Subject: [syzbot] [bluetooth?] linux-next test error: KASAN: slab-use-after-free Read in hci_cmd_work

From: syzbot <[email-masked]>
Date: Fri, 14 Nov 2025 11:19:23 -0800

Hello,

syzbot found the following issue on:

HEAD commit:    0f2995693867 Add linux-next specific files for 20251114
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=12eb497c580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=29b24388a21e66c8
dashboard link: https://syzkaller.appspot.com/bug?extid=25e9c406cbd26c66c417
compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/5c41eeba33d0/disk-0f299569.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/f7188c6a90b9/vmlinux-0f299569.xz
kernel image: https://storage.googleapis.com/syzbot-assets/3c2ae5e022bf/bzImage-0f299569.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: [email-masked]

==================================================================
BUG: KASAN: slab-use-after-free in hci_cmd_work+0x5d0/0x7b0 net/bluetooth/hci_core.c:4174
Read of size 2 at addr ffff8880298b47b8 by task kworker/u9:0/52

CPU: 0 UID: 0 PID: 52 Comm: kworker/u9:0 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Workqueue: hci0 hci_cmd_work
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0xca/0x240 mm/kasan/report.c:482
 kasan_report+0x118/0x150 mm/kasan/report.c:595
 hci_cmd_work+0x5d0/0x7b0 net/bluetooth/hci_core.c:4174
 process_one_work+0x93a/0x15e0 kernel/workqueue.c:3261
 process_scheduled_works kernel/workqueue.c:3344 [inline]
 worker_thread+0x9b0/0xee0 kernel/workqueue.c:3425
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x599/0xb30 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
 </TASK>

Allocated by task 5146:
 kasan_save_stack mm/kasan/common.c:56 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:77
 unpoison_slab_object mm/kasan/common.c:339 [inline]
 __kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:365
 kasan_slab_alloc include/linux/kasan.h:252 [inline]
 slab_post_alloc_hook mm/slub.c:4948 [inline]
 slab_alloc_node mm/slub.c:5258 [inline]
 kmem_cache_alloc_node_noprof+0x43c/0x710 mm/slub.c:5310
 __alloc_skb+0x112/0x2d0 net/core/skbuff.c:664
 alloc_skb include/linux/skbuff.h:1383 [inline]
 bt_skb_alloc include/net/bluetooth/bluetooth.h:510 [inline]
 hci_cmd_sync_alloc+0x3d/0x3b0 net/bluetooth/hci_sync.c:58
 hci_cmd_sync_add net/bluetooth/hci_sync.c:99 [inline]
 __hci_cmd_sync_sk+0x1a7/0xc70 net/bluetooth/hci_sync.c:168
 __hci_cmd_sync_status_sk net/bluetooth/hci_sync.c:263 [inline]
 __hci_cmd_sync_status net/bluetooth/hci_sync.c:287 [inline]
 hci_reset_sync+0x4a/0x140 net/bluetooth/hci_sync.c:3664
 hci_init1_sync net/bluetooth/hci_sync.c:3750 [inline]
 hci_init_sync net/bluetooth/hci_sync.c:4874 [inline]
 hci_dev_init_sync net/bluetooth/hci_sync.c:5066 [inline]
 hci_dev_open_sync+0xec5/0x2dc0 net/bluetooth/hci_sync.c:5144
 hci_dev_do_open net/bluetooth/hci_core.c:430 [inline]
 hci_power_on+0x1b4/0x720 net/bluetooth/hci_core.c:959
 process_one_work+0x93a/0x15e0 kernel/workqueue.c:3261
 process_scheduled_works kernel/workqueue.c:3344 [inline]
 worker_thread+0x9b0/0xee0 kernel/workqueue.c:3425
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x599/0xb30 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246

