[v6.6] KASAN: slab-out-of-bounds Read in bt_accept_unlink

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: c2603c511feb Linux 6.6.93
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=16cb8370580000
kernel config: https://syzkaller.appspot.com/x/.config?x=486bade17c8c30b9
dashboard link: https://syzkaller.appspot.com/bug?extid=1fabcd38ec20ef641d56
compiler: Debian clang version 20.1.6 (++20250514063057+1e4d39e07757-1~exp1~20250514183223.118), Debian LLD 20.1.6

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/8754f950a6e7/disk-c2603c51.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/3b19332dbf63/vmlinux-c2603c51.xz
kernel image: https://storage.googleapis.com/syzbot-assets/cb245e836038/bzImage-c2603c51.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+1fabcd...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: slab-out-of-bounds in __list_del_entry_valid_or_report+0x84/0x130 lib/list_debug.c:62
Read of size 8 at addr ffff88807c65e510 by task syz.0.1162/9360

CPU: 0 PID: 9360 Comm: syz.0.1162 Not tainted 6.6.93-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call Trace:
<TASK>
dump_stack_lvl+0x16c/0x230 lib/dump_stack.c:106
print_address_description mm/kasan/report.c:364 [inline]
print_report+0xac/0x230 mm/kasan/report.c:475
kasan_report+0x151/0x180 mm/kasan/report.c:588
__list_del_entry_valid_or_report+0x84/0x130 lib/list_debug.c:62
__list_del_entry_valid include/linux/list.h:124 [inline]
__list_del_entry include/linux/list.h:215 [inline]
list_del_init include/linux/list.h:287 [inline]
bt_accept_unlink+0x39/0x230 net/bluetooth/af_bluetooth.c:256
l2cap_sock_teardown_cb+0x17e/0x450 net/bluetooth/l2cap_sock.c:1597
l2cap_chan_del+0xaf/0x5e0 net/bluetooth/l2cap_core.c:655
l2cap_conn_del+0x380/0x660 net/bluetooth/l2cap_core.c:1787
hci_disconn_cfm include/net/bluetooth/hci_core.h:1982 [inline]
hci_conn_hash_flush+0x107/0x220 net/bluetooth/hci_conn.c:2539
hci_dev_close_sync+0x962/0xfb0 net/bluetooth/hci_sync.c:5217
hci_dev_do_close net/bluetooth/hci_core.c:505 [inline]
hci_unregister_dev+0x206/0x500 net/bluetooth/hci_core.c:2684
vhci_release+0x83/0xd0 drivers/bluetooth/hci_vhci.c:666
__fput+0x234/0x970 fs/file_table.c:384
task_work_run+0x1ce/0x250 kernel/task_work.c:239
exit_task_work include/linux/task_work.h:43 [inline]
do_exit+0x903/0x23c0 kernel/exit.c:874
do_group_exit+0x21b/0x2d0 kernel/exit.c:1023
get_signal+0x12fc/0x1400 kernel/signal.c:2902
arch_do_signal_or_restart+0x96/0x780 arch/x86/kernel/signal.c:310
exit_to_user_mode_loop+0x70/0x110 kernel/entry/common.c:174
exit_to_user_mode_prepare+0xb1/0x140 kernel/entry/common.c:210
__syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:302
do_syscall_64+0x61/0xb0 arch/x86/entry/common.c:87
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fb2df3c11e5
Code: Unable to access opcode bytes at 0x7fb2df3c11bb.
RSP: 002b:00007fb2e02d5f80 EFLAGS: 00000293 ORIG_RAX: 00000000000000e6
RAX: 0000000000000000 RBX: 00007fb2df5b5fa0 RCX: 00007fb2df3c11e5
RDX: 00007fb2e02d5fc0 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00007fb2df410b39 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000000
R13: 0000000000000000 R14: 00007fb2df5b5fa0 R15: 00007ffd9d563668
</TASK>

