[syzbot] [bluetooth?] KASAN: slab-use-after-free Write in sco_chan_del

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syzbot

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May 15, 2023, 8:47:39 AM5/15/23
to da...@davemloft.net, edum...@google.com, johan....@gmail.com, ku...@kernel.org, linux-b...@vger.kernel.org, linux-...@vger.kernel.org, luiz....@gmail.com, mar...@holtmann.org, net...@vger.kernel.org, pab...@redhat.com, syzkall...@googlegroups.com
Hello,

syzbot found the following issue on:

HEAD commit: ed23734c23d2 Merge tag 'net-6.4-rc1' of git://git.kernel.o..
git tree: net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=16b2a3f4280000
kernel config: https://syzkaller.appspot.com/x/.config?x=87f9126139666d37
dashboard link: https://syzkaller.appspot.com/bug?extid=cf54c1da6574b6c1b049
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/c43e1732e675/disk-ed23734c.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/8f4e7bce7a91/vmlinux-ed23734c.xz
kernel image: https://storage.googleapis.com/syzbot-assets/9fe83b099e40/bzImage-ed23734c.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+cf54c1...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: slab-use-after-free in instrument_atomic_read_write include/linux/instrumented.h:96 [inline]
BUG: KASAN: slab-use-after-free in atomic_dec_and_test include/linux/atomic/atomic-instrumented.h:575 [inline]
BUG: KASAN: slab-use-after-free in hci_conn_drop include/net/bluetooth/hci_core.h:1418 [inline]
BUG: KASAN: slab-use-after-free in sco_chan_del+0x102/0x4f0 net/bluetooth/sco.c:169
Write of size 4 at addr ffff88804dbea010 by task syz-executor.0/7018

CPU: 0 PID: 7018 Comm: syz-executor.0 Not tainted 6.3.0-syzkaller-13379-ged23734c23d2 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/14/2023
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xd9/0x150 lib/dump_stack.c:106
print_address_description.constprop.0+0x2c/0x3c0 mm/kasan/report.c:351
print_report mm/kasan/report.c:462 [inline]
kasan_report+0x11c/0x130 mm/kasan/report.c:572
check_region_inline mm/kasan/generic.c:181 [inline]
kasan_check_range+0x141/0x190 mm/kasan/generic.c:187
instrument_atomic_read_write include/linux/instrumented.h:96 [inline]
atomic_dec_and_test include/linux/atomic/atomic-instrumented.h:575 [inline]
hci_conn_drop include/net/bluetooth/hci_core.h:1418 [inline]
sco_chan_del+0x102/0x4f0 net/bluetooth/sco.c:169
__sco_sock_close+0x178/0x740 net/bluetooth/sco.c:454
sco_sock_close net/bluetooth/sco.c:469 [inline]
sco_sock_release+0x81/0x360 net/bluetooth/sco.c:1267
__sock_release+0xcd/0x290 net/socket.c:653
sock_close+0x1c/0x20 net/socket.c:1397
__fput+0x27c/0xa90 fs/file_table.c:321
task_work_run+0x16f/0x270 kernel/task_work.c:179
get_signal+0x1c7/0x25b0 kernel/signal.c:2650
arch_do_signal_or_restart+0x79/0x5c0 arch/x86/kernel/signal.c:306
exit_to_user_mode_loop kernel/entry/common.c:168 [inline]
exit_to_user_mode_prepare+0x11f/0x240 kernel/entry/common.c:204
__syscall_exit_to_user_mode_work kernel/entry/common.c:286 [inline]
syscall_exit_to_user_mode+0x1d/0x50 kernel/entry/common.c:297
do_syscall_64+0x46/0xb0 arch/x86/entry/common.c:86
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f7a97a8c169
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 f1 19 00 00 90 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f7a965fe168 EFLAGS: 00000246 ORIG_RAX: 000000000000002a
RAX: fffffffffffffffc RBX: 00007f7a97babf80 RCX: 00007f7a97a8c169
RDX: 0000000000000008 RSI: 0000000020002ec0 RDI: 0000000000000004
RBP: 00007f7a97ae7ca1 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffca219560f R14: 00007f7a965fe300 R15: 0000000000022000
</TASK>

Allocated by task 7018:
kasan_save_stack+0x22/0x40 mm/kasan/common.c:45
kasan_set_track+0x25/0x30 mm/kasan/common.c:52
____kasan_kmalloc mm/kasan/common.c:374 [inline]
____kasan_kmalloc mm/kasan/common.c:333 [inline]
__kasan_kmalloc+0xa2/0xb0 mm/kasan/common.c:383
kmalloc include/linux/slab.h:559 [inline]
kzalloc include/linux/slab.h:680 [inline]
hci_conn_add+0xb8/0x16b0 net/bluetooth/hci_conn.c:986
hci_connect_sco+0x3c7/0x1050 net/bluetooth/hci_conn.c:1663
sco_connect net/bluetooth/sco.c:264 [inline]
sco_sock_connect+0x2d7/0xae0 net/bluetooth/sco.c:610
__sys_connect_file+0x153/0x1a0 net/socket.c:2003
__sys_connect+0x165/0x1a0 net/socket.c:2020
__do_sys_connect net/socket.c:2030 [inline]
__se_sys_connect net/socket.c:2027 [inline]
__x64_sys_connect+0x73/0xb0 net/socket.c:2027
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

