c:1748 [inline]
exec_binprm fs/exec.c:1790 [inline]
bprm_execve fs/exec.c:1842 [inline]
bprm_execve+0x703/0x19b0 fs/exec.c:1818
do_execveat_common.isra.0+0x4f1/0x630 fs/exec.c:1949
do_execve fs/exec.c:2023 [inline]
__do_sys_execve fs/exec.c:2099 [inline]
__se_sys_execve fs/exec.c:2094 [inline]
__x64_sys_execve+0x8c/0xb0 fs/exec.c:2094
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
page last free pid 5498 tgid 5498 stack trace:
reset_page_owner include/linux/page_owner.h:25 [inline]
free_pages_prepare mm/page_alloc.c:1127 [inline]
free_unref_page+0x661/0x1080 mm/page_alloc.c:2659
__put_partials+0x14c/0x170 mm/slub.c:3157
qlink_free mm/kasan/quarantine.c:163 [inline]
qlist_free_all+0x4e/0x120 mm/kasan/quarantine.c:179
kasan_quarantine_reduce+0x195/0x1e0 mm/kasan/quarantine.c:286
__kasan_slab_alloc+0x69/0x90 mm/kasan/common.c:329
kasan_slab_alloc include/linux/kasan.h:250 [inline]
slab_post_alloc_hook mm/slub.c:4119 [inline]
slab_alloc_node mm/slub.c:4168 [inline]
kmem_cache_alloc_node_noprof+0x1ca/0x3b0 mm/slub.c:4220
__alloc_skb+0x2b3/0x380 net/core/skbuff.c:668
alloc_skb include/linux/skbuff.h:1323 [inline]
netlink_alloc_large_skb+0x69/0x130 net/netlink/af_netlink.c:1196
netlink_sendmsg+0x689/0xd70 net/netlink/af_netlink.c:1866
sock_sendmsg_nosec net/socket.c:711 [inline]
__sock_sendmsg net/socket.c:726 [inline]
__sys_sendto+0x488/0x4f0 net/socket.c:2197
__do_sys_sendto net/socket.c:2204 [inline]
__se_sys_sendto net/socket.c:2200 [inline]
__x64_sys_sendto+0xe0/0x1c0 net/socket.c:2200
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
ffff88805dfd8700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88805dfd8780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88805dfd8800: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88805dfd8880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88805dfd8900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
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If the report is already addressed, let syzbot know by replying with:
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If you want syzbot to run the reproducer, reply with:
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If you want to undo deduplication, reply with:
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[Edward Adam Davis]

#syz test: https://github.com/ea1davis/linux bt/syz

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
KASAN: slab-use-after-free Read in force_devcd_write

==================================================================
BUG: KASAN: slab-use-after-free in force_devcd_write+0x32d/0x350 drivers/bluetooth/hci_vhci.c:336
Read of size 8 at addr ffff8880723fe000 by task syz.0.616/7968

CPU: 0 UID: 0 PID: 7968 Comm: syz.0.616 Not tainted 6.12.0-syzkaller-10299-g8e1aa2966d94 #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
print_address_description mm/kasan/report.c:378 [inline]
print_report+0xc3/0x620 mm/kasan/report.c:489
kasan_report+0xd9/0x110 mm/kasan/report.c:602

force_devcd_write+0x32d/0x350 drivers/bluetooth/hci_vhci.c:336

full_proxy_write+0xfb/0x1b0 fs/debugfs/file.c:356
vfs_write+0x24c/0x1150 fs/read_write.c:677
ksys_write+0x12b/0x250 fs/read_write.c:731
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

RIP: 0033:0x7f5b6e785d29

Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48

RSP: 002b:00007f5b6f56d038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f5b6e975fa0 RCX: 00007f5b6e785d29

RDX: 000000000000000e RSI: 0000000000000000 RDI: 0000000000000003

RBP: 00007f5b6e801aa8 R08: 0000000000000000 R09: 0000000000000000

R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000

R13: 0000000000000000 R14: 00007f5b6e975fa0 R15: 00007ffd5c295678
</TASK>

Allocated by task 6486:

kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
kasan_save_track+0x14/0x30 mm/kasan/common.c:68
poison_kmalloc_redzone mm/kasan/common.c:377 [inline]
__kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:394
kmalloc_noprof include/linux/slab.h:901 [inline]
kzalloc_noprof include/linux/slab.h:1037 [inline]

vhci_open+0x4c/0x430 drivers/bluetooth/hci_vhci.c:639

misc_open+0x35a/0x420 drivers/char/misc.c:165
chrdev_open+0x237/0x6a0 fs/char_dev.c:414
do_dentry_open+0xf59/0x1ea0 fs/open.c:945
vfs_open+0x82/0x3f0 fs/open.c:1075
do_open fs/namei.c:3828 [inline]
path_openat+0x1e6a/0x2d60 fs/namei.c:3987
do_filp_open+0x20c/0x470 fs/namei.c:4014
do_sys_openat2+0x17a/0x1e0 fs/open.c:1402
do_sys_open fs/open.c:1417 [inline]
__do_sys_openat fs/open.c:1433 [inline]
__se_sys_openat fs/open.c:1428 [inline]
__x64_sys_openat+0x175/0x210 fs/open.c:1428
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 6486:

kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
kasan_save_track+0x14/0x30 mm/kasan/common.c:68
kasan_save_free_info+0x3b/0x60 mm/kasan/generic.c:582
poison_slab_object mm/kasan/common.c:247 [inline]
__kasan_slab_free+0x51/0x70 mm/kasan/common.c:264
kasan_slab_free include/linux/kasan.h:233 [inline]

slab_free_hook mm/slub.c:2338 [inline]
slab_free mm/slub.c:4598 [inline]
kfree+0x14f/0x4b0 mm/slub.c:4746
vhci_release+0xbb/0xf0 drivers/bluetooth/hci_vhci.c:675