Allocated by task 9350:
kasan_save_stack mm/kasan/common.c:45 [inline]
kasan_set_track+0x4e/0x70 mm/kasan/common.c:52
____kasan_kmalloc mm/kasan/common.c:374 [inline]
__kasan_kmalloc+0x8f/0xa0 mm/kasan/common.c:383
kasan_kmalloc include/linux/kasan.h:198 [inline]
__do_kmalloc_node mm/slab_common.c:1007 [inline]
__kmalloc+0xb4/0x240 mm/slab_common.c:1020
kmalloc include/linux/slab.h:604 [inline]
kzalloc include/linux/slab.h:721 [inline]
ops_init+0x8b/0x640 net/core/net_namespace.c:129
setup_net+0x3a5/0xa00 net/core/net_namespace.c:343
copy_net_ns+0x36d/0x5e0 net/core/net_namespace.c:520
create_new_namespaces+0x3d3/0x6f0 kernel/nsproxy.c:110
unshare_nsproxy_namespaces+0x11a/0x160 kernel/nsproxy.c:228
ksys_unshare+0x4c0/0x890 kernel/fork.c:3439
__do_sys_unshare kernel/fork.c:3510 [inline]
__se_sys_unshare kernel/fork.c:3508 [inline]
__x64_sys_unshare+0x38/0x40 kernel/fork.c:3508
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2

Last potentially related work creation:
kasan_save_stack+0x3e/0x60 mm/kasan/common.c:45
__kasan_record_aux_stack+0xaf/0xc0 mm/kasan/generic.c:492
__call_rcu_common kernel/rcu/tree.c:2713 [inline]
call_rcu+0x14f/0x920 kernel/rcu/tree.c:2829
netlink_release+0x16d8/0x1ad0 net/netlink/af_netlink.c:812
__sock_release net/socket.c:659 [inline]
sock_close+0xbd/0x230 net/socket.c:1421
__fput+0x234/0x970 fs/file_table.c:384
task_work_run+0x1ce/0x250 kernel/task_work.c:239
resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
exit_to_user_mode_loop+0xe6/0x110 kernel/entry/common.c:177
exit_to_user_mode_prepare+0xb1/0x140 kernel/entry/common.c:210
__syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:302
do_syscall_64+0x61/0xb0 arch/x86/entry/common.c:87
entry_SYSCALL_64_after_hwframe+0x68/0xd2

Second to last potentially related work creation:
kasan_save_stack+0x3e/0x60 mm/kasan/common.c:45
__kasan_record_aux_stack+0xaf/0xc0 mm/kasan/generic.c:492
__call_rcu_common kernel/rcu/tree.c:2713 [inline]
call_rcu+0x14f/0x920 kernel/rcu/tree.c:2829
netlink_release+0x16d8/0x1ad0 net/netlink/af_netlink.c:812
__sock_release net/socket.c:659 [inline]
sock_close+0xbd/0x230 net/socket.c:1421
__fput+0x234/0x970 fs/file_table.c:384
task_work_run+0x1ce/0x250 kernel/task_work.c:239
resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
exit_to_user_mode_loop+0xe6/0x110 kernel/entry/common.c:177
exit_to_user_mode_prepare+0xb1/0x140 kernel/entry/common.c:210
__syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:302
do_syscall_64+0x61/0xb0 arch/x86/entry/common.c:87
entry_SYSCALL_64_after_hwframe+0x68/0xd2

The buggy address belongs to the object at ffff88807c65e000
which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 248 bytes to the right of
allocated 1048-byte region [ffff88807c65e000, ffff88807c65e418)