Freed by task 5708:
kasan_save_stack+0x22/0x40 mm/kasan/common.c:45
kasan_set_track+0x25/0x30 mm/kasan/common.c:52
kasan_save_free_info+0x2e/0x40 mm/kasan/generic.c:521
____kasan_slab_free mm/kasan/common.c:236 [inline]
____kasan_slab_free+0x160/0x1c0 mm/kasan/common.c:200
kasan_slab_free include/linux/kasan.h:162 [inline]
slab_free_hook mm/slub.c:1781 [inline]
slab_free_freelist_hook+0x8b/0x1c0 mm/slub.c:1807
slab_free mm/slub.c:3786 [inline]
__kmem_cache_free+0xaf/0x2d0 mm/slub.c:3799
device_release+0xa3/0x240 drivers/base/core.c:2484
kobject_cleanup lib/kobject.c:683 [inline]
kobject_release lib/kobject.c:714 [inline]
kref_put include/linux/kref.h:65 [inline]
kobject_put+0x1c2/0x4d0 lib/kobject.c:731
put_device+0x1f/0x30 drivers/base/core.c:3733
hci_conn_del+0x1e5/0x950 net/bluetooth/hci_conn.c:1162
hci_conn_unlink+0x2ce/0x460 net/bluetooth/hci_conn.c:1109
hci_conn_unlink+0x362/0x460 net/bluetooth/hci_conn.c:1087
hci_conn_hash_flush+0x19b/0x270 net/bluetooth/hci_conn.c:2479
hci_dev_close_sync+0x5fb/0x1200 net/bluetooth/hci_sync.c:4941
hci_dev_do_close+0x31/0x70 net/bluetooth/hci_core.c:554
hci_unregister_dev+0x1ce/0x580 net/bluetooth/hci_core.c:2703
vhci_release+0x80/0xf0 drivers/bluetooth/hci_vhci.c:669
__fput+0x27c/0xa90 fs/file_table.c:321
task_work_run+0x16f/0x270 kernel/task_work.c:179
exit_task_work include/linux/task_work.h:38 [inline]
do_exit+0xad3/0x2960 kernel/exit.c:871
do_group_exit+0xd4/0x2a0 kernel/exit.c:1021
__do_sys_exit_group kernel/exit.c:1032 [inline]
__se_sys_exit_group kernel/exit.c:1030 [inline]
__x64_sys_exit_group+0x3e/0x50 kernel/exit.c:1030
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

The buggy address belongs to the object at ffff88804dbea000
which belongs to the cache kmalloc-4k of size 4096
The buggy address is located 16 bytes inside of
freed 4096-byte region [ffff88804dbea000, ffff88804dbeb000)

The buggy address belongs to the physical page:
page:ffffea000136fa00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x4dbe8
head:ffffea000136fa00 order:3 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff00000010200 ffff888012442140 dead000000000100 dead000000000122
raw: 0000000000000000 0000000000040004 00000001ffffffff 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 0x1d20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 4456, tgid 4456 (udevd), ts 192360753903, free_ts 185030986834
set_page_owner include/linux/page_owner.h:31 [inline]
post_alloc_hook+0x2db/0x350 mm/page_alloc.c:1731
prep_new_page mm/page_alloc.c:1738 [inline]
get_page_from_freelist+0xf41/0x2c00 mm/page_alloc.c:3502
__alloc_pages+0x1cb/0x4a0 mm/page_alloc.c:4768
alloc_pages+0x1aa/0x270 mm/mempolicy.c:2279
alloc_slab_page mm/slub.c:1851 [inline]
allocate_slab+0x25f/0x390 mm/slub.c:1998
new_slab mm/slub.c:2051 [inline]
___slab_alloc+0xa91/0x1400 mm/slub.c:3192
__slab_alloc.constprop.0+0x56/0xa0 mm/slub.c:3291
__slab_alloc_node mm/slub.c:3344 [inline]
slab_alloc_node mm/slub.c:3441 [inline]
__kmem_cache_alloc_node+0x136/0x320 mm/slub.c:3490
kmalloc_trace+0x26/0xe0 mm/slab_common.c:1057
kmalloc include/linux/slab.h:559 [inline]
kzalloc include/linux/slab.h:680 [inline]
uevent_show+0x15d/0x380 drivers/base/core.c:2641
dev_attr_show+0x4f/0xd0 drivers/base/core.c:2349
sysfs_kf_seq_show+0x21d/0x430 fs/sysfs/file.c:59
seq_read_iter+0x4f9/0x12d0 fs/seq_file.c:230
kernfs_fop_read_iter+0x4ce/0x690 fs/kernfs/file.c:279
call_read_iter include/linux/fs.h:1862 [inline]
new_sync_read fs/read_write.c:389 [inline]
vfs_read+0x4b1/0x8a0 fs/read_write.c:470
ksys_read+0x12b/0x250 fs/read_write.c:613
page last free stack trace:
reset_page_owner include/linux/page_owner.h:24 [inline]
free_pages_prepare mm/page_alloc.c:1302 [inline]
free_unref_page_prepare+0x62e/0xcb0 mm/page_alloc.c:2564
free_unref_page+0x33/0x370 mm/page_alloc.c:2659
__unfreeze_partials+0x17c/0x1a0 mm/slub.c:2636
qlink_free mm/kasan/quarantine.c:166 [inline]
qlist_free_all+0x6a/0x170 mm/kasan/quarantine.c:185
kasan_quarantine_reduce+0x195/0x220 mm/kasan/quarantine.c:292
__kasan_slab_alloc+0x63/0x90 mm/kasan/common.c:305
kasan_slab_alloc include/linux/kasan.h:186 [inline]
slab_post_alloc_hook mm/slab.h:711 [inline]
slab_alloc_node mm/slub.c:3451 [inline]
__kmem_cache_alloc_node+0x17c/0x320 mm/slub.c:3490
kmalloc_trace+0x26/0xe0 mm/slab_common.c:1057
kmalloc include/linux/slab.h:559 [inline]
kzalloc include/linux/slab.h:680 [inline]
is_state_visited kernel/bpf/verifier.c:15459 [inline]
do_check kernel/bpf/verifier.c:15629 [inline]
do_check_common+0x2845/0xc620 kernel/bpf/verifier.c:18215
do_check_main kernel/bpf/verifier.c:18278 [inline]
bpf_check+0x74aa/0xb010 kernel/bpf/verifier.c:18899
bpf_prog_load+0x16d3/0x21f0 kernel/bpf/syscall.c:2648
__sys_bpf+0x149f/0x5420 kernel/bpf/syscall.c:5058
__do_sys_bpf kernel/bpf/syscall.c:5162 [inline]
__se_sys_bpf kernel/bpf/syscall.c:5160 [inline]
__x64_sys_bpf+0x79/0xc0 kernel/bpf/syscall.c:5160
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