__fput+0x3f8/0xb60 fs/file_table.c:450
task_work_run+0x14e/0x250 kernel/task_work.c:239
exit_task_work include/linux/task_work.h:43 [inline]

do_exit+0xadd/0x2d70 kernel/exit.c:938
do_group_exit+0xd3/0x2a0 kernel/exit.c:1087
get_signal+0x2576/0x2610 kernel/signal.c:3016

arch_do_signal_or_restart+0x90/0x7e0 arch/x86/kernel/signal.c:337
exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
exit_to_user_mode_prepare include/linux/entry-common.h:329 [inline]
__syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
syscall_exit_to_user_mode+0x150/0x2a0 kernel/entry/common.c:218
do_syscall_64+0xda/0x250 arch/x86/entry/common.c:89
entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff8880723fe000

which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 0 bytes inside of

freed 1024-byte region [ffff8880723fe000, ffff8880723fe400)

The buggy address belongs to the physical page:

page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x723f8

head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)

raw: 00fff00000000040 ffff88801ac41dc0 ffffea0001e8f600 dead000000000002

raw: 0000000000000000 0000000000100010 00000001f5000000 0000000000000000

head: 00fff00000000040 ffff88801ac41dc0 ffffea0001e8f600 dead000000000002

head: 0000000000000000 0000000000100010 00000001f5000000 0000000000000000

head: 00fff00000000003 ffffea0001c8fe01 ffffffffffffffff 0000000000000000

head: 0000000000000008 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated

page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5899, tgid 5899 (syz-executor), ts 74750997698, free_ts 73623015670
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x2d1/0x350 mm/page_alloc.c:1556
prep_new_page mm/page_alloc.c:1564 [inline]
get_page_from_freelist+0xfce/0x2f80 mm/page_alloc.c:3474
__alloc_pages_noprof+0x223/0x25a0 mm/page_alloc.c:4751
alloc_pages_mpol_noprof+0x2c9/0x610 mm/mempolicy.c:2265
alloc_slab_page mm/slub.c:2408 [inline]
allocate_slab mm/slub.c:2574 [inline]
new_slab+0x2c9/0x410 mm/slub.c:2627
___slab_alloc+0xd1d/0x16e0 mm/slub.c:3815
__slab_alloc.constprop.0+0x56/0xb0 mm/slub.c:3905
__slab_alloc_node mm/slub.c:3980 [inline]
slab_alloc_node mm/slub.c:4141 [inline]
__kmalloc_cache_noprof+0xf6/0x420 mm/slub.c:4309

kmalloc_noprof include/linux/slab.h:901 [inline]
kzalloc_noprof include/linux/slab.h:1037 [inline]

afs_alloc_call+0x4f/0x4a0 fs/afs/rxrpc.c:144
afs_charge_preallocation+0xff/0x330 fs/afs/rxrpc.c:736
afs_open_socket+0x298/0x350 fs/afs/rxrpc.c:95
afs_net_init+0x95d/0xc60 fs/afs/main.c:123
ops_init+0x1df/0x5f0 net/core/net_namespace.c:138
setup_net+0x21f/0x860 net/core/net_namespace.c:362
copy_net_ns+0x2b4/0x6b0 net/core/net_namespace.c:500
create_new_namespaces+0x3ea/0xad0 kernel/nsproxy.c:110
page last free pid 5853 tgid 5853 stack trace:

reset_page_owner include/linux/page_owner.h:25 [inline]
free_pages_prepare mm/page_alloc.c:1127 [inline]

free_unref_page+0x661/0x1080 mm/page_alloc.c:2657
vfree+0x17a/0x890 mm/vmalloc.c:3382
kcov_put kernel/kcov.c:439 [inline]
kcov_put+0x2a/0x40 kernel/kcov.c:435
kcov_close+0xd/0x20 kernel/kcov.c:535

__fput+0x3f8/0xb60 fs/file_table.c:450
task_work_run+0x14e/0x250 kernel/task_work.c:239
exit_task_work include/linux/task_work.h:43 [inline]

do_exit+0xadd/0x2d70 kernel/exit.c:938
do_group_exit+0xd3/0x2a0 kernel/exit.c:1087
get_signal+0x2576/0x2610 kernel/signal.c:3016

arch_do_signal_or_restart+0x90/0x7e0 arch/x86/kernel/signal.c:337
exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
exit_to_user_mode_prepare include/linux/entry-common.h:329 [inline]
__syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
syscall_exit_to_user_mode+0x150/0x2a0 kernel/entry/common.c:218
do_syscall_64+0xda/0x250 arch/x86/entry/common.c:89
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:

ffff8880723fdf00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff8880723fdf80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8880723fe000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8880723fe080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8880723fe100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


Tested on:

commit: 8e1aa296 Bluetooth: vhci: fix a uaf in force_devcd_write
git tree: https://github.com/ea1davis/linux bt/syz
console output: https://syzkaller.appspot.com/x/log.txt?x=171500b0580000
kernel config: https://syzkaller.appspot.com/x/.config?x=e8d97faf7b870c89

dashboard link: https://syzkaller.appspot.com/bug?extid=bc71245e56f06e3127b7
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

Note: no patches were applied.

[syzbot]

For archival purposes, forwarding an incoming command email to
linux-...@vger.kernel.org, syzkall...@googlegroups.com.

***

Subject:
Author: ma...@getstate.dev

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by: syzbot+bc7124...@syzkaller.appspotmail.com
Tested-by: syzbot+bc7124...@syzkaller.appspotmail.com

Tested on:

commit: 9b2ffa61 Merge tag 'mtd/fixes-for-6.13-rc5' of git://g..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15749adf980000
kernel config: https://syzkaller.appspot.com/x/.config?x=c078001e66e4a17e

dashboard link: https://syzkaller.appspot.com/bug?extid=bc71245e56f06e3127b7
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=174362f8580000

Note: testing is done by a robot and is best-effort only.