The buggy address belongs to the physical page:
page:ffffea0001f19600 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x7c658
head:ffffea0001f19600 order:3 entire_mapcount:0 nr_pages_mapped:0 pincount:0
anon flags: 0xfff00000000840(slab|head|node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff00000000840 ffff888017842000 0000000000000000 dead000000000001
raw: 0000000000000000 0000000000080008 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 5771, tgid 5771 (syz-executor), ts 92244557503, free_ts 92224799698
set_page_owner include/linux/page_owner.h:31 [inline]
post_alloc_hook+0x1cd/0x210 mm/page_alloc.c:1554
prep_new_page mm/page_alloc.c:1561 [inline]
get_page_from_freelist+0x195c/0x19f0 mm/page_alloc.c:3191
__alloc_pages+0x1e3/0x460 mm/page_alloc.c:4457
alloc_slab_page+0x5d/0x170 mm/slub.c:1876
allocate_slab mm/slub.c:2023 [inline]
new_slab+0x87/0x2e0 mm/slub.c:2076
___slab_alloc+0xc6d/0x12f0 mm/slub.c:3230
__slab_alloc mm/slub.c:3329 [inline]
__slab_alloc_node mm/slub.c:3382 [inline]
slab_alloc_node mm/slub.c:3475 [inline]
__kmem_cache_alloc_node+0x1a2/0x260 mm/slub.c:3524
__do_kmalloc_node mm/slab_common.c:1006 [inline]
__kmalloc+0xa4/0x240 mm/slab_common.c:1020
kmalloc include/linux/slab.h:604 [inline]
kzalloc include/linux/slab.h:721 [inline]
rfkill_alloc+0xb1/0x2d0 net/rfkill/core.c:1006
wiphy_new_nm+0x107b/0x1990 net/wireless/core.c:561
ieee80211_alloc_hw_nm+0x3c8/0x1ee0 net/mac80211/main.c:697
mac80211_hwsim_new_radio+0x1e0/0x4cf0 drivers/net/wireless/virtual/mac80211_hwsim.c:4969
hwsim_new_radio_nl+0xd78/0x19d0 drivers/net/wireless/virtual/mac80211_hwsim.c:5983
genl_family_rcv_msg_doit+0x209/0x2f0 net/netlink/genetlink.c:971
genl_family_rcv_msg net/netlink/genetlink.c:1051 [inline]
genl_rcv_msg+0x60b/0x790 net/netlink/genetlink.c:1066
netlink_rcv_skb+0x216/0x480 net/netlink/af_netlink.c:2537
page last free stack trace:
reset_page_owner include/linux/page_owner.h:24 [inline]
free_pages_prepare mm/page_alloc.c:1154 [inline]
free_unref_page_prepare+0x7ce/0x8e0 mm/page_alloc.c:2336
free_unref_page+0x32/0x2e0 mm/page_alloc.c:2429
discard_slab mm/slub.c:2122 [inline]
__unfreeze_partials+0x1cf/0x210 mm/slub.c:2662
put_cpu_partial+0x17c/0x250 mm/slub.c:2738
__slab_free+0x31d/0x410 mm/slub.c:3686
qlink_free mm/kasan/quarantine.c:166 [inline]
qlist_free_all+0x75/0xe0 mm/kasan/quarantine.c:185
kasan_quarantine_reduce+0x143/0x160 mm/kasan/quarantine.c:292
__kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:305
kasan_slab_alloc include/linux/kasan.h:188 [inline]
slab_post_alloc_hook+0x6e/0x4d0 mm/slab.h:767
slab_alloc_node mm/slub.c:3485 [inline]
kmem_cache_alloc_node+0x150/0x330 mm/slub.c:3530
__alloc_skb+0x108/0x2c0 net/core/skbuff.c:640
alloc_skb include/linux/skbuff.h:1284 [inline]
nlmsg_new include/net/netlink.h:999 [inline]
netlink_ack+0x376/0x1110 net/netlink/af_netlink.c:2474
netlink_rcv_skb+0x29a/0x480 net/netlink/af_netlink.c:2543
genl_rcv+0x28/0x40 net/netlink/genetlink.c:1075
netlink_unicast_kernel net/netlink/af_netlink.c:1323 [inline]
netlink_unicast+0x750/0x8c0 net/netlink/af_netlink.c:1349
netlink_sendmsg+0x8c1/0xbe0 net/netlink/af_netlink.c:1891

Memory state around the buggy address:
ffff88807c65e400: 00 00 00 fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88807c65e480: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88807c65e500: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
^
ffff88807c65e580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88807c65e600: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.