Memory state around the buggy address:
ffff88804dbe9f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88804dbe9f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88804dbea000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88804dbea080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88804dbea100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
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If the bug is already fixed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want to change bug's subsystems, reply with:
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(See the list of subsystem names on the web dashboard)

If the bug is a duplicate of another bug, reply with:
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If you want to undo deduplication, reply with:
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Ruihan Li

unread,
May 15, 2023, 12:01:48 PM5/15/23
to linux-b...@vger.kernel.org, luiz....@gmail.com, johan....@gmail.com, mar...@holtmann.org, syzbot+cf54c1...@syzkaller.appspotmail.com, da...@davemloft.net, edum...@google.com, ku...@kernel.org, linux-...@vger.kernel.org, net...@vger.kernel.org, pab...@redhat.com, syzkall...@googlegroups.com, Ruihan Li
It seems that, while we remember to release unestablished SCO connections when
the ACL connection tears down (since [1]), we forget to call hci_connect_cfm
before hci_conn_del. Without hci_connect_cfm, the SCO socket may not be
notified to clean up its associated SCO connection (in sco_connect_cfm),
causing this use-after-free risk when operating the socket.

[1] https://lore.kernel.org/linux-bluetooth/20230203173024.1.Ieb6662276f3bd3d79e9134ab04523d584c300c45@changeid/

However, I cannot figure out an easy and clear way to pass a proper error code
to hci_connect_cfm at this point, so I wonder if it is acceptable to use
HCI_ERROR_UNSPECIFIED directly. That said, the patch will look like this:

diff --git a/net/bluetooth/hci_conn.c b/net/bluetooth/hci_conn.c
index f75ef12f1..73c120258 100644
--- a/net/bluetooth/hci_conn.c
+++ b/net/bluetooth/hci_conn.c
@@ -1102,8 +1102,10 @@ static void hci_conn_unlink(struct hci_conn *conn)
*/
if ((child->type == SCO_LINK ||
child->type == ESCO_LINK) &&
- child->handle == HCI_CONN_HANDLE_UNSET)
+ child->handle == HCI_CONN_HANDLE_UNSET) {
+ hci_connect_cfm(child, HCI_ERROR_UNSPECIFIED);
hci_conn_del(child);
+ }
}

return;

Also, while this fix can semantically be applied to v6.1 and above, an explicit
backport is required due to the hci_conn_unlink refactoring in the mainline.

Thanks,
Ruihan Li

syzbot

unread,
Aug 17, 2023, 8:56:55 AM8/17/23
to da...@davemloft.net, edum...@google.com, johan....@gmail.com, ku...@kernel.org, linux-b...@vger.kernel.org, linux-...@vger.kernel.org, lrh...@pku.edu.cn, luiz....@gmail.com, mar...@holtmann.org, net...@vger.kernel.org, pab...@redhat.com, syzkall...@googlegroups.com
syzbot has found a reproducer for the following issue on:

HEAD commit: 47762f086974 Add linux-next specific files for 20230817
git tree: linux-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=17899507a80000
kernel config: https://syzkaller.appspot.com/x/.config?x=ed03cf326b3ef94c
dashboard link: https://syzkaller.appspot.com/bug?extid=cf54c1da6574b6c1b049
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=1125bc65a80000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=14ce8f03a80000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/c6f2ea3b7d7d/disk-47762f08.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/cf652ce6b802/vmlinux-47762f08.xz
kernel image: https://storage.googleapis.com/syzbot-assets/5f329a7749b6/bzImage-47762f08.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+cf54c1...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: slab-use-after-free in instrument_atomic_read_write include/linux/instrumented.h:96 [inline]
BUG: KASAN: slab-use-after-free in atomic_dec_and_test include/linux/atomic/atomic-instrumented.h:1375 [inline]
BUG: KASAN: slab-use-after-free in hci_conn_drop include/net/bluetooth/hci_core.h:1497 [inline]
BUG: KASAN: slab-use-after-free in sco_chan_del+0x102/0x4f0 net/bluetooth/sco.c:171
Write of size 4 at addr ffff88807cee0010 by task syz-executor360/8962