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: 4c06e63b9203 Merge tag 'for-6.16-rc4-tag' of git://git.ker..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11594c8c580000
kernel config: https://syzkaller.appspot.com/x/.config?x=9887aa986c36cc50

dashboard link: https://syzkaller.appspot.com/bug?extid=bc71245e56f06e3127b7
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=139dac8c580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=14b90f70580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/25b7407ad24e/disk-4c06e63b.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/b2ae62cd2161/vmlinux-4c06e63b.xz
kernel image: https://storage.googleapis.com/syzbot-assets/3cecae8778af/bzImage-4c06e63b.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+bc7124...@syzkaller.appspotmail.com

==================================================================

BUG: KASAN: slab-use-after-free in force_devcd_write+0x312/0x340 drivers/bluetooth/hci_vhci.c:327
Read of size 8 at addr ffff888025726000 by task syz.0.616/6743

CPU: 0 UID: 0 PID: 6743 Comm: syz.0.616 Not tainted 6.16.0-rc4-syzkaller-00123-g4c06e63b9203 #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025

Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120

print_address_description mm/kasan/report.c:408 [inline]
print_report+0xcd/0x680 mm/kasan/report.c:521
kasan_report+0xe0/0x110 mm/kasan/report.c:634
force_devcd_write+0x312/0x340 drivers/bluetooth/hci_vhci.c:327
full_proxy_write+0x13c/0x200 fs/debugfs/file.c:398
vfs_write+0x29d/0x1150 fs/read_write.c:684
ksys_write+0x12a/0x250 fs/read_write.c:738
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xcd/0x490 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f8d06f8e929

Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48

RSP: 002b:00007fff1271b2f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f8d071b5fa0 RCX: 00007f8d06f8e929

RDX: 000000000000000e RSI: 0000000000000000 RDI: 0000000000000003

RBP: 00007f8d07010b39 R08: 0000000000000000 R09: 0000000000000000

R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000

R13: 00007f8d071b5fa0 R14: 00007f8d071b5fa0 R15: 0000000000000003
</TASK>

Allocated by task 5958:

kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
kasan_save_track+0x14/0x30 mm/kasan/common.c:68
poison_kmalloc_redzone mm/kasan/common.c:377 [inline]
__kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:394

kmalloc_noprof include/linux/slab.h:905 [inline]
kzalloc_noprof include/linux/slab.h:1039 [inline]
vhci_open+0x4c/0x430 drivers/bluetooth/hci_vhci.c:635
misc_open+0x35a/0x420 drivers/char/misc.c:161
chrdev_open+0x231/0x6a0 fs/char_dev.c:414
do_dentry_open+0x744/0x1c10 fs/open.c:964
vfs_open+0x82/0x3f0 fs/open.c:1094
do_open fs/namei.c:3896 [inline]
path_openat+0x1de4/0x2cb0 fs/namei.c:4055
do_filp_open+0x20b/0x470 fs/namei.c:4082
do_sys_openat2+0x11b/0x1d0 fs/open.c:1437
do_sys_open fs/open.c:1452 [inline]
__do_sys_openat fs/open.c:1468 [inline]
__se_sys_openat fs/open.c:1463 [inline]
__x64_sys_openat+0x174/0x210 fs/open.c:1463
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xcd/0x490 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 5958:

kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
kasan_save_track+0x14/0x30 mm/kasan/common.c:68

kasan_save_free_info+0x3b/0x60 mm/kasan/generic.c:576

poison_slab_object mm/kasan/common.c:247 [inline]
__kasan_slab_free+0x51/0x70 mm/kasan/common.c:264
kasan_slab_free include/linux/kasan.h:233 [inline]

slab_free_hook mm/slub.c:2381 [inline]
slab_free mm/slub.c:4643 [inline]
kfree+0x2b4/0x4d0 mm/slub.c:4842
vhci_release+0xbb/0xf0 drivers/bluetooth/hci_vhci.c:671
__fput+0x402/0xb70 fs/file_table.c:465
task_work_run+0x14d/0x240 kernel/task_work.c:227
exit_task_work include/linux/task_work.h:40 [inline]
do_exit+0x86c/0x2bd0 kernel/exit.c:964
do_group_exit+0xd3/0x2a0 kernel/exit.c:1105
get_signal+0x2673/0x26d0 kernel/signal.c:3034
arch_do_signal_or_restart+0x8f/0x790 arch/x86/kernel/signal.c:337
exit_to_user_mode_loop+0x84/0x110 kernel/entry/common.c:111
exit_to_user_mode_prepare include/linux/entry-common.h:330 [inline]
syscall_exit_to_user_mode_work include/linux/entry-common.h:414 [inline]
syscall_exit_to_user_mode include/linux/entry-common.h:449 [inline]
do_syscall_64+0x3f6/0x490 arch/x86/entry/syscall_64.c:100
entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff888025726000

which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 0 bytes inside of

freed 1024-byte region [ffff888025726000, ffff888025726400)

The buggy address belongs to the physical page:

page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x25720

head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)

raw: 00fff00000000040 ffff88801b841dc0 dead000000000100 dead000000000122
raw: 0000000000000000 0000000000100010 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88801b841dc0 dead000000000100 dead000000000122
head: 0000000000000000 0000000000100010 00000000f5000000 0000000000000000
head: 00fff00000000003 ffffea000095c801 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000008

page dumped because: kasan: bad access detected
page_owner tracks the page as allocated

