[v6.6] KASAN: slab-use-after-free Read in hci_cmd_timeout
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syzbot
May 21, 2026, 9:13:34 AM (5 days ago) May 21
to syzkaller...@googlegroups.com
Hello,
syzbot found the following issue on:
HEAD commit: eac8889a3a1c Linux 6.6.140
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1514fa73980000
kernel config: https://syzkaller.appspot.com/x/.config?x=c5b35c4db8465904
dashboard link: https://syzkaller.appspot.com/bug?extid=634ac5df6d1363cb70da
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
Unfortunately, I don't have any reproducer for this issue yet.
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/284081ee4b1a/disk-eac8889a.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/6503c72409ee/vmlinux-eac8889a.xz
kernel image: https://storage.googleapis.com/syzbot-assets/5e529dbebdcb/bzImage-eac8889a.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+634ac5...@syzkaller.appspotmail.com
==================================================================
BUG: KASAN: slab-use-after-free in hci_cmd_timeout+0x1d0/0x1e0 net/bluetooth/hci_core.c:1463
Read of size 2 at addr ffff888026b29df8 by task kworker/u5:5/5781
CPU: 1 PID: 5781 Comm: kworker/u5:5 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Workqueue: hci2 hci_cmd_timeout
Call Trace:
<TASK>
dump_stack_lvl+0x18c/0x250 lib/dump_stack.c:106
print_address_description mm/kasan/report.c:364 [inline]
print_report+0xa8/0x210 mm/kasan/report.c:468
kasan_report+0x117/0x150 mm/kasan/report.c:581
hci_cmd_timeout+0x1d0/0x1e0 net/bluetooth/hci_core.c:1463
process_one_work kernel/workqueue.c:2653 [inline]
process_scheduled_works+0xa5d/0x15d0 kernel/workqueue.c:2730
worker_thread+0xa55/0xfc0 kernel/workqueue.c:2811
kthread+0x2fa/0x390 kernel/kthread.c:388
ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
</TASK>
Allocated by task 5781:
kasan_save_stack mm/kasan/common.c:46 [inline]
kasan_set_track+0x4e/0x70 mm/kasan/common.c:53
__kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:329
kasan_slab_alloc include/linux/kasan.h:188 [inline]
slab_post_alloc_hook+0x6e/0x4b0 mm/slab.h:767
slab_alloc_node mm/slub.c:3495 [inline]
slab_alloc mm/slub.c:3503 [inline]
__kmem_cache_alloc_lru mm/slub.c:3510 [inline]
kmem_cache_alloc+0x11a/0x2d0 mm/slub.c:3519
skb_clone+0x1eb/0x370 net/core/skbuff.c:1912
hci_send_cmd_sync net/bluetooth/hci_core.c:4067 [inline]
hci_cmd_work+0x283/0x650 net/bluetooth/hci_core.c:4087
process_one_work kernel/workqueue.c:2653 [inline]
process_scheduled_works+0xa5d/0x15d0 kernel/workqueue.c:2730
worker_thread+0xa55/0xfc0 kernel/workqueue.c:2811
kthread+0x2fa/0x390 kernel/kthread.c:388
ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
Freed by task 6860:
kasan_save_stack mm/kasan/common.c:46 [inline]
kasan_set_track+0x4e/0x70 mm/kasan/common.c:53
kasan_save_free_info+0x2e/0x50 mm/kasan/generic.c:522
____kasan_slab_free+0x126/0x1e0 mm/kasan/common.c:237
kasan_slab_free include/linux/kasan.h:164 [inline]
slab_free_hook mm/slub.c:1811 [inline]
slab_free_freelist_hook+0x130/0x1a0 mm/slub.c:1837
slab_free mm/slub.c:3830 [inline]
kmem_cache_free+0xf8/0x270 mm/slub.c:3852
kfree_skb include/linux/skbuff.h:1264 [inline]
__hci_req_sync+0x613/0x910 net/bluetooth/hci_request.c:184
hci_req_sync+0xa2/0xc0 net/bluetooth/hci_request.c:206
hci_inquiry+0x38f/0x600 net/bluetooth/hci_core.c:394
sock_do_ioctl+0xfc/0x310 net/socket.c:1219
sock_ioctl+0x5ba/0x7e0 net/socket.c:1340
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:871 [inline]
__se_sys_ioctl+0xfd/0x170 fs/ioctl.c:857
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
The buggy address belongs to the object at ffff888026b29dc0
which belongs to the cache skbuff_head_cache of size 240
The buggy address is located 56 bytes inside of
freed 240-byte region [ffff888026b29dc0, ffff888026b29eb0)
The buggy address belongs to the physical page:
page:ffffea00009aca40 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x26b29
flags: 0xfff00000000800(slab|node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff00000000800 ffff88801ea70640 ffffea000061a240 dead000000000004
raw: 0000000000000000 00000000000c000c 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x12cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY), pid 5139, tgid 5139 (udevadm), ts 34473257981, free_ts 34398408585
set_page_owner include/linux/page_owner.h:31 [inline]
post_alloc_hook+0x1c1/0x200 mm/page_alloc.c:1581
prep_new_page mm/page_alloc.c:1588 [inline]
get_page_from_freelist+0x1951/0x19e0 mm/page_alloc.c:3220
__alloc_pages+0x1f0/0x460 mm/page_alloc.c:4500
alloc_slab_page+0x5d/0x160 mm/slub.c:1881
allocate_slab mm/slub.c:2028 [inline]
new_slab+0x87/0x2d0 mm/slub.c:2081
___slab_alloc+0xc5d/0x12f0 mm/slub.c:3253
__slab_alloc mm/slub.c:3339 [inline]
__slab_alloc_node mm/slub.c:3392 [inline]
slab_alloc_node mm/slub.c:3485 [inline]
slab_alloc mm/slub.c:3503 [inline]
__kmem_cache_alloc_lru mm/slub.c:3510 [inline]
kmem_cache_alloc+0x1b3/0x2d0 mm/slub.c:3519
skb_clone+0x1eb/0x370 net/core/skbuff.c:1912
do_one_broadcast net/netlink/af_netlink.c:1457 [inline]
netlink_broadcast_filtered+0x658/0x1110 net/netlink/af_netlink.c:1536
netlink_broadcast+0x37/0x50 net/netlink/af_netlink.c:1560
uevent_net_broadcast_untagged lib/kobject_uevent.c:331 [inline]
kobject_uevent_net_broadcast+0x364/0x530 lib/kobject_uevent.c:409
kobject_uevent_env+0x550/0x8b0 lib/kobject_uevent.c:608
kobject_synth_uevent+0x582/0xbc0 lib/kobject_uevent.c:208
uevent_store+0x4c/0x70 drivers/base/bus.c:635
kernfs_fop_write_iter+0x3b6/0x520 fs/kernfs/file.c:352
call_write_iter include/linux/fs.h:2018 [inline]
new_sync_write fs/read_write.c:491 [inline]
vfs_write+0x46c/0x990 fs/read_write.c:584
page last free stack trace:
reset_page_owner include/linux/page_owner.h:24 [inline]
free_pages_prepare mm/page_alloc.c:1181 [inline]
free_unref_page_prepare+0x7b2/0x8c0 mm/page_alloc.c:2365
free_unref_page+0x32/0x2e0 mm/page_alloc.c:2458
discard_slab mm/slub.c:2127 [inline]
__unfreeze_partials+0x1cf/0x210 mm/slub.c:2667
put_cpu_partial+0x17c/0x250 mm/slub.c:2743
__slab_free+0x319/0x400 mm/slub.c:3700
qlink_free mm/kasan/quarantine.c:166 [inline]
qlist_free_all+0x75/0xd0 mm/kasan/quarantine.c:185
kasan_quarantine_reduce+0x143/0x160 mm/kasan/quarantine.c:292
__kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:306
kasan_slab_alloc include/linux/kasan.h:188 [inline]
slab_post_alloc_hook+0x6e/0x4b0 mm/slab.h:767
slab_alloc_node mm/slub.c:3495 [inline]
__kmem_cache_alloc_node+0x13a/0x250 mm/slub.c:3534
kmalloc_trace+0x2a/0xe0 mm/slab_common.c:1098
kmalloc include/linux/slab.h:600 [inline]
kzalloc include/linux/slab.h:721 [inline]
kernfs_fop_open+0x3f5/0xcc0 fs/kernfs/file.c:690
do_dentry_open+0x8c6/0x1500 fs/open.c:929
do_open fs/namei.c:3640 [inline]
path_openat+0x27f1/0x3230 fs/namei.c:3797
do_filp_open+0x1f5/0x430 fs/namei.c:3824
do_sys_openat2+0x134/0x1d0 fs/open.c:1421
Memory state around the buggy address:
ffff888026b29c80: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888026b29d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fc fc
>ffff888026b29d80: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb
^
ffff888026b29e00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888026b29e80: fb fb fb fb fb fb fc fc fc fc fc fc fc fc fc fc
==================================================================
---
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:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title
If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)
If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report
If you want to undo deduplication, reply with:
#syz undup
syzbot found the following issue on:
HEAD commit: eac8889a3a1c Linux 6.6.140
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1514fa73980000
kernel config: https://syzkaller.appspot.com/x/.config?x=c5b35c4db8465904
dashboard link: https://syzkaller.appspot.com/bug?extid=634ac5df6d1363cb70da
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
Unfortunately, I don't have any reproducer for this issue yet.
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/284081ee4b1a/disk-eac8889a.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/6503c72409ee/vmlinux-eac8889a.xz
kernel image: https://storage.googleapis.com/syzbot-assets/5e529dbebdcb/bzImage-eac8889a.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+634ac5...@syzkaller.appspotmail.com
==================================================================
BUG: KASAN: slab-use-after-free in hci_cmd_timeout+0x1d0/0x1e0 net/bluetooth/hci_core.c:1463
Read of size 2 at addr ffff888026b29df8 by task kworker/u5:5/5781
CPU: 1 PID: 5781 Comm: kworker/u5:5 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Workqueue: hci2 hci_cmd_timeout
Call Trace:
<TASK>
dump_stack_lvl+0x18c/0x250 lib/dump_stack.c:106
print_address_description mm/kasan/report.c:364 [inline]
print_report+0xa8/0x210 mm/kasan/report.c:468
kasan_report+0x117/0x150 mm/kasan/report.c:581
hci_cmd_timeout+0x1d0/0x1e0 net/bluetooth/hci_core.c:1463
process_one_work kernel/workqueue.c:2653 [inline]
process_scheduled_works+0xa5d/0x15d0 kernel/workqueue.c:2730
worker_thread+0xa55/0xfc0 kernel/workqueue.c:2811
kthread+0x2fa/0x390 kernel/kthread.c:388
ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
</TASK>
Allocated by task 5781:
kasan_save_stack mm/kasan/common.c:46 [inline]
kasan_set_track+0x4e/0x70 mm/kasan/common.c:53
__kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:329
kasan_slab_alloc include/linux/kasan.h:188 [inline]
slab_post_alloc_hook+0x6e/0x4b0 mm/slab.h:767
slab_alloc_node mm/slub.c:3495 [inline]
slab_alloc mm/slub.c:3503 [inline]
__kmem_cache_alloc_lru mm/slub.c:3510 [inline]
kmem_cache_alloc+0x11a/0x2d0 mm/slub.c:3519
skb_clone+0x1eb/0x370 net/core/skbuff.c:1912
hci_send_cmd_sync net/bluetooth/hci_core.c:4067 [inline]
hci_cmd_work+0x283/0x650 net/bluetooth/hci_core.c:4087
process_one_work kernel/workqueue.c:2653 [inline]
process_scheduled_works+0xa5d/0x15d0 kernel/workqueue.c:2730
worker_thread+0xa55/0xfc0 kernel/workqueue.c:2811
kthread+0x2fa/0x390 kernel/kthread.c:388
ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
Freed by task 6860:
kasan_save_stack mm/kasan/common.c:46 [inline]
kasan_set_track+0x4e/0x70 mm/kasan/common.c:53
kasan_save_free_info+0x2e/0x50 mm/kasan/generic.c:522
____kasan_slab_free+0x126/0x1e0 mm/kasan/common.c:237
kasan_slab_free include/linux/kasan.h:164 [inline]
slab_free_hook mm/slub.c:1811 [inline]
slab_free_freelist_hook+0x130/0x1a0 mm/slub.c:1837
slab_free mm/slub.c:3830 [inline]
kmem_cache_free+0xf8/0x270 mm/slub.c:3852
kfree_skb include/linux/skbuff.h:1264 [inline]
__hci_req_sync+0x613/0x910 net/bluetooth/hci_request.c:184
hci_req_sync+0xa2/0xc0 net/bluetooth/hci_request.c:206
hci_inquiry+0x38f/0x600 net/bluetooth/hci_core.c:394
sock_do_ioctl+0xfc/0x310 net/socket.c:1219
sock_ioctl+0x5ba/0x7e0 net/socket.c:1340
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:871 [inline]
__se_sys_ioctl+0xfd/0x170 fs/ioctl.c:857
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
The buggy address belongs to the object at ffff888026b29dc0
which belongs to the cache skbuff_head_cache of size 240
The buggy address is located 56 bytes inside of
freed 240-byte region [ffff888026b29dc0, ffff888026b29eb0)
The buggy address belongs to the physical page:
page:ffffea00009aca40 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x26b29
flags: 0xfff00000000800(slab|node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff00000000800 ffff88801ea70640 ffffea000061a240 dead000000000004
raw: 0000000000000000 00000000000c000c 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x12cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY), pid 5139, tgid 5139 (udevadm), ts 34473257981, free_ts 34398408585
set_page_owner include/linux/page_owner.h:31 [inline]
post_alloc_hook+0x1c1/0x200 mm/page_alloc.c:1581
prep_new_page mm/page_alloc.c:1588 [inline]
get_page_from_freelist+0x1951/0x19e0 mm/page_alloc.c:3220
__alloc_pages+0x1f0/0x460 mm/page_alloc.c:4500
alloc_slab_page+0x5d/0x160 mm/slub.c:1881
allocate_slab mm/slub.c:2028 [inline]
new_slab+0x87/0x2d0 mm/slub.c:2081
___slab_alloc+0xc5d/0x12f0 mm/slub.c:3253
__slab_alloc mm/slub.c:3339 [inline]
__slab_alloc_node mm/slub.c:3392 [inline]
slab_alloc_node mm/slub.c:3485 [inline]
slab_alloc mm/slub.c:3503 [inline]
__kmem_cache_alloc_lru mm/slub.c:3510 [inline]
kmem_cache_alloc+0x1b3/0x2d0 mm/slub.c:3519
skb_clone+0x1eb/0x370 net/core/skbuff.c:1912
do_one_broadcast net/netlink/af_netlink.c:1457 [inline]
netlink_broadcast_filtered+0x658/0x1110 net/netlink/af_netlink.c:1536
netlink_broadcast+0x37/0x50 net/netlink/af_netlink.c:1560
uevent_net_broadcast_untagged lib/kobject_uevent.c:331 [inline]
kobject_uevent_net_broadcast+0x364/0x530 lib/kobject_uevent.c:409
kobject_uevent_env+0x550/0x8b0 lib/kobject_uevent.c:608
kobject_synth_uevent+0x582/0xbc0 lib/kobject_uevent.c:208
uevent_store+0x4c/0x70 drivers/base/bus.c:635
kernfs_fop_write_iter+0x3b6/0x520 fs/kernfs/file.c:352
call_write_iter include/linux/fs.h:2018 [inline]
new_sync_write fs/read_write.c:491 [inline]
vfs_write+0x46c/0x990 fs/read_write.c:584
page last free stack trace:
reset_page_owner include/linux/page_owner.h:24 [inline]
free_pages_prepare mm/page_alloc.c:1181 [inline]
free_unref_page_prepare+0x7b2/0x8c0 mm/page_alloc.c:2365
free_unref_page+0x32/0x2e0 mm/page_alloc.c:2458
discard_slab mm/slub.c:2127 [inline]
__unfreeze_partials+0x1cf/0x210 mm/slub.c:2667
put_cpu_partial+0x17c/0x250 mm/slub.c:2743
__slab_free+0x319/0x400 mm/slub.c:3700
qlink_free mm/kasan/quarantine.c:166 [inline]
qlist_free_all+0x75/0xd0 mm/kasan/quarantine.c:185
kasan_quarantine_reduce+0x143/0x160 mm/kasan/quarantine.c:292
__kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:306
kasan_slab_alloc include/linux/kasan.h:188 [inline]
slab_post_alloc_hook+0x6e/0x4b0 mm/slab.h:767
slab_alloc_node mm/slub.c:3495 [inline]
__kmem_cache_alloc_node+0x13a/0x250 mm/slub.c:3534
kmalloc_trace+0x2a/0xe0 mm/slab_common.c:1098
kmalloc include/linux/slab.h:600 [inline]
kzalloc include/linux/slab.h:721 [inline]
kernfs_fop_open+0x3f5/0xcc0 fs/kernfs/file.c:690
do_dentry_open+0x8c6/0x1500 fs/open.c:929
do_open fs/namei.c:3640 [inline]
path_openat+0x27f1/0x3230 fs/namei.c:3797
do_filp_open+0x1f5/0x430 fs/namei.c:3824
do_sys_openat2+0x134/0x1d0 fs/open.c:1421
Memory state around the buggy address:
ffff888026b29c80: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888026b29d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fc fc
>ffff888026b29d80: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb
^
ffff888026b29e00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888026b29e80: fb fb fb fb fb fb fc fc fc fc fc fc fc fc fc fc
==================================================================
---
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:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title
If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)
If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report
If you want to undo deduplication, reply with:
#syz undup
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