syzbot

 sign-in | mailing list | source | docs
🐞 Open [827]
🐞 Fixed [87]
🐞 Invalid [1199]
⬇ Missing Backports [133]
≡ Crashes
Kernel Health Bugs/Month Bug Lifetimes Fuzzing
💬 Send us feedback

KASAN: use-after-free Read in hci_ncmd_timeout (2)

Status: upstream: reported on 2026/01/26 04:50
Reported-by: syzbot+9e2a46ca998709bbc728@syzkaller.appspotmail.com
First crash: 1d02h, last: 1d02h
▶ ▼ Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-5.15 KASAN: use-after-free Read in hci_ncmd_timeout 19 1 515d 515d 0/3 auto-obsoleted due to no activity on 2024/12/08 00:12

Sample crash report:
Bluetooth: hci1: Controller not accepting commands anymore: ncmd = 0
==================================================================
BUG: KASAN: use-after-free in instrument_atomic_read include/linux/instrumented.h:71 [inline]
BUG: KASAN: use-after-free in test_bit include/asm-generic/bitops/instrumented-non-atomic.h:134 [inline]
BUG: KASAN: use-after-free in hci_ncmd_timeout+0x7a/0x200 net/bluetooth/hci_core.c:2802
Read of size 8 at addr ffff88802a3680a8 by task kworker/1:8/5061

CPU: 1 PID: 5061 Comm: kworker/1:8 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Workqueue: events hci_ncmd_timeout
Call Trace:
 <TASK>
 dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106
 print_address_description+0x60/0x2d0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:434 [inline]
 kasan_report+0xdf/0x130 mm/kasan/report.c:451
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x235/0x290 mm/kasan/generic.c:189
 instrument_atomic_read include/linux/instrumented.h:71 [inline]
 test_bit include/asm-generic/bitops/instrumented-non-atomic.h:134 [inline]
 hci_ncmd_timeout+0x7a/0x200 net/bluetooth/hci_core.c:2802
 process_one_work+0x85f/0x1010 kernel/workqueue.c:2310
 worker_thread+0xaa6/0x1290 kernel/workqueue.c:2457
 kthread+0x436/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>

Allocated by task 4186:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track mm/kasan/common.c:46 [inline]
 set_alloc_info mm/kasan/common.c:434 [inline]
 ____kasan_kmalloc mm/kasan/common.c:513 [inline]
 __kasan_kmalloc+0xb5/0xf0 mm/kasan/common.c:522
 kmalloc include/linux/slab.h:612 [inline]
 kzalloc include/linux/slab.h:738 [inline]
 hci_alloc_dev_priv+0x23/0x1d20 net/bluetooth/hci_core.c:3775
 hci_alloc_dev include/net/bluetooth/hci_core.h:1242 [inline]
 __vhci_create_device drivers/bluetooth/hci_vhci.c:102 [inline]
 vhci_create_device+0x122/0x5c0 drivers/bluetooth/hci_vhci.c:153
 vhci_get_user drivers/bluetooth/hci_vhci.c:210 [inline]
 vhci_write+0x391/0x450 drivers/bluetooth/hci_vhci.c:290
 call_write_iter include/linux/fs.h:2173 [inline]
 new_sync_write fs/read_write.c:507 [inline]
 vfs_write+0x745/0xd60 fs/read_write.c:594
 ksys_write+0x152/0x260 fs/read_write.c:647
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0

Freed by task 4186:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:46
 kasan_set_free_info+0x1f/0x40 mm/kasan/generic.c:360
 ____kasan_slab_free+0xd5/0x110 mm/kasan/common.c:366
 kasan_slab_free include/linux/kasan.h:230 [inline]
 slab_free_hook mm/slub.c:1710 [inline]
 slab_free_freelist_hook+0xea/0x170 mm/slub.c:1736
 slab_free mm/slub.c:3504 [inline]
 kfree+0xef/0x2a0 mm/slub.c:4564
 hci_release_dev+0x138e/0x1500 net/bluetooth/hci_core.c:4096
 bt_host_release+0x7e/0x90 net/bluetooth/hci_sysfs.c:85
 device_release+0x92/0x1c0 drivers/base/core.c:-1
 kobject_cleanup lib/kobject.c:713 [inline]
 kobject_release lib/kobject.c:744 [inline]
 kref_put include/linux/kref.h:65 [inline]
 kobject_put+0x21d/0x460 lib/kobject.c:761
 vhci_release+0x7b/0xc0 drivers/bluetooth/hci_vhci.c:346
 __fput+0x234/0x930 fs/file_table.c:311
 task_work_run+0x125/0x1a0 kernel/task_work.c:188
 exit_task_work include/linux/task_work.h:33 [inline]
 do_exit+0x626/0x20c0 kernel/exit.c:883
 do_group_exit+0x12e/0x300 kernel/exit.c:997
 __do_sys_exit_group kernel/exit.c:1008 [inline]
 __se_sys_exit_group kernel/exit.c:1006 [inline]
 __x64_sys_exit_group+0x3b/0x40 kernel/exit.c:1006
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0