page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5605, tgid 5605 (dhcpcd-run-hook), ts 69092117143, free_ts 69052522693
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x1c0/0x230 mm/page_alloc.c:1704
prep_new_page mm/page_alloc.c:1712 [inline]
get_page_from_freelist+0x1321/0x3890 mm/page_alloc.c:3669
__alloc_frozen_pages_noprof+0x261/0x23f0 mm/page_alloc.c:4959
alloc_pages_mpol+0x1fb/0x550 mm/mempolicy.c:2419
alloc_slab_page mm/slub.c:2451 [inline]
allocate_slab mm/slub.c:2619 [inline]
new_slab+0x23b/0x330 mm/slub.c:2673
___slab_alloc+0xd9c/0x1940 mm/slub.c:3859
__slab_alloc.constprop.0+0x56/0xb0 mm/slub.c:3949
__slab_alloc_node mm/slub.c:4024 [inline]
slab_alloc_node mm/slub.c:4185 [inline]
__do_kmalloc_node mm/slub.c:4327 [inline]
__kmalloc_noprof+0x2f2/0x510 mm/slub.c:4340
kmalloc_noprof include/linux/slab.h:909 [inline]
load_elf_phdrs+0x102/0x210 fs/binfmt_elf.c:525
load_elf_binary+0x14c1/0x4f00 fs/binfmt_elf.c:954
search_binary_handler fs/exec.c:1665 [inline]
exec_binprm fs/exec.c:1697 [inline]
bprm_execve fs/exec.c:1749 [inline]
bprm_execve+0x8c3/0x1650 fs/exec.c:1725
do_execveat_common.isra.0+0x4a5/0x610 fs/exec.c:1855
do_execve fs/exec.c:1929 [inline]
__do_sys_execve fs/exec.c:2005 [inline]
__se_sys_execve fs/exec.c:2000 [inline]
__x64_sys_execve+0x8e/0xb0 fs/exec.c:2000
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xcd/0x490 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
page last free pid 5601 tgid 5601 stack trace:
reset_page_owner include/linux/page_owner.h:25 [inline]
free_pages_prepare mm/page_alloc.c:1248 [inline]
__free_frozen_pages+0x7fe/0x1180 mm/page_alloc.c:2706
discard_slab mm/slub.c:2717 [inline]
__put_partials+0x16d/0x1c0 mm/slub.c:3186
qlink_free mm/kasan/quarantine.c:163 [inline]
qlist_free_all+0x4d/0x120 mm/kasan/quarantine.c:179

kasan_quarantine_reduce+0x195/0x1e0 mm/kasan/quarantine.c:286
__kasan_slab_alloc+0x69/0x90 mm/kasan/common.c:329
kasan_slab_alloc include/linux/kasan.h:250 [inline]

slab_post_alloc_hook mm/slub.c:4148 [inline]
slab_alloc_node mm/slub.c:4197 [inline]
__do_kmalloc_node mm/slub.c:4327 [inline]
__kmalloc_noprof+0x1d4/0x510 mm/slub.c:4340
kmalloc_noprof include/linux/slab.h:909 [inline]
tomoyo_realpath_from_path+0xc2/0x6e0 security/tomoyo/realpath.c:251
tomoyo_get_realpath security/tomoyo/file.c:151 [inline]
tomoyo_path_perm+0x274/0x460 security/tomoyo/file.c:822
security_inode_getattr+0x116/0x290 security/security.c:2377
vfs_getattr fs/stat.c:259 [inline]
vfs_fstat+0x4b/0xe0 fs/stat.c:281
__do_sys_newfstat+0x87/0x100 fs/stat.c:555
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xcd/0x490 arch/x86/entry/syscall_64.c:94

entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:

ffff888025725f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff888025725f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff888025726000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888025726080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888025726100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---

[Hillf Danton]

> Date: Fri, 04 Jul 2025 02:39:26 -0700

> syzbot has found a reproducer for the following issue on:
>
> HEAD commit: 4c06e63b9203 Merge tag 'for-6.16-rc4-tag' of git://git.ker..
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=11594c8c580000
> kernel config: https://syzkaller.appspot.com/x/.config?x=9887aa986c36cc50
> dashboard link: https://syzkaller.appspot.com/bug?extid=bc71245e56f06e3127b7
> compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=139dac8c580000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=14b90f70580000

#syz test

--- x/drivers/bluetooth/hci_vhci.c
+++ y/drivers/bluetooth/hci_vhci.c
@@ -320,6 +320,7 @@ static inline void force_devcd_timeout(s
#endif
}

+static DEFINE_MUTEX(vhci_release_lock);
static ssize_t force_devcd_write(struct file *file, const char __user *user_buf,
size_t count, loff_t *ppos)
{
@@ -343,6 +344,17 @@ static ssize_t force_devcd_write(struct
return -ENOMEM;
skb_put_data(skb, &dump_data.data, data_size);

+ if (!mutex_trylock(&vhci_release_lock)) {
+out:
+ kfree_skb(skb);
+ return -EBUSY;
+ }
+ data = file->private_data;
+ if (!data) {
+ mutex_unlock(&vhci_release_lock);
+ goto out;
+ }
+ hdev = data->hdev;
hci_devcd_register(hdev, vhci_coredump, vhci_coredump_hdr, NULL);

/* Force the devcoredump timeout */
@@ -352,6 +364,7 @@ static ssize_t force_devcd_write(struct
ret = hci_devcd_init(hdev, skb->len);
if (ret) {
BT_ERR("Failed to generate devcoredump");
+ mutex_unlock(&vhci_release_lock);
kfree_skb(skb);
return ret;
}
@@ -369,9 +382,11 @@ static ssize_t force_devcd_write(struct
/* Do nothing */
break;
default:
+ mutex_unlock(&vhci_release_lock);
return -EINVAL;
}

+ mutex_unlock(&vhci_release_lock);
return count;
}

@@ -656,6 +671,7 @@ static int vhci_release(struct inode *in
struct vhci_data *data = file->private_data;
struct hci_dev *hdev;

+ mutex_lock(&vhci_release_lock);
cancel_delayed_work_sync(&data->open_timeout);
flush_work(&data->suspend_work);

@@ -669,6 +685,7 @@ static int vhci_release(struct inode *in
skb_queue_purge(&data->readq);
file->private_data = NULL;
kfree(data);
+ mutex_unlock(&vhci_release_lock);

return 0;
}
--

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
KASAN: slab-use-after-free Read in force_devcd_write

==================================================================
BUG: KASAN: slab-use-after-free in force_devcd_write+0x3ab/0x3d0 drivers/bluetooth/hci_vhci.c:357
Read of size 8 at addr ffff88807b7c2000 by task syz.0.616/8009

CPU: 1 UID: 0 PID: 8009 Comm: syz.0.616 Not tainted 6.16.0-rc4-syzkaller-g4c06e63b9203-dirty #0 PREEMPT(full)

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
print_address_description mm/kasan/report.c:408 [inline]
print_report+0xcd/0x680 mm/kasan/report.c:521
kasan_report+0xe0/0x110 mm/kasan/report.c:634

force_devcd_write+0x3ab/0x3d0 drivers/bluetooth/hci_vhci.c:357

full_proxy_write+0x13c/0x200 fs/debugfs/file.c:398
vfs_write+0x29d/0x1150 fs/read_write.c:684
ksys_write+0x12a/0x250 fs/read_write.c:738
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xcd/0x490 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

RIP: 0033:0x7f3d27b8e929

Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48

RSP: 002b:00007f3d28949038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f3d27db5fa0 RCX: 00007f3d27b8e929

RDX: 000000000000000e RSI: 0000000000000000 RDI: 0000000000000003

RBP: 00007f3d27c10b39 R08: 0000000000000000 R09: 0000000000000000

R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000

R13: 0000000000000000 R14: 00007f3d27db5fa0 R15: 00007ffd515bb5e8
</TASK>

Allocated by task 6459:

kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
kasan_save_track+0x14/0x30 mm/kasan/common.c:68
poison_kmalloc_redzone mm/kasan/common.c:377 [inline]
__kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:394
kmalloc_noprof include/linux/slab.h:905 [inline]
kzalloc_noprof include/linux/slab.h:1039 [inline]

vhci_open+0x4c/0x430 drivers/bluetooth/hci_vhci.c:650

misc_open+0x35a/0x420 drivers/char/misc.c:161
chrdev_open+0x231/0x6a0 fs/char_dev.c:414
do_dentry_open+0x744/0x1c10 fs/open.c:964
vfs_open+0x82/0x3f0 fs/open.c:1094
do_open fs/namei.c:3896 [inline]
path_openat+0x1de4/0x2cb0 fs/namei.c:4055
do_filp_open+0x20b/0x470 fs/namei.c:4082
do_sys_openat2+0x11b/0x1d0 fs/open.c:1437
do_sys_open fs/open.c:1452 [inline]
__do_sys_openat fs/open.c:1468 [inline]
__se_sys_openat fs/open.c:1463 [inline]
__x64_sys_openat+0x174/0x210 fs/open.c:1463
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xcd/0x490 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 6459:

kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
kasan_save_track+0x14/0x30 mm/kasan/common.c:68
kasan_save_free_info+0x3b/0x60 mm/kasan/generic.c:576
poison_slab_object mm/kasan/common.c:247 [inline]
__kasan_slab_free+0x51/0x70 mm/kasan/common.c:264
kasan_slab_free include/linux/kasan.h:233 [inline]
slab_free_hook mm/slub.c:2381 [inline]
slab_free mm/slub.c:4643 [inline]
kfree+0x2b4/0x4d0 mm/slub.c:4842

vhci_release+0xcd/0x110 drivers/bluetooth/hci_vhci.c:687

__fput+0x402/0xb70 fs/file_table.c:465
task_work_run+0x14d/0x240 kernel/task_work.c:227
exit_task_work include/linux/task_work.h:40 [inline]
do_exit+0x86c/0x2bd0 kernel/exit.c:964
do_group_exit+0xd3/0x2a0 kernel/exit.c:1105
get_signal+0x2673/0x26d0 kernel/signal.c:3034
arch_do_signal_or_restart+0x8f/0x790 arch/x86/kernel/signal.c:337
exit_to_user_mode_loop+0x84/0x110 kernel/entry/common.c:111
exit_to_user_mode_prepare include/linux/entry-common.h:330 [inline]
syscall_exit_to_user_mode_work include/linux/entry-common.h:414 [inline]
syscall_exit_to_user_mode include/linux/entry-common.h:449 [inline]
do_syscall_64+0x3f6/0x490 arch/x86/entry/syscall_64.c:100
entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff88807b7c2000

which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 0 bytes inside of

freed 1024-byte region [ffff88807b7c2000, ffff88807b7c2400)

The buggy address belongs to the physical page:

page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x7b7c0

head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0

anon flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000040 ffff88801b841dc0 0000000000000000 dead000000000001

raw: 0000000000000000 0000000000100010 00000000f5000000 0000000000000000

head: 00fff00000000040 ffff88801b841dc0 0000000000000000 dead000000000001

head: 0000000000000000 0000000000100010 00000000f5000000 0000000000000000

head: 00fff00000000003 ffffea0001edf001 00000000ffffffff 00000000ffffffff

head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000008
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated

page last allocated via order 3, migratetype Unmovable, gfp_mask 0x52820(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP), pid 57, tgid 57 (kworker/u8:4), ts 136316981402, free_ts 132545952720

set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x1c0/0x230 mm/page_alloc.c:1704
prep_new_page mm/page_alloc.c:1712 [inline]
get_page_from_freelist+0x1321/0x3890 mm/page_alloc.c:3669
__alloc_frozen_pages_noprof+0x261/0x23f0 mm/page_alloc.c:4959
alloc_pages_mpol+0x1fb/0x550 mm/mempolicy.c:2419
alloc_slab_page mm/slub.c:2451 [inline]
allocate_slab mm/slub.c:2619 [inline]
new_slab+0x23b/0x330 mm/slub.c:2673
___slab_alloc+0xd9c/0x1940 mm/slub.c:3859
__slab_alloc.constprop.0+0x56/0xb0 mm/slub.c:3949
__slab_alloc_node mm/slub.c:4024 [inline]
slab_alloc_node mm/slub.c:4185 [inline]
__do_kmalloc_node mm/slub.c:4327 [inline]
__kmalloc_noprof+0x2f2/0x510 mm/slub.c:4340
kmalloc_noprof include/linux/slab.h:909 [inline]

