KASAN: slab-out-of-bounds Read in bt_accept_unlink

Status: upstream: reported on 2025/12/27 18:50
Reported-by: syzbot+0234d971a151c4e17b8e@syzkaller.appspotmail.com
First crash: 208d, last: 22d
▶ ▼ Similar bugs (10)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-5.15 BUG: corrupted list in bt_accept_unlink 17 3 430d 471d 0/3 auto-obsoleted due to no activity on 2025/08/27 17:34
linux-6.6 KASAN: slab-out-of-bounds Read in bt_accept_unlink 17 1 402d 402d 0/2 auto-obsoleted due to no activity on 2025/09/25 00:09
upstream KASAN: slab-use-after-free Read in bt_accept_unlink bluetooth 19 syz 209 7h42m 640d 0/29 upstream: reported syz repro on 2024/10/21 08:47
linux-5.15 KASAN: slab-out-of-bounds Read in bt_accept_unlink 17 1 289d 289d 0/3 auto-obsoleted due to no activity on 2026/01/15 10:51
linux-6.1 KASAN: use-after-free Read in bt_accept_unlink 19 1 408d 408d 0/3 auto-obsoleted due to no activity on 2025/09/18 23:51
linux-6.6 KASAN: slab-use-after-free Read in bt_accept_unlink (2) 19 1 17d 17d 0/2 upstream: reported on 2026/07/06 20:50
linux-5.15 KASAN: use-after-free Read in bt_accept_unlink 19 1 173d 173d 0/3 auto-obsoleted due to no activity on 2026/05/11 03:38
upstream general protection fault in bt_accept_unlink (2) bluetooth 2 1 1968d 1964d 0/29 auto-closed as invalid on 2021/07/01 06:33
linux-6.6 KASAN: slab-use-after-free Read in bt_accept_unlink 19 1 293d 293d 0/2 auto-obsoleted due to no activity on 2026/01/11 02:55
linux-5.15 KASAN: use-after-free Read in bt_accept_unlink (2) 19 1 53d 53d 0/3 upstream: reported on 2026/05/31 07:00

Sample crash report:
Bluetooth: hci1: Opcode 0x0c1a failed: -4
Bluetooth: hci1: Opcode 0x0406 failed: -4
==================================================================
BUG: KASAN: slab-out-of-bounds in __list_del_entry_valid+0x80/0x120 lib/list_debug.c:59
Read of size 8 at addr ffff8880558d5518 by task syz.0.721/8045

CPU: 0 PID: 8045 Comm: syz.0.721 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x188/0x24e lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:316 [inline]
 print_report+0xa8/0x210 mm/kasan/report.c:420
 kasan_report+0x10b/0x140 mm/kasan/report.c:524
 __list_del_entry_valid+0x80/0x120 lib/list_debug.c:59
 __list_del_entry include/linux/list.h:134 [inline]
 list_del_init include/linux/list.h:206 [inline]
 bt_accept_unlink+0x35/0x230 net/bluetooth/af_bluetooth.c:232
 l2cap_sock_teardown_cb+0x1af/0x380 net/bluetooth/l2cap_sock.c:1643
 l2cap_chan_del+0xab/0x620 net/bluetooth/l2cap_core.c:680
 l2cap_conn_del+0x3c4/0x6a0 net/bluetooth/l2cap_core.c:1955
 l2cap_connect_cfm+0x119/0x1120 net/bluetooth/l2cap_core.c:8393
 hci_connect_cfm include/net/bluetooth/hci_core.h:1817 [inline]
 hci_conn_failed+0x16f/0x2a0 net/bluetooth/hci_conn.c:1248
 hci_abort_conn_sync+0xb3c/0xd50 net/bluetooth/hci_sync.c:5578
 hci_disconnect_all_sync net/bluetooth/hci_sync.c:5591 [inline]
 hci_suspend_sync+0x48a/0xdb0 net/bluetooth/hci_sync.c:6073
 hci_suspend_dev+0x199/0x320 net/bluetooth/hci_core.c:2857
 hci_suspend_notifier+0xc8/0x270 net/bluetooth/hci_core.c:2424
 notifier_call_chain kernel/notifier.c:87 [inline]
 notifier_call_chain_robust+0xe1/0x2c0 kernel/notifier.c:122
 blocking_notifier_call_chain_robust+0x66/0x90 kernel/notifier.c:347
 pm_notifier_call_chain_robust+0x28/0x60 kernel/power/main.c:90
 snapshot_open+0x19b/0x280 kernel/power/user.c:77
 misc_open+0x31f/0x390 drivers/char/misc.c:145
 chrdev_open+0x5c5/0x6a0 fs/char_dev.c:414
 do_dentry_open+0x7e9/0x10d0 fs/open.c:882
 do_open fs/namei.c:3634 [inline]
 path_openat+0x2635/0x2ee0 fs/namei.c:3791
 do_filp_open+0x1f1/0x430 fs/namei.c:3818
 do_sys_openat2+0x150/0x4b0 fs/open.c:1320
 do_sys_open fs/open.c:1336 [inline]
 __do_sys_openat fs/open.c:1352 [inline]
 __se_sys_openat fs/open.c:1347 [inline]
 __x64_sys_openat+0x135/0x160 fs/open.c:1347
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f5898b9c819
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f5899a0f028 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f5898e16090 RCX: 00007f5898b9c819
RDX: 0000000000101000 RSI: 0000200000000040 RDI: ffffffffffffff9c
RBP: 00007f5898c32c91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f5898e16128 R14: 00007f5898e16090 R15: 00007ffff71baf98
 </TASK>

