[syzbot] [bluetooth?] KCSAN: data-race in bacpy / memcmp

[syzbot <syzbot+dabcf90d3a2acf24b4a3@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    72c395024dac Merge tag 'docs-7.0' of git://git.kernel.org/..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16b38ae6580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=c653aa4dc2fe740b
dashboard link: https://syzkaller.appspot.com/bug?extid=dabcf90d3a2acf24b4a3
compiler:       Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/c143500d000f/disk-72c39502.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/734418a35433/vmlinux-72c39502.xz
kernel image: https://storage.googleapis.com/syzbot-assets/97548c6e5a9b/bzImage-72c39502.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+dabcf90d3a2acf24b4a3@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in bacpy / memcmp

write to 0xffff888199203818 of 6 bytes by task 18359 on cpu 1:
 bacpy+0x1e/0x30 include/net/bluetooth/bluetooth.h:380
 l2cap_sock_bind+0x275/0x5b0 net/bluetooth/l2cap_sock.c:132
 __sys_bind_socket net/socket.c:1874 [inline]
 __sys_bind+0x1d0/0x290 net/socket.c:1905
 __do_sys_bind net/socket.c:1910 [inline]
 __se_sys_bind net/socket.c:1908 [inline]
 __x64_sys_bind+0x3f/0x50 net/socket.c:1908
 x64_sys_call+0x2ceb/0x3000 arch/x86/include/generated/asm/syscalls_64.h:50
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc0/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88819920381b of 1 bytes by task 18360 on cpu 0:
 memcmp+0x52/0x90 lib/string.c:694
 memcmp include/linux/fortify-string.h:727 [inline]
 bacmp+0x1e/0x30 include/net/bluetooth/bluetooth.h:376
 l2cap_sock_connect+0x25a/0x4c0 net/bluetooth/l2cap_sock.c:218
 __sys_connect_file net/socket.c:2089 [inline]
 __sys_connect+0x1f1/0x2a0 net/socket.c:2108
 __do_sys_connect net/socket.c:2114 [inline]
 __se_sys_connect net/socket.c:2111 [inline]
 __x64_sys_connect+0x3f/0x50 net/socket.c:2111
 x64_sys_call+0x2e09/0x3000 arch/x86/include/generated/asm/syscalls_64.h:43
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc0/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00 -> 0xff

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 18360 Comm: syz.0.12425 Tainted: G        W           syzkaller #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/24/2026
==================================================================


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