kzalloc_noprof include/linux/slab.h:1039 [inline]
neigh_alloc net/core/neighbour.c:473 [inline]
___neigh_create+0x14e6/0x28c0 net/core/neighbour.c:607
ip6_finish_output2+0x1299/0x2020 net/ipv6/ip6_output.c:132
__ip6_finish_output net/ipv6/ip6_output.c:215 [inline]
ip6_finish_output+0x3f9/0x1360 net/ipv6/ip6_output.c:226
NF_HOOK_COND include/linux/netfilter.h:306 [inline]
ip6_output+0x1f9/0x540 net/ipv6/ip6_output.c:247
dst_output include/net/dst.h:459 [inline]
NF_HOOK include/linux/netfilter.h:317 [inline]
ndisc_send_skb+0xa91/0x1e40 net/ipv6/ndisc.c:513
ndisc_send_rs+0x129/0x670 net/ipv6/ndisc.c:723
addrconf_dad_completed+0x49d/0x10d0 net/ipv6/addrconf.c:4364
addrconf_dad_work+0x84d/0x14e0 net/ipv6/addrconf.c:4272
page last free pid 6349 tgid 6349 stack trace:

reset_page_owner include/linux/page_owner.h:25 [inline]
free_pages_prepare mm/page_alloc.c:1248 [inline]
__free_frozen_pages+0x7fe/0x1180 mm/page_alloc.c:2706

vfree+0x1fd/0xb50 mm/vmalloc.c:3426
kcov_put kernel/kcov.c:439 [inline]
kcov_put kernel/kcov.c:435 [inline]
kcov_close+0x34/0x60 kernel/kcov.c:535

__fput+0x402/0xb70 fs/file_table.c:465
task_work_run+0x14d/0x240 kernel/task_work.c:227
exit_task_work include/linux/task_work.h:40 [inline]
do_exit+0x86c/0x2bd0 kernel/exit.c:964
do_group_exit+0xd3/0x2a0 kernel/exit.c:1105
get_signal+0x2673/0x26d0 kernel/signal.c:3034
arch_do_signal_or_restart+0x8f/0x790 arch/x86/kernel/signal.c:337
exit_to_user_mode_loop+0x84/0x110 kernel/entry/common.c:111
exit_to_user_mode_prepare include/linux/entry-common.h:330 [inline]
syscall_exit_to_user_mode_work include/linux/entry-common.h:414 [inline]
syscall_exit_to_user_mode include/linux/entry-common.h:449 [inline]
do_syscall_64+0x3f6/0x490 arch/x86/entry/syscall_64.c:100
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:

ffff88807b7c1f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88807b7c1f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88807b7c2000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88807b7c2080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88807b7c2100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


Tested on:

commit: 4c06e63b Merge tag 'for-6.16-rc4-tag' of git://git.ker..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10786c8c580000

kernel config: https://syzkaller.appspot.com/x/.config?x=9887aa986c36cc50
dashboard link: https://syzkaller.appspot.com/bug?extid=bc71245e56f06e3127b7
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=108473d4580000

[Hillf Danton]

> Date: Fri, 04 Jul 2025 02:39:26 -0700

> syzbot has found a reproducer for the following issue on:
>
> HEAD commit: 4c06e63b9203 Merge tag 'for-6.16-rc4-tag' of git://git.ker..
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=11594c8c580000
> kernel config: https://syzkaller.appspot.com/x/.config?x=9887aa986c36cc50
> dashboard link: https://syzkaller.appspot.com/bug?extid=bc71245e56f06e3127b7
> compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=139dac8c580000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=14b90f70580000

#syz test

--- x/drivers/bluetooth/hci_vhci.c
+++ y/drivers/bluetooth/hci_vhci.c

@@ -320,11 +320,12 @@ static inline void force_devcd_timeout(s

#endif
}

+static DEFINE_MUTEX(vhci_release_lock);
static ssize_t force_devcd_write(struct file *file, const char __user *user_buf,
size_t count, loff_t *ppos)
{

- struct vhci_data *data = file->private_data;
- struct hci_dev *hdev = data->hdev;
+ struct vhci_data *data;
+ struct hci_dev *hdev;
struct sk_buff *skb = NULL;
struct devcoredump_test_data dump_data;
size_t data_size;

@@ -656,6 +671,8 @@ static int vhci_release(struct inode *in

struct vhci_data *data = file->private_data;
struct hci_dev *hdev;

+ mutex_lock(&vhci_release_lock);

+ data = file->private_data;

cancel_delayed_work_sync(&data->open_timeout);
flush_work(&data->suspend_work);

@@ -669,6 +686,7 @@ static int vhci_release(struct inode *in

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
KASAN: slab-use-after-free Read in force_devcd_write

==================================================================
BUG: KASAN: slab-use-after-free in force_devcd_write+0x3ab/0x3d0 drivers/bluetooth/hci_vhci.c:357

Read of size 8 at addr ffff88807ab4c800 by task syz.0.616/8054

CPU: 1 UID: 0 PID: 8054 Comm: syz.0.616 Not tainted 6.16.0-rc4-syzkaller-g4c06e63b9203-dirty #0 PREEMPT(full)

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
print_address_description mm/kasan/report.c:408 [inline]
print_report+0xcd/0x680 mm/kasan/report.c:521
kasan_report+0xe0/0x110 mm/kasan/report.c:634
force_devcd_write+0x3ab/0x3d0 drivers/bluetooth/hci_vhci.c:357
full_proxy_write+0x13c/0x200 fs/debugfs/file.c:398
vfs_write+0x29d/0x1150 fs/read_write.c:684
ksys_write+0x12a/0x250 fs/read_write.c:738
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xcd/0x490 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

RIP: 0033:0x7f6d5398e929

Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48

RSP: 002b:00007f6d547a1038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f6d53bb5fa0 RCX: 00007f6d5398e929

