Message-ID: <691c16fd.a70a0220.f6df1.0054.GAE@google.com>
Date: Mon, 17 Nov 2025 22:49:33 -0800
From: syzbot <syzbot+4d6b203d625d2f57d4ca@...kaller.appspotmail.com>
To: johan.hedberg@...il.com, linux-bluetooth@...r.kernel.org, 
	linux-kernel@...r.kernel.org, luiz.dentz@...il.com, marcel@...tmann.org, 
	syzkaller-bugs@...glegroups.com
Subject: [syzbot] [bluetooth?] KASAN: slab-use-after-free Read in hci_cmd_work (2)

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=16e42fcd980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=873352b3ee3a5f48
dashboard link: https://syzkaller.appspot.com/bug?extid=4d6b203d625d2f57d4ca
compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/d8d032a78b87/disk-0f299569.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/cf21de5b7c96/vmlinux-0f299569.xz
kernel image: https://storage.googleapis.com/syzbot-assets/4472182fc485/bzImage-0f299569.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+4d6b203d625d2f57d4ca@...kaller.appspotmail.com

Bluetooth: hci3: unexpected cc 0x0c03 length: 249 > 1
Bluetooth: hci4: unexpected cc 0x0c03 length: 249 > 1
Bluetooth: hci1: unexpected cc 0x1003 length: 249 > 9
Bluetooth: hci2: unexpected cc 0x0c03 length: 249 > 1
==================================================================
BUG: KASAN: slab-use-after-free in hci_cmd_work+0x5d0/0x7b0 net/bluetooth/hci_core.c:4174
Read of size 2 at addr ffff888061d8f538 by task kworker/u9:5/5835

CPU: 1 UID: 0 PID: 5835 Comm: kworker/u9:5 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Workqueue: hci4 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 52:
 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_read_local_features_sync net/bluetooth/hci_sync.c:3708 [inline]
 hci_init_stage_sync net/bluetooth/hci_sync.c:3623 [inline]
 hci_init1_sync net/bluetooth/hci_sync.c:3755 [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+0x14b2/0x2dc0 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 5839:
 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 ffff888061d8f500
 which belongs to the cache skbuff_head_cache of size 240
The buggy address is located 56 bytes inside of
 freed 240-byte region [ffff888061d8f500, ffff888061d8f5f0)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x61d8f
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000000 ffff8881416a0a00 dead000000000122 0000000000000000
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 5835, tgid 5835 (kworker/u9:5), ts 69895228046, free_ts 69894023338
 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_noprof+0x40f/0x700 mm/slub.c:5265
 skb_clone+0x212/0x3a0 net/core/skbuff.c:2069
 hci_event_packet+0x1a6/0x1260 net/bluetooth/hci_event.c:7667
 hci_rx_work+0x45d/0xfc0 net/bluetooth/hci_core.c:4099
 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
page last free pid 2 tgid 2 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
 __kasan_populate_vmalloc_do mm/kasan/shadow.c:393 [inline]
 __kasan_populate_vmalloc+0x1b2/0x1d0 mm/kasan/shadow.c:424
 kasan_populate_vmalloc include/linux/kasan.h:579 [inline]
 alloc_vmap_area+0xdca/0x1500 mm/vmalloc.c:2124
 __get_vm_area_node+0x1f8/0x300 mm/vmalloc.c:3220
 __vmalloc_node_range_noprof+0x365/0x1640 mm/vmalloc.c:3981
 __vmalloc_node_noprof+0xc2/0x110 mm/vmalloc.c:4081
 alloc_thread_stack_node kernel/fork.c:311 [inline]
 dup_task_struct+0x3d4/0x830 kernel/fork.c:880
 copy_process+0x4ea/0x3930 kernel/fork.c:2011
 kernel_clone+0x21e/0x850 kernel/fork.c:2609
 kernel_thread+0x10d/0x160 kernel/fork.c:2670
 create_kthread kernel/kthread.c:486 [inline]
 kthreadd+0x575/0x770 kernel/kthread.c:844
 ret_from_fork+0x599/0xb30 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246

Memory state around the buggy address:
 ffff888061d8f400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888061d8f480: fb fb fb fb fb fb fc fc fc fc fc fc fc fc fc fc
>ffff888061d8f500: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                        ^
 ffff888061d8f580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fc fc
 ffff888061d8f600: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb
==================================================================


---
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