Freed by task 6466:
 kasan_save_stack mm/kasan/common.c:56 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:77
 kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:584
 poison_slab_object mm/kasan/common.c:252 [inline]
 __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:284
 kasan_slab_free include/linux/kasan.h:234 [inline]
 slab_free_hook mm/slub.c:2540 [inline]
 slab_free mm/slub.c:6663 [inline]
 kmem_cache_free+0x197/0x640 mm/slub.c:6774
 kfree_skb_reason include/linux/skbuff.h:1322 [inline]
 kfree_skb include/linux/skbuff.h:1331 [inline]
 vhci_read+0x49a/0x5b0 drivers/bluetooth/hci_vhci.c:593
 vfs_read+0x200/0xa30 fs/read_write.c:570
 ksys_read+0x145/0x250 fs/read_write.c:715
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff8880298b4780
 which belongs to the cache skbuff_head_cache of size 240
The buggy address is located 56 bytes inside of
 freed 240-byte region [ffff8880298b4780, ffff8880298b4870)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x298b4
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000000 ffff888140a83a00 ffffea0000a62800 dead000000000004
raw: 0000000000000000 00000000000c000c 00000000f5000000 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 0x52cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP), pid 5204, tgid 5204 (udevd), ts 26856381311, free_ts 26853873462
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x240/0x2a0 mm/page_alloc.c:1851
 prep_new_page mm/page_alloc.c:1859 [inline]
 get_page_from_freelist+0x2365/0x2440 mm/page_alloc.c:3920
 __alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:5215
 alloc_pages_mpol+0x232/0x4a0 mm/mempolicy.c:2486
 alloc_slab_page mm/slub.c:3075 [inline]
 allocate_slab+0x86/0x3b0 mm/slub.c:3248
 new_slab mm/slub.c:3302 [inline]
 ___slab_alloc+0xf56/0x1990 mm/slub.c:4651
 __slab_alloc+0x65/0x100 mm/slub.c:4774
 __slab_alloc_node mm/slub.c:4850 [inline]
 slab_alloc_node mm/slub.c:5246 [inline]
 kmem_cache_alloc_node_noprof+0x4ce/0x710 mm/slub.c:5310
 __alloc_skb+0x112/0x2d0 net/core/skbuff.c:664
 alloc_skb include/linux/skbuff.h:1383 [inline]
 alloc_skb_with_frags+0xca/0x890 net/core/skbuff.c:6694
 sock_alloc_send_pskb+0x84d/0x980 net/core/sock.c:2995
 unix_dgram_sendmsg+0x461/0x1850 net/unix/af_unix.c:2133
 sock_sendmsg_nosec net/socket.c:727 [inline]
 __sock_sendmsg+0x21c/0x270 net/socket.c:746
 sock_write_iter+0x279/0x360 net/socket.c:1199
 new_sync_write fs/read_write.c:593 [inline]
 vfs_write+0x5c9/0xb30 fs/read_write.c:686
 ksys_write+0x145/0x250 fs/read_write.c:738
page last free pid 5197 tgid 5197 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1395 [inline]
 __free_frozen_pages+0xbc8/0xd30 mm/page_alloc.c:2948
 discard_slab mm/slub.c:3346 [inline]
 __put_partials+0x146/0x170 mm/slub.c:3886
 put_cpu_partial+0x1f2/0x2e0 mm/slub.c:3961
 __slab_free+0x288/0x2a0 mm/slub.c:5947
 qlink_free mm/kasan/quarantine.c:163 [inline]
 qlist_free_all+0x97/0x100 mm/kasan/quarantine.c:179
 kasan_quarantine_reduce+0x148/0x160 mm/kasan/quarantine.c:286
 __kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:349
 kasan_slab_alloc include/linux/kasan.h:252 [inline]
 slab_post_alloc_hook mm/slub.c:4948 [inline]
 slab_alloc_node mm/slub.c:5258 [inline]
 kmem_cache_alloc_noprof+0x37d/0x700 mm/slub.c:5265
 getname_flags+0xb8/0x540 fs/namei.c:146
 getname include/linux/fs.h:2522 [inline]
 do_sys_openat2+0xbc/0x1c0 fs/open.c:1428
 do_sys_open fs/open.c:1449 [inline]
 __do_sys_openat fs/open.c:1465 [inline]
 __se_sys_openat fs/open.c:1460 [inline]
 __x64_sys_openat+0x138/0x170 fs/open.c:1460
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff8880298b4680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880298b4700: fb fb fb fb fb fb fc fc fc fc fc fc fc fc fc fc
>ffff8880298b4780: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                        ^
 ffff8880298b4800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fc fc
 ffff8880298b4880: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb
==================================================================

---
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