RDX: 000000000000000e RSI: 0000000000000000 RDI: 0000000000000003

RBP: 00007f6d53a10b39 R08: 0000000000000000 R09: 0000000000000000

R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000

R13: 0000000000000000 R14: 00007f6d53bb5fa0 R15: 00007ffd8bc9db28
</TASK>

Allocated by task 6589:

kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
kasan_save_track+0x14/0x30 mm/kasan/common.c:68
poison_kmalloc_redzone mm/kasan/common.c:377 [inline]
__kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:394
kmalloc_noprof include/linux/slab.h:905 [inline]
kzalloc_noprof include/linux/slab.h:1039 [inline]
vhci_open+0x4c/0x430 drivers/bluetooth/hci_vhci.c:650
misc_open+0x35a/0x420 drivers/char/misc.c:161
chrdev_open+0x231/0x6a0 fs/char_dev.c:414
do_dentry_open+0x744/0x1c10 fs/open.c:964
vfs_open+0x82/0x3f0 fs/open.c:1094
do_open fs/namei.c:3896 [inline]
path_openat+0x1de4/0x2cb0 fs/namei.c:4055
do_filp_open+0x20b/0x470 fs/namei.c:4082
do_sys_openat2+0x11b/0x1d0 fs/open.c:1437
do_sys_open fs/open.c:1452 [inline]
__do_sys_openat fs/open.c:1468 [inline]
__se_sys_openat fs/open.c:1463 [inline]
__x64_sys_openat+0x174/0x210 fs/open.c:1463
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xcd/0x490 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 6589:

kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
kasan_save_track+0x14/0x30 mm/kasan/common.c:68
kasan_save_free_info+0x3b/0x60 mm/kasan/generic.c:576
poison_slab_object mm/kasan/common.c:247 [inline]
__kasan_slab_free+0x51/0x70 mm/kasan/common.c:264
kasan_slab_free include/linux/kasan.h:233 [inline]
slab_free_hook mm/slub.c:2381 [inline]
slab_free mm/slub.c:4643 [inline]
kfree+0x2b4/0x4d0 mm/slub.c:4842

vhci_release+0xcd/0x110 drivers/bluetooth/hci_vhci.c:688

__fput+0x402/0xb70 fs/file_table.c:465
task_work_run+0x14d/0x240 kernel/task_work.c:227
exit_task_work include/linux/task_work.h:40 [inline]
do_exit+0x86c/0x2bd0 kernel/exit.c:964
do_group_exit+0xd3/0x2a0 kernel/exit.c:1105
get_signal+0x2673/0x26d0 kernel/signal.c:3034
arch_do_signal_or_restart+0x8f/0x790 arch/x86/kernel/signal.c:337
exit_to_user_mode_loop+0x84/0x110 kernel/entry/common.c:111
exit_to_user_mode_prepare include/linux/entry-common.h:330 [inline]
syscall_exit_to_user_mode_work include/linux/entry-common.h:414 [inline]
syscall_exit_to_user_mode include/linux/entry-common.h:449 [inline]
do_syscall_64+0x3f6/0x490 arch/x86/entry/syscall_64.c:100
entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff88807ab4c800

which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 0 bytes inside of

freed 1024-byte region [ffff88807ab4c800, ffff88807ab4cc00)

The buggy address belongs to the physical page:

page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x7ab48

head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
anon flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)

raw: 00fff00000000040 ffff88801b841dc0 0000000000000000 0000000000000001

raw: 0000000000000000 0000000000100010 00000000f5000000 0000000000000000

head: 00fff00000000040 ffff88801b841dc0 0000000000000000 0000000000000001

head: 0000000000000000 0000000000100010 00000000f5000000 0000000000000000

head: 00fff00000000003 ffffea0001ead201 00000000ffffffff 00000000ffffffff

head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000008
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated

page last allocated via order 3, migratetype Unmovable, gfp_mask 0x52820(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP), pid 2954, tgid 2954 (kworker/u8:8), ts 94650347230, free_ts 94499980362

set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x1c0/0x230 mm/page_alloc.c:1704
prep_new_page mm/page_alloc.c:1712 [inline]
get_page_from_freelist+0x1321/0x3890 mm/page_alloc.c:3669
__alloc_frozen_pages_noprof+0x261/0x23f0 mm/page_alloc.c:4959
alloc_pages_mpol+0x1fb/0x550 mm/mempolicy.c:2419
alloc_slab_page mm/slub.c:2451 [inline]
allocate_slab mm/slub.c:2619 [inline]
new_slab+0x23b/0x330 mm/slub.c:2673
___slab_alloc+0xd9c/0x1940 mm/slub.c:3859
__slab_alloc.constprop.0+0x56/0xb0 mm/slub.c:3949
__slab_alloc_node mm/slub.c:4024 [inline]
slab_alloc_node mm/slub.c:4185 [inline]
__do_kmalloc_node mm/slub.c:4327 [inline]
__kmalloc_noprof+0x2f2/0x510 mm/slub.c:4340
kmalloc_noprof include/linux/slab.h:909 [inline]
kzalloc_noprof include/linux/slab.h:1039 [inline]

ieee802_11_parse_elems_full+0x1d7/0x3780 net/mac80211/parse.c:1013
ieee802_11_parse_elems_crc net/mac80211/ieee80211_i.h:2414 [inline]
ieee802_11_parse_elems net/mac80211/ieee80211_i.h:2421 [inline]
ieee80211_inform_bss+0x10b/0x1140 net/mac80211/scan.c:79
rdev_inform_bss net/wireless/rdev-ops.h:418 [inline]
cfg80211_inform_single_bss_data+0x8ea/0x1df0 net/wireless/scan.c:2367
cfg80211_inform_bss_data+0x224/0x3bc0 net/wireless/scan.c:3222
cfg80211_inform_bss_frame_data+0x26f/0x750 net/wireless/scan.c:3313
ieee80211_bss_info_update+0x310/0xab0 net/mac80211/scan.c:226
ieee80211_rx_bss_info net/mac80211/ibss.c:1094 [inline]
ieee80211_rx_mgmt_probe_beacon net/mac80211/ibss.c:1573 [inline]
ieee80211_ibss_rx_queued_mgmt+0x1905/0x2fd0 net/mac80211/ibss.c:1600
ieee80211_iface_process_skb net/mac80211/iface.c:1668 [inline]
ieee80211_iface_work+0xbf4/0x1020 net/mac80211/iface.c:1722
page last free pid 2938 tgid 2938 stack trace:

reset_page_owner include/linux/page_owner.h:25 [inline]
free_pages_prepare mm/page_alloc.c:1248 [inline]
__free_frozen_pages+0x7fe/0x1180 mm/page_alloc.c:2706

discard_slab mm/slub.c:2717 [inline]
__put_partials+0x16d/0x1c0 mm/slub.c:3186
qlink_free mm/kasan/quarantine.c:163 [inline]
qlist_free_all+0x4d/0x120 mm/kasan/quarantine.c:179
kasan_quarantine_reduce+0x195/0x1e0 mm/kasan/quarantine.c:286
__kasan_slab_alloc+0x69/0x90 mm/kasan/common.c:329
kasan_slab_alloc include/linux/kasan.h:250 [inline]
slab_post_alloc_hook mm/slub.c:4148 [inline]
slab_alloc_node mm/slub.c:4197 [inline]

kmem_cache_alloc_node_noprof+0x1d5/0x3b0 mm/slub.c:4249
__alloc_skb+0x2b2/0x380 net/core/skbuff.c:660
alloc_skb include/linux/skbuff.h:1336 [inline]
nlmsg_new include/net/netlink.h:1041 [inline]
br_vlan_notify+0x15b/0x8c0 net/bridge/br_vlan.c:1933
br_vlan_bridge_event+0x343/0x5c0 net/bridge/br_vlan.c:1772
br_device_event+0x3d8/0xa00 net/bridge/br.c:40
notifier_call_chain+0xbc/0x410 kernel/notifier.c:85
call_netdevice_notifiers_info+0xbe/0x140 net/core/dev.c:2230
call_netdevice_notifiers_extack net/core/dev.c:2268 [inline]
call_netdevice_notifiers net/core/dev.c:2282 [inline]
unregister_netdevice_many_notify+0xf9d/0x2700 net/core/dev.c:12077
ops_exit_rtnl_list net/core/net_namespace.c:188 [inline]
ops_undo_list+0x8fc/0xab0 net/core/net_namespace.c:249
cleanup_net+0x408/0x890 net/core/net_namespace.c:686
process_one_work+0x9cf/0x1b70 kernel/workqueue.c:3238

Memory state around the buggy address:

ffff88807ab4c700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88807ab4c780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88807ab4c800: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88807ab4c880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88807ab4c900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


Tested on:

commit: 4c06e63b Merge tag 'for-6.16-rc4-tag' of git://git.ker..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15708f70580000

kernel config: https://syzkaller.appspot.com/x/.config?x=9887aa986c36cc50
dashboard link: https://syzkaller.appspot.com/bug?extid=bc71245e56f06e3127b7
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=119473d4580000

[Hillf Danton]

> Date: Fri, 04 Jul 2025 02:39:26 -0700

> syzbot has found a reproducer for the following issue on:
>
> HEAD commit: 4c06e63b9203 Merge tag 'for-6.16-rc4-tag' of git://git.ker..
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=11594c8c580000
> kernel config: https://syzkaller.appspot.com/x/.config?x=9887aa986c36cc50
> dashboard link: https://syzkaller.appspot.com/bug?extid=bc71245e56f06e3127b7
> compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=139dac8c580000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=14b90f70580000

#syz test

--- x/drivers/bluetooth/hci_vhci.c
+++ y/drivers/bluetooth/hci_vhci.c

@@ -320,11 +320,13 @@ static inline void force_devcd_timeout(s
#endif
}

+static DEFINE_MUTEX(vhci_release_lock);
+static int released = 0;

static ssize_t force_devcd_write(struct file *file, const char __user *user_buf,
size_t count, loff_t *ppos)
{
- struct vhci_data *data = file->private_data;
- struct hci_dev *hdev = data->hdev;
+ struct vhci_data *data;
+ struct hci_dev *hdev;
struct sk_buff *skb = NULL;
struct devcoredump_test_data dump_data;
size_t data_size;

@@ -343,6 +345,21 @@ static ssize_t force_devcd_write(struct

return -ENOMEM;
skb_put_data(skb, &dump_data.data, data_size);

+ if (!mutex_trylock(&vhci_release_lock)) {
+out:
+ kfree_skb(skb);
+ return -EBUSY;
+ }

+ if (released) {

+ mutex_unlock(&vhci_release_lock);
+ goto out;
+ }
+ data = file->private_data;
+ if (!data) {
+ mutex_unlock(&vhci_release_lock);
+ goto out;
+ }
+ hdev = data->hdev;
hci_devcd_register(hdev, vhci_coredump, vhci_coredump_hdr, NULL);

/* Force the devcoredump timeout */

@@ -352,6 +369,7 @@ static ssize_t force_devcd_write(struct

ret = hci_devcd_init(hdev, skb->len);
if (ret) {
BT_ERR("Failed to generate devcoredump");
+ mutex_unlock(&vhci_release_lock);
kfree_skb(skb);
return ret;
}

@@ -369,9 +387,11 @@ static ssize_t force_devcd_write(struct

/* Do nothing */
break;
default:
+ mutex_unlock(&vhci_release_lock);
return -EINVAL;
}

+ mutex_unlock(&vhci_release_lock);
return count;
}

@@ -656,6 +676,8 @@ static int vhci_release(struct inode *in

struct vhci_data *data = file->private_data;
struct hci_dev *hdev;

+ mutex_lock(&vhci_release_lock);
+ data = file->private_data;
cancel_delayed_work_sync(&data->open_timeout);
flush_work(&data->suspend_work);

@@ -669,6 +691,8 @@ static int vhci_release(struct inode *in

skb_queue_purge(&data->readq);
file->private_data = NULL;
kfree(data);

+ released++;

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by: syzbot+bc7124...@syzkaller.appspotmail.com
Tested-by: syzbot+bc7124...@syzkaller.appspotmail.com

Tested on:

commit: 4c06e63b Merge tag 'for-6.16-rc4-tag' of git://git.ker..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13cf4c8c580000

kernel config: https://syzkaller.appspot.com/x/.config?x=9887aa986c36cc50
dashboard link: https://syzkaller.appspot.com/bug?extid=bc71245e56f06e3127b7
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=16888f70580000