Last potentially related work creation:
 kasan_save_stack+0x35/0x60 mm/kasan/common.c:38
 kasan_record_aux_stack+0xb8/0x100 mm/kasan/generic.c:348
 insert_work+0x54/0x3d0 kernel/workqueue.c:1366
 __queue_work+0x9c5/0xd50 kernel/workqueue.c:1532
 call_timer_fn+0x17b/0x540 kernel/time/timer.c:1451
 expire_timers kernel/time/timer.c:1491 [inline]
 __run_timers+0x565/0x7f0 kernel/time/timer.c:1767
 run_timer_softirq+0x63/0xf0 kernel/time/timer.c:1780
 handle_softirqs+0x339/0x830 kernel/softirq.c:576
 __do_softirq kernel/softirq.c:610 [inline]
 invoke_softirq kernel/softirq.c:450 [inline]
 __irq_exit_rcu+0x13b/0x230 kernel/softirq.c:659
 irq_exit_rcu+0x5/0x20 kernel/softirq.c:671
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1108 [inline]
 sysvec_apic_timer_interrupt+0xa0/0xc0 arch/x86/kernel/apic/apic.c:1108
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676

Second to last potentially related work creation:
 kasan_save_stack+0x35/0x60 mm/kasan/common.c:38
 kasan_record_aux_stack+0xb8/0x100 mm/kasan/generic.c:348
 insert_work+0x54/0x3d0 kernel/workqueue.c:1366
 __queue_work+0x9c5/0xd50 kernel/workqueue.c:1532
 queue_work_on+0x124/0x1f0 kernel/workqueue.c:1559
 queue_work include/linux/workqueue.h:512 [inline]
 hci_recv_frame+0x18c/0x1f0 net/bluetooth/hci_core.c:4160
 vhci_get_user drivers/bluetooth/hci_vhci.c:194 [inline]
 vhci_write+0x33f/0x450 drivers/bluetooth/hci_vhci.c:290
 call_write_iter include/linux/fs.h:2173 [inline]
 new_sync_write fs/read_write.c:507 [inline]
 vfs_write+0x745/0xd60 fs/read_write.c:594
 ksys_write+0x152/0x260 fs/read_write.c:647
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0

The buggy address belongs to the object at ffff88802a368000
 which belongs to the cache kmalloc-8k of size 8192
The buggy address is located 168 bytes inside of
 8192-byte region [ffff88802a368000, ffff88802a36a000)
The buggy address belongs to the page:
page:ffffea0000a8da00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x2a368
head:ffffea0000a8da00 order:3 compound_mapcount:0 compound_pincount:0
flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000010200 dead000000000100 dead000000000122 ffff888016c42280
raw: 0000000000000000 0000000000020002 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 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 4186, ts 60148790534, free_ts 59938218273
 prep_new_page mm/page_alloc.c:2426 [inline]
 get_page_from_freelist+0x1bbd/0x1ca0 mm/page_alloc.c:4192
 __alloc_pages+0x1ee/0x480 mm/page_alloc.c:5487
 alloc_slab_page mm/slub.c:1780 [inline]
 allocate_slab mm/slub.c:1917 [inline]
 new_slab+0xc0/0x4b0 mm/slub.c:1980
 ___slab_alloc+0x80a/0xdd0 mm/slub.c:3013
 __slab_alloc mm/slub.c:3100 [inline]
 slab_alloc_node mm/slub.c:3191 [inline]
 slab_alloc mm/slub.c:3233 [inline]
 __kmalloc+0x1cd/0x330 mm/slub.c:4408
 kmalloc include/linux/slab.h:612 [inline]
 kzalloc include/linux/slab.h:738 [inline]
 hci_alloc_dev_priv+0x23/0x1d20 net/bluetooth/hci_core.c:3775
 hci_alloc_dev include/net/bluetooth/hci_core.h:1242 [inline]
 __vhci_create_device drivers/bluetooth/hci_vhci.c:102 [inline]
 vhci_create_device+0x122/0x5c0 drivers/bluetooth/hci_vhci.c:153
 vhci_get_user drivers/bluetooth/hci_vhci.c:210 [inline]
 vhci_write+0x391/0x450 drivers/bluetooth/hci_vhci.c:290
 call_write_iter include/linux/fs.h:2173 [inline]
 new_sync_write fs/read_write.c:507 [inline]
 vfs_write+0x745/0xd60 fs/read_write.c:594
 ksys_write+0x152/0x260 fs/read_write.c:647
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1340 [inline]
 free_pcp_prepare mm/page_alloc.c:1391 [inline]
 free_unref_page_prepare+0x637/0x6c0 mm/page_alloc.c:3317
 free_unref_page+0x8f/0x2a0 mm/page_alloc.c:3396
 put_page include/linux/mm.h:1258 [inline]
 __skb_frag_unref include/linux/skbuff.h:3254 [inline]
 skb_release_data+0x3b1/0x800 net/core/skbuff.c:672
 skb_release_all net/core/skbuff.c:742 [inline]
 __kfree_skb+0x4c/0x60 net/core/skbuff.c:756
 sk_eat_skb include/net/sock.h:2792 [inline]
 tcp_recvmsg_locked+0x14e1/0x27f0 net/ipv4/tcp.c:2517
 tcp_recvmsg+0x232/0x770 net/ipv4/tcp.c:2563
 inet_recvmsg+0x146/0x200 net/ipv4/af_inet.c:868
 sock_recvmsg_nosec net/socket.c:968 [inline]
 sock_recvmsg net/socket.c:986 [inline]
 sock_read_iter+0x2b8/0x380 net/socket.c:1067
 call_read_iter include/linux/fs.h:2167 [inline]
 new_sync_read fs/read_write.c:404 [inline]
 vfs_read+0x759/0xd60 fs/read_write.c:485
 ksys_read+0x152/0x260 fs/read_write.c:623
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0

Memory state around the buggy address:
 ffff88802a367f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88802a368000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88802a368080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                  ^
 ffff88802a368100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88802a368180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/01/26 04:49 linux-5.15.y 9eec9a14ee10 55756628 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in hci_ncmd_timeout
* Struck through repros no longer work on HEAD.