CPU: 1 PID: 8962 Comm: syz-executor360 Not tainted 6.5.0-rc6-next-20230817-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/26/2023
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xd9/0x1b0 lib/dump_stack.c:106
print_address_description mm/kasan/report.c:364 [inline]
print_report+0xc4/0x620 mm/kasan/report.c:475
kasan_report+0xda/0x110 mm/kasan/report.c:588
check_region_inline mm/kasan/generic.c:181 [inline]
kasan_check_range+0xef/0x190 mm/kasan/generic.c:187
instrument_atomic_read_write include/linux/instrumented.h:96 [inline]
atomic_dec_and_test include/linux/atomic/atomic-instrumented.h:1375 [inline]
hci_conn_drop include/net/bluetooth/hci_core.h:1497 [inline]
sco_chan_del+0x102/0x4f0 net/bluetooth/sco.c:171
__sco_sock_close+0xf2/0x690 net/bluetooth/sco.c:454
sco_sock_close net/bluetooth/sco.c:469 [inline]
sco_sock_release+0x6f/0x2c0 net/bluetooth/sco.c:1246
__sock_release+0xae/0x260 net/socket.c:659
sock_close+0x1c/0x20 net/socket.c:1401
__fput+0x3f7/0xac0 fs/file_table.c:384
task_work_run+0x14d/0x240 kernel/task_work.c:179
exit_task_work include/linux/task_work.h:38 [inline]
do_exit+0xa99/0x2a20 kernel/exit.c:874
do_group_exit+0xd4/0x2a0 kernel/exit.c:1024
get_signal+0x23d1/0x27b0 kernel/signal.c:2892
arch_do_signal_or_restart+0x90/0x7f0 arch/x86/kernel/signal.c:309
exit_to_user_mode_loop kernel/entry/common.c:168 [inline]
exit_to_user_mode_prepare+0x11f/0x240 kernel/entry/common.c:204
__syscall_exit_to_user_mode_work kernel/entry/common.c:286 [inline]
syscall_exit_to_user_mode+0x1d/0x60 kernel/entry/common.c:297
do_syscall_64+0x44/0xb0 arch/x86/entry/common.c:86
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7ff68c148bb9
Code: Unable to access opcode bytes at 0x7ff68c148b8f.
RSP: 002b:00007ffe45e76968 EFLAGS: 00000246 ORIG_RAX: 000000000000002a
RAX: fffffffffffffffc RBX: 0000000000000003 RCX: 00007ff68c148bb9
RDX: 0000000000000008 RSI: 0000000020000040 RDI: 0000000000000004
RBP: 0000000000000003 R08: 00007ffe45e769a0 R09: 00007ffe45e769a0
R10: 0000000000000000 R11: 0000000000000246 R12: 0000555556df1370
R13: 0000000000000016 R14: 0000000000000251 R15: 431bde82d7b634db
</TASK>

Allocated by task 8762:
kasan_save_stack+0x33/0x50 mm/kasan/common.c:45
kasan_set_track+0x25/0x30 mm/kasan/common.c:52
____kasan_kmalloc mm/kasan/common.c:374 [inline]
__kasan_kmalloc+0xa2/0xb0 mm/kasan/common.c:383
kmalloc include/linux/slab.h:600 [inline]
kzalloc include/linux/slab.h:721 [inline]
hci_conn_add+0xc2/0x1770 net/bluetooth/hci_conn.c:952
hci_connect_sco+0x3ac/0xf80 net/bluetooth/hci_conn.c:1671
sco_connect net/bluetooth/sco.c:266 [inline]
sco_sock_connect+0x2c7/0xa50 net/bluetooth/sco.c:591
__sys_connect_file+0x15b/0x1a0 net/socket.c:2032
__sys_connect+0x145/0x170 net/socket.c:2049
__do_sys_connect net/socket.c:2059 [inline]
__se_sys_connect net/socket.c:2056 [inline]
__x64_sys_connect+0x72/0xb0 net/socket.c:2056
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

Freed by task 5061:
kasan_save_stack+0x33/0x50 mm/kasan/common.c:45
kasan_set_track+0x25/0x30 mm/kasan/common.c:52
kasan_save_free_info+0x2b/0x40 mm/kasan/generic.c:522
____kasan_slab_free mm/kasan/common.c:236 [inline]
____kasan_slab_free+0x15e/0x1b0 mm/kasan/common.c:200
kasan_slab_free include/linux/kasan.h:164 [inline]
slab_free_hook mm/slub.c:1800 [inline]
slab_free_freelist_hook+0x114/0x1e0 mm/slub.c:1826
slab_free mm/slub.c:3809 [inline]
__kmem_cache_free+0xb8/0x2f0 mm/slub.c:3822
device_release+0xa1/0x240 drivers/base/core.c:2484
kobject_cleanup lib/kobject.c:689 [inline]
kobject_release lib/kobject.c:720 [inline]
kref_put include/linux/kref.h:65 [inline]
kobject_put+0x1f7/0x5b0 lib/kobject.c:737
put_device+0x1f/0x30 drivers/base/core.c:3731
hci_conn_unlink+0x60a/0x840 net/bluetooth/hci_conn.c:1071
hci_conn_del+0x59/0xd10 net/bluetooth/hci_conn.c:1097
hci_abort_conn_sync+0x7fc/0xb70 net/bluetooth/hci_sync.c:5417
abort_conn_sync+0x18e/0x3a0 net/bluetooth/hci_conn.c:2869
hci_cmd_sync_work+0x1a4/0x3c0 net/bluetooth/hci_sync.c:306
process_one_work+0x887/0x15d0 kernel/workqueue.c:2630
process_scheduled_works kernel/workqueue.c:2703 [inline]
worker_thread+0x8bb/0x1290 kernel/workqueue.c:2784
kthread+0x33a/0x430 kernel/kthread.c:388
ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:304

Last potentially related work creation:
kasan_save_stack+0x33/0x50 mm/kasan/common.c:45
__kasan_record_aux_stack+0xbc/0xd0 mm/kasan/generic.c:492
insert_work+0x38/0x230 kernel/workqueue.c:1647
__queue_work+0x5d2/0x1060 kernel/workqueue.c:1799
__queue_delayed_work+0x1bf/0x260 kernel/workqueue.c:1950
queue_delayed_work_on+0x106/0x130 kernel/workqueue.c:1986
queue_delayed_work include/linux/workqueue.h:569 [inline]
hci_conn_drop include/net/bluetooth/hci_core.h:1523 [inline]
hci_conn_drop include/net/bluetooth/hci_core.h:1493 [inline]
sco_chan_del+0x1f8/0x4f0 net/bluetooth/sco.c:171
__sco_sock_close+0xf2/0x690 net/bluetooth/sco.c:454
sco_sock_close net/bluetooth/sco.c:469 [inline]
sco_sock_release+0x6f/0x2c0 net/bluetooth/sco.c:1246
__sock_release+0xae/0x260 net/socket.c:659
sock_close+0x1c/0x20 net/socket.c:1401
__fput+0x3f7/0xac0 fs/file_table.c:384
task_work_run+0x14d/0x240 kernel/task_work.c:179
exit_task_work include/linux/task_work.h:38 [inline]
do_exit+0xa99/0x2a20 kernel/exit.c:874
do_group_exit+0xd4/0x2a0 kernel/exit.c:1024
get_signal+0x23d1/0x27b0 kernel/signal.c:2892
arch_do_signal_or_restart+0x90/0x7f0 arch/x86/kernel/signal.c:309
exit_to_user_mode_loop kernel/entry/common.c:168 [inline]
exit_to_user_mode_prepare+0x11f/0x240 kernel/entry/common.c:204
__syscall_exit_to_user_mode_work kernel/entry/common.c:286 [inline]
syscall_exit_to_user_mode+0x1d/0x60 kernel/entry/common.c:297
do_syscall_64+0x44/0xb0 arch/x86/entry/common.c:86
entry_SYSCALL_64_after_hwframe+0x63/0xcd

The buggy address belongs to the object at ffff88807cee0000
which belongs to the cache kmalloc-4k of size 4096
The buggy address is located 16 bytes inside of
freed 4096-byte region [ffff88807cee0000, ffff88807cee1000)

The buggy address belongs to the physical page:
page:ffffea0001f3b800 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x7cee0
head:ffffea0001f3b800 order:3 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff00000010200 ffff888012c42140 ffffea00009e7000 dead000000000002
raw: 0000000000000000 0000000000040004 00000001ffffffff 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 0xd2040(__GFP_IO|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5046, tgid 5046 (syz-executor360), ts 144073960140, free_ts 83497589835
set_page_owner include/linux/page_owner.h:31 [inline]
post_alloc_hook+0x2d2/0x350 mm/page_alloc.c:1550
prep_new_page mm/page_alloc.c:1557 [inline]
get_page_from_freelist+0x10d7/0x31b0 mm/page_alloc.c:3233
__alloc_pages+0x1d0/0x4a0 mm/page_alloc.c:4489
alloc_pages+0x1a9/0x270 mm/mempolicy.c:2298
alloc_slab_page mm/slub.c:1870 [inline]
allocate_slab+0x24e/0x380 mm/slub.c:2017
new_slab mm/slub.c:2070 [inline]
___slab_alloc+0x8bc/0x1570 mm/slub.c:3223
__slab_alloc.constprop.0+0x56/0xa0 mm/slub.c:3322
__slab_alloc_node mm/slub.c:3375 [inline]
slab_alloc_node mm/slub.c:3468 [inline]
__kmem_cache_alloc_node+0x137/0x350 mm/slub.c:3517
__do_kmalloc_node mm/slab_common.c:1003 [inline]
__kmalloc+0x4f/0x100 mm/slab_common.c:1017
kmalloc include/linux/slab.h:604 [inline]
tomoyo_realpath_from_path+0xb9/0x710 security/tomoyo/realpath.c:251
tomoyo_get_realpath security/tomoyo/file.c:151 [inline]
tomoyo_path_perm+0x271/0x450 security/tomoyo/file.c:822
security_inode_getattr+0xf1/0x150 security/security.c:2153
vfs_getattr fs/stat.c:206 [inline]
vfs_statx+0x180/0x430 fs/stat.c:281
vfs_fstatat+0x90/0xb0 fs/stat.c:315
__do_sys_newfstatat+0x98/0x110 fs/stat.c:485
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80
page last free stack trace:
reset_page_owner include/linux/page_owner.h:24 [inline]
free_pages_prepare mm/page_alloc.c:1150 [inline]
free_unref_page_prepare+0x479/0xa50 mm/page_alloc.c:2362
free_unref_page+0x33/0x3b0 mm/page_alloc.c:2455
__unfreeze_partials+0x21d/0x240 mm/slub.c:2655
qlink_free mm/kasan/quarantine.c:166 [inline]
qlist_free_all+0x6a/0x170 mm/kasan/quarantine.c:185
kasan_quarantine_reduce+0x18b/0x1d0 mm/kasan/quarantine.c:292
__kasan_slab_alloc+0x65/0x90 mm/kasan/common.c:305
kasan_slab_alloc include/linux/kasan.h:188 [inline]
slab_post_alloc_hook mm/slab.h:762 [inline]
slab_alloc_node mm/slub.c:3478 [inline]
kmem_cache_alloc_node+0x185/0x3f0 mm/slub.c:3523
__alloc_skb+0x287/0x330 net/core/skbuff.c:634
alloc_skb_fclone include/linux/skbuff.h:1336 [inline]
tcp_stream_alloc_skb+0x34/0x560 net/ipv4/tcp.c:869
tcp_sendmsg_locked+0xea5/0x3430 net/ipv4/tcp.c:1150
tcp_sendmsg+0x2e/0x40 net/ipv4/tcp.c:1336
inet_sendmsg+0x9d/0xe0 net/ipv4/af_inet.c:840
sock_sendmsg_nosec net/socket.c:730 [inline]
sock_sendmsg+0xd9/0x180 net/socket.c:753
sock_write_iter+0x29b/0x3d0 net/socket.c:1140
call_write_iter include/linux/fs.h:1983 [inline]
new_sync_write fs/read_write.c:491 [inline]
vfs_write+0x650/0xe40 fs/read_write.c:584
ksys_write+0x1f0/0x250 fs/read_write.c:637

Memory state around the buggy address:
ffff88807cedff00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88807cedff80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88807cee0000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88807cee0080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88807cee0100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

syzbot

unread,
Aug 18, 2023, 12:39:37 AM8/18/23
to da...@davemloft.net, edum...@google.com, johan....@gmail.com, ku...@kernel.org, linux-b...@vger.kernel.org, linux-...@vger.kernel.org, lrh...@pku.edu.cn, luiz....@gmail.com, luiz.vo...@intel.com, mar...@holtmann.org, net...@vger.kernel.org, pab...@redhat.com, p...@iki.fi, syzkall...@googlegroups.com
syzbot has bisected this issue to:

commit 45c37c4e9c9aab5bb1cf5778d8e5ebd9f9ad820a
Author: Luiz Augusto von Dentz <luiz.vo...@intel.com>
Date: Wed Aug 9 23:49:33 2023 +0000

Bluetooth: hci_sync: Fix UAF in hci_disconnect_all_sync

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=1331e265a80000
start commit: 47762f086974 Add linux-next specific files for 20230817
git tree: linux-next
final oops: https://syzkaller.appspot.com/x/report.txt?x=10b1e265a80000
console output: https://syzkaller.appspot.com/x/log.txt?x=1731e265a80000
Reported-by: syzbot+cf54c1...@syzkaller.appspotmail.com
Fixes: 45c37c4e9c9a ("Bluetooth: hci_sync: Fix UAF in hci_disconnect_all_sync")

For information about bisection process see: https://goo.gl/tpsmEJ#bisection

Hillf Danton

unread,
Aug 18, 2023, 7:48:58 AM8/18/23
to syzbot, linux-...@vger.kernel.org, syzkall...@googlegroups.com
On Thu, 17 Aug 2023 05:56:53 -0700
> HEAD commit: 47762f086974 Add linux-next specific files for 20230817
> git tree: linux-next
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=14ce8f03a80000

Reset conn->hcon before freeing hcon to avoid double free.

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git 47762f086974

--- x/net/bluetooth/sco.c
+++ y/net/bluetooth/sco.c
@@ -155,6 +155,7 @@ static struct sco_conn *sco_conn_add(str
* Must be called on the locked socket. */
static void sco_chan_del(struct sock *sk, int err)
{
+ struct hci_conn *hcon;
struct sco_conn *conn;

conn = sco_pi(sk)->conn;
@@ -165,10 +166,12 @@ static void sco_chan_del(struct sock *sk
sco_conn_lock(conn);
conn->sk = NULL;
sco_pi(sk)->conn = NULL;
+ hcon = conn->hcon;
+ conn->hcon = NULL;
sco_conn_unlock(conn);

- if (conn->hcon)
- hci_conn_drop(conn->hcon);
+ if (hcon)
+ hci_conn_drop(hcon);
}

sk->sk_state = BT_CLOSED;
--

syzbot

unread,
Aug 18, 2023, 10:05:28 AM8/18/23
to hda...@sina.com, linux-...@vger.kernel.org, syzkall...@googlegroups.com
Hello,

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

==================================================================
BUG: KASAN: slab-use-after-free in instrument_atomic_read_write include/linux/instrumented.h:96 [inline]
BUG: KASAN: slab-use-after-free in atomic_dec_and_test include/linux/atomic/atomic-instrumented.h:1375 [inline]
BUG: KASAN: slab-use-after-free in hci_conn_drop include/net/bluetooth/hci_core.h:1497 [inline]
BUG: KASAN: slab-use-after-free in sco_chan_del+0x10a/0x500 net/bluetooth/sco.c:174
Write of size 4 at addr ffff88806abb0010 by task syz-executor.4/9743

CPU: 0 PID: 9743 Comm: syz-executor.4 Not tainted 6.5.0-rc6-next-20230817-syzkaller-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/26/2023
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xd9/0x1b0 lib/dump_stack.c:106
print_address_description mm/kasan/report.c:364 [inline]
print_report+0xc4/0x620 mm/kasan/report.c:475
kasan_report+0xda/0x110 mm/kasan/report.c:588
check_region_inline mm/kasan/generic.c:181 [inline]
kasan_check_range+0xef/0x190 mm/kasan/generic.c:187
instrument_atomic_read_write include/linux/instrumented.h:96 [inline]
atomic_dec_and_test include/linux/atomic/atomic-instrumented.h:1375 [inline]
hci_conn_drop include/net/bluetooth/hci_core.h:1497 [inline]
sco_chan_del+0x10a/0x500 net/bluetooth/sco.c:174
__sco_sock_close+0xf2/0x690 net/bluetooth/sco.c:457
sco_sock_close net/bluetooth/sco.c:472 [inline]
sco_sock_release+0x6f/0x2c0 net/bluetooth/sco.c:1249
__sock_release+0xae/0x260 net/socket.c:659
sock_close+0x1c/0x20 net/socket.c:1401
__fput+0x3f7/0xac0 fs/file_table.c:384
task_work_run+0x14d/0x240 kernel/task_work.c:179
get_signal+0x106f/0x27b0 kernel/signal.c:2668
arch_do_signal_or_restart+0x90/0x7f0 arch/x86/kernel/signal.c:309
exit_to_user_mode_loop kernel/entry/common.c:168 [inline]
exit_to_user_mode_prepare+0x11f/0x240 kernel/entry/common.c:204
__syscall_exit_to_user_mode_work kernel/entry/common.c:286 [inline]
syscall_exit_to_user_mode+0x1d/0x60 kernel/entry/common.c:297
do_syscall_64+0x44/0xb0 arch/x86/entry/common.c:86
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f851807cae9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 20 00 00 90 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 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f8518e2d0c8 EFLAGS: 00000246 ORIG_RAX: 000000000000002a
RAX: fffffffffffffffc RBX: 00007f851819bf80 RCX: 00007f851807cae9
RDX: 0000000000000008 RSI: 0000000020000040 RDI: 0000000000000004
RBP: 00007f85180c847a R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000000b R14: 00007f851819bf80 R15: 00007fff1d126688
</TASK>

Allocated by task 9661:
kasan_save_stack+0x33/0x50 mm/kasan/common.c:45
kasan_set_track+0x25/0x30 mm/kasan/common.c:52
____kasan_kmalloc mm/kasan/common.c:374 [inline]
__kasan_kmalloc+0xa2/0xb0 mm/kasan/common.c:383
kmalloc include/linux/slab.h:600 [inline]
kzalloc include/linux/slab.h:721 [inline]
hci_conn_add+0xc2/0x1770 net/bluetooth/hci_conn.c:952
hci_connect_sco+0x3ac/0xf80 net/bluetooth/hci_conn.c:1671
sco_connect net/bluetooth/sco.c:269 [inline]
sco_sock_connect+0x2c7/0xa50 net/bluetooth/sco.c:594
__sys_connect_file+0x15b/0x1a0 net/socket.c:2032
__sys_connect+0x145/0x170 net/socket.c:2049
__do_sys_connect net/socket.c:2059 [inline]
__se_sys_connect net/socket.c:2056 [inline]
__x64_sys_connect+0x72/0xb0 net/socket.c:2056
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

Freed by task 5407:
sco_chan_del+0x1ff/0x500 net/bluetooth/sco.c:174
__sco_sock_close+0xf2/0x690 net/bluetooth/sco.c:457
sco_sock_close net/bluetooth/sco.c:472 [inline]
sco_sock_release+0x6f/0x2c0 net/bluetooth/sco.c:1249
__sock_release+0xae/0x260 net/socket.c:659
sock_close+0x1c/0x20 net/socket.c:1401
__fput+0x3f7/0xac0 fs/file_table.c:384
task_work_run+0x14d/0x240 kernel/task_work.c:179
get_signal+0x106f/0x27b0 kernel/signal.c:2668
arch_do_signal_or_restart+0x90/0x7f0 arch/x86/kernel/signal.c:309
exit_to_user_mode_loop kernel/entry/common.c:168 [inline]
exit_to_user_mode_prepare+0x11f/0x240 kernel/entry/common.c:204
__syscall_exit_to_user_mode_work kernel/entry/common.c:286 [inline]
syscall_exit_to_user_mode+0x1d/0x60 kernel/entry/common.c:297
do_syscall_64+0x44/0xb0 arch/x86/entry/common.c:86
entry_SYSCALL_64_after_hwframe+0x63/0xcd

The buggy address belongs to the object at ffff88806abb0000
which belongs to the cache kmalloc-4k of size 4096
The buggy address is located 16 bytes inside of
freed 4096-byte region [ffff88806abb0000, ffff88806abb1000)

The buggy address belongs to the physical page:
page:ffffea0001aaec00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x6abb0
head:ffffea0001aaec00 order:3 entire_mapcount:0 nr_pages_mapped:0 pincount:0
anon flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff00000010200 ffff888012c42140 0000000000000000 dead000000000001
raw: 0000000000000000 0000000000040004 00000001ffffffff 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 0x1d2040(__GFP_IO|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 5425, tgid 5425 (udevd), ts 183359251571, free_ts 183195743543
slab_alloc mm/slub.c:3486 [inline]
__kmem_cache_alloc_lru mm/slub.c:3493 [inline]
kmem_cache_alloc+0x172/0x3b0 mm/slub.c:3502
getname_flags.part.0+0x50/0x4d0 fs/namei.c:140
getname_flags+0x9c/0xf0 include/linux/audit.h:319
vfs_fstatat+0x77/0xb0 fs/stat.c:314
__do_sys_newfstatat+0x98/0x110 fs/stat.c:485
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

Memory state around the buggy address:
ffff88806abaff00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88806abaff80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88806abb0000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88806abb0080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88806abb0100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


Tested on:

commit: 47762f08 Add linux-next specific files for 20230817
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
console output: https://syzkaller.appspot.com/x/log.txt?x=16a0da65a80000
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=1730dba0680000

syzbot

unread,
Aug 18, 2023, 3:24:58 PM8/18/23
to p...@iki.fi, p...@iki.fi, syzkall...@googlegroups.com
> #syz test git://git.kernel.org/pub/scm/linux/kernel/git/bluetooth/bluetooth-next.git f0835e7404b7f6fd825fc1ad7a174253a54234cf

Your commands are accepted, but please keep syzkall...@googlegroups.com mailing list in CC next time. It serves as a history of what happened with each bug report. Thank you.

>
> --- a/net/bluetooth/hci_conn.c
> +++ b/net/bluetooth/hci_conn.c
> @@ -1072,8 +1072,14 @@ static void hci_conn_unlink(struct hci_conn *conn)
> */
> if ((child->type == SCO_LINK ||
> child->type == ESCO_LINK) &&
> - HCI_CONN_HANDLE_UNSET(child->handle))
> - hci_conn_del(child);
> + HCI_CONN_HANDLE_UNSET(child->handle)) {
> + u8 reason = conn->abort_reason;
> +
> + if (!reason)
> + reason = HCI_ERROR_REMOTE_USER_TERM;
> +
> + hci_conn_failed(child, reason);
> + }
> }
>
> return;
> --
> 2.41.0
>

syzbot

unread,
Aug 18, 2023, 4:04:36 PM8/18/23
to p...@iki.fi, syzkall...@googlegroups.com
Hello,

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

Reported-and-tested-by: syzbot+cf54c1...@syzkaller.appspotmail.com

Tested on:

commit: f0835e74 Bluetooth: ISO: Use defer setup to separate P..
git tree: git://git.kernel.org/pub/scm/linux/kernel/git/bluetooth/bluetooth-next.git
console output: https://syzkaller.appspot.com/x/log.txt?x=17f27eefa80000
kernel config: https://syzkaller.appspot.com/x/.config?x=4b3a4035b595be0
dashboard link: https://syzkaller.appspot.com/bug?extid=cf54c1da6574b6c1b049
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=142dbe4ba80000

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

Hillf Danton

unread,
Aug 18, 2023, 9:46:45 PM8/18/23
to syzbot, linux-...@vger.kernel.org, syzkall...@googlegroups.com
On Thu, 17 Aug 2023 05:56:53 -0700
> HEAD commit: 47762f086974 Add linux-next specific files for 20230817
> git tree: linux-next
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=14ce8f03a80000

Reset conn->hcon before freeing hcon to avoid double free.

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git 47762f086974

--- x/net/bluetooth/sco.c
+++ y/net/bluetooth/sco.c
@@ -155,6 +155,7 @@ static struct sco_conn *sco_conn_add(str
* Must be called on the locked socket. */
static void sco_chan_del(struct sock *sk, int err)
{
+ struct hci_conn *hcon;
struct sco_conn *conn;

conn = sco_pi(sk)->conn;
@@ -165,10 +166,12 @@ static void sco_chan_del(struct sock *sk
sco_conn_lock(conn);
conn->sk = NULL;
sco_pi(sk)->conn = NULL;
+ hcon = conn->hcon;
+ conn->hcon = NULL;
sco_conn_unlock(conn);

- if (conn->hcon)
- hci_conn_drop(conn->hcon);
+ if (hcon)
+ hci_conn_drop(hcon);
}

sk->sk_state = BT_CLOSED;
--- x/net/bluetooth/hci_conn.c
+++ y/net/bluetooth/hci_conn.c
@@ -618,16 +618,6 @@ static void hci_conn_timeout(struct work

WARN_ON(refcnt < 0);

- /* FIXME: It was observed that in pairing failed scenario, refcnt
- * drops below 0. Probably this is because l2cap_conn_del calls
- * l2cap_chan_del for each channel, and inside l2cap_chan_del conn is
- * dropped. After that loop hci_chan_del is called which also drops
- * conn. For now make sure that ACL is alive if refcnt is higher then 0,
- * otherwise drop it.
- */
- if (refcnt > 0)
- return;
-
hci_abort_conn(conn, hci_proto_disconn_ind(conn));
}

@@ -1019,7 +1009,7 @@ struct hci_conn *hci_conn_add(struct hci
INIT_DELAYED_WORK(&conn->idle_work, hci_conn_idle);
INIT_DELAYED_WORK(&conn->le_conn_timeout, le_conn_timeout);

- atomic_set(&conn->refcnt, 0);
+ atomic_set(&conn->refcnt, 1);

hci_dev_hold(hdev);

--

syzbot

unread,
Aug 18, 2023, 10:10:34 PM8/18/23
to hda...@sina.com, linux-...@vger.kernel.org, syzkall...@googlegroups.com
Hello,

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

Reported-and-tested-by: syzbot+cf54c1...@syzkaller.appspotmail.com

Tested on:

commit: 47762f08 Add linux-next specific files for 20230817
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
console output: https://syzkaller.appspot.com/x/log.txt?x=1738036fa80000
kernel config: https://syzkaller.appspot.com/x/.config?x=ed03cf326b3ef94c
dashboard link: https://syzkaller.appspot.com/bug?extid=cf54c1da6574b6c1b049
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=1400439ba80000

syzbot

unread,
Aug 19, 2023, 10:01:27 AM8/19/23
to linux-b...@vger.kernel.org, p...@iki.fi, syzkall...@googlegroups.com
Hello,

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

Reported-and-tested-by: syzbot+cf54c1...@syzkaller.appspotmail.com

Tested on:

commit: f0835e74 Bluetooth: ISO: Use defer setup to separate P..
git tree: git://git.kernel.org/pub/scm/linux/kernel/git/bluetooth/bluetooth-next.git
console output: https://syzkaller.appspot.com/x/log.txt?x=1479e265a80000
kernel config: https://syzkaller.appspot.com/x/.config?x=4b3a4035b595be0
dashboard link: https://syzkaller.appspot.com/bug?extid=cf54c1da6574b6c1b049
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=13b9e265a80000
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