Allocated by task 3637:
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:53
 ____kasan_kmalloc mm/kasan/common.c:375 [inline]
 __kasan_kmalloc+0x8e/0xa0 mm/kasan/common.c:384
 kmalloc include/linux/slab.h:563 [inline]
 kzalloc include/linux/slab.h:699 [inline]
 kernfs_iop_get_link+0x63/0x5a0 fs/kernfs/symlink.c:135
 vfs_readlink+0x179/0x3e0 fs/namei.c:5131
 do_readlinkat+0x251/0x490 fs/stat.c:480
 __do_sys_readlink fs/stat.c:501 [inline]
 __se_sys_readlink fs/stat.c:498 [inline]
 __x64_sys_readlink+0x7b/0x90 fs/stat.c:498
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

Freed by task 3637:
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:53
 kasan_save_free_info+0x2d/0x50 mm/kasan/generic.c:516
 ____kasan_slab_free+0x126/0x1e0 mm/kasan/common.c:237
 kasan_slab_free include/linux/kasan.h:177 [inline]
 slab_free_hook mm/slub.c:1729 [inline]
 slab_free_freelist_hook+0x131/0x1a0 mm/slub.c:1755
 slab_free mm/slub.c:3687 [inline]
 __kmem_cache_free+0xb6/0x1f0 mm/slub.c:3700
 do_delayed_call include/linux/delayed_call.h:28 [inline]
 vfs_readlink+0x227/0x3e0 fs/namei.c:5136
 do_readlinkat+0x251/0x490 fs/stat.c:480
 __do_sys_readlink fs/stat.c:501 [inline]
 __se_sys_readlink fs/stat.c:498 [inline]
 __x64_sys_readlink+0x7b/0x90 fs/stat.c:498
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

The buggy address belongs to the object at ffff8880558d4000
 which belongs to the cache kmalloc-4k of size 4096
The buggy address is located 1304 bytes to the right of
 4096-byte region [ffff8880558d4000, ffff8880558d5000)

The buggy address belongs to the physical page:
page:ffffea0001563400 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x558d0
head:ffffea0001563400 order:3 compound_mapcount:0 compound_pincount:0
flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000010200 0000000000000000 dead000000000001 ffff888017442140
raw: 0000000000000000 0000000000040004 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 0x1d2040(__GFP_IO|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 3637, tgid 3637 (udevd), ts 342387470491, free_ts 342346629277
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook+0x173/0x1a0 mm/page_alloc.c:2559
 prep_new_page mm/page_alloc.c:2566 [inline]
 get_page_from_freelist+0x1a1e/0x1ab0 mm/page_alloc.c:4357
 __alloc_pages+0x1ec/0x4f0 mm/page_alloc.c:5657
 alloc_slab_page+0x5d/0x160 mm/slub.c:1799
 allocate_slab mm/slub.c:1944 [inline]
 new_slab+0x87/0x2c0 mm/slub.c:1997
 ___slab_alloc+0xbc6/0x1240 mm/slub.c:3154
 __slab_alloc mm/slub.c:3240 [inline]
 slab_alloc_node mm/slub.c:3325 [inline]
 __kmem_cache_alloc_node+0x1a0/0x260 mm/slub.c:3398
 __do_kmalloc_node mm/slab_common.c:935 [inline]
 __kmalloc+0xa0/0x240 mm/slab_common.c:949
 kmalloc include/linux/slab.h:568 [inline]
 tomoyo_realpath_from_path+0xdf/0x5d0 security/tomoyo/realpath.c:251
 tomoyo_get_realpath security/tomoyo/file.c:151 [inline]
 tomoyo_check_open_permission+0x212/0x440 security/tomoyo/file.c:771
 security_file_open+0x5e/0xa0 security/security.c:1682
 do_dentry_open+0x305/0x10d0 fs/open.c:869
 do_open fs/namei.c:3634 [inline]
 path_openat+0x2635/0x2ee0 fs/namei.c:3791
 do_filp_open+0x1f1/0x430 fs/namei.c:3818
 do_sys_openat2+0x150/0x4b0 fs/open.c:1320
 do_sys_open fs/open.c:1336 [inline]
 __do_sys_openat fs/open.c:1352 [inline]
 __se_sys_openat fs/open.c:1347 [inline]
 __x64_sys_openat+0x135/0x160 fs/open.c:1347
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1486 [inline]
 free_pcp_prepare mm/page_alloc.c:1536 [inline]
 free_unref_page_prepare+0x8b4/0x9a0 mm/page_alloc.c:3413
 free_unref_page+0x2e/0x3f0 mm/page_alloc.c:3508
 qlink_free mm/kasan/quarantine.c:168 [inline]
 qlist_free_all+0x76/0xe0 mm/kasan/quarantine.c:187
 kasan_quarantine_reduce+0x144/0x160 mm/kasan/quarantine.c:294
 __kasan_slab_alloc+0x1e/0x80 mm/kasan/common.c:306
 kasan_slab_alloc include/linux/kasan.h:201 [inline]
 slab_post_alloc_hook+0x4b/0x480 mm/slab.h:737
 slab_alloc_node mm/slub.c:3359 [inline]
 __kmem_cache_alloc_node+0x140/0x260 mm/slub.c:3398
 __do_kmalloc_node mm/slab_common.c:935 [inline]
 __kmalloc+0xa0/0x240 mm/slab_common.c:949
 kmalloc include/linux/slab.h:568 [inline]
 tomoyo_realpath_from_path+0xdf/0x5d0 security/tomoyo/realpath.c:251
 tomoyo_get_realpath security/tomoyo/file.c:151 [inline]
 tomoyo_path_perm+0x26f/0x610 security/tomoyo/file.c:822
 security_inode_getattr+0xcf/0x120 security/security.c:1362
 vfs_getattr+0x26/0x3a0 fs/stat.c:158
 vfs_fstat fs/stat.c:183 [inline]
 __do_sys_newfstat fs/stat.c:447 [inline]
 __se_sys_newfstat fs/stat.c:444 [inline]
 __x64_sys_newfstat+0x13d/0x220 fs/stat.c:444
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

Memory state around the buggy address:
 ffff8880558d5400: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8880558d5480: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8880558d5500: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                            ^
 ffff8880558d5580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8880558d5600: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================

Crashes (7):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/04/15 16:58 linux-6.1.y 8e8fc038cad5 c441f497 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: slab-out-of-bounds Read in bt_accept_unlink
2026/02/20 14:41 linux-6.1.y 779f9571ac3e 17d780d6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: slab-out-of-bounds Read in bt_accept_unlink
2025/12/27 18:49 linux-6.1.y 50cbba13faa2 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: slab-out-of-bounds Read in bt_accept_unlink
2026/07/02 00:03 linux-6.1.y fdb6fcb41cc7 27192279 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Read in bt_accept_unlink
2026/04/08 06:24 linux-6.1.y 1989cd3d56e2 2c961e87 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Read in bt_accept_unlink
2026/01/31 16:33 linux-6.1.y cd9b81672742 afc0c4d4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Read in bt_accept_unlink
2026/05/08 16:29 linux-6.1.y 128a674368bf b2988c17 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in bt_accept_unlink
* Struck through repros no longer work on HEAD.