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KASAN: slab-use-after-free Read in hci_cmd_timeout

Status: upstream: reported on 2026/05/21 13:13
Reported-by: syzbot+634ac5df6d1363cb70da@syzkaller.appspotmail.com
First crash: 5d21h, last: 5d21h
▶ ▼ Similar bugs (6)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: slab-use-after-free Read in hci_cmd_timeout bluetooth 19 28 655d 801d 0/29 auto-obsoleted due to no activity on 2024/10/24 09:00
linux-4.19 KASAN: use-after-free Read in hci_cmd_timeout 19 syz error 17 1212d 2460d 0/1 upstream: reported syz repro on 2019/09/01 02:37
android-5-10 KASAN: use-after-free Read in hci_cmd_timeout 19 1 1183d 1183d 0/2 auto-obsoleted due to no activity on 2023/05/29 20:38
linux-6.1 KASAN: use-after-free Read in hci_cmd_timeout 19 4 561d 653d 0/3 auto-obsoleted due to no activity on 2025/02/19 13:57
linux-4.14 KASAN: use-after-free Read in hci_cmd_timeout 19 C inconclusive 11 1590d 2454d 0/1 upstream: reported C repro on 2019/09/06 20:31
upstream KASAN: use-after-free Read in hci_cmd_timeout 19 C done error 371 1264d 2577d 22/29 fixed on 2023/04/12 21:18

Sample crash report:
==================================================================
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
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/05/21 13:12 linux-6.6.y eac8889a3a1c e195359d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in hci_cmd_timeout
* Struck through repros no longer work on HEAD.