[moderation] [smc?] KCSAN: data-race in smc_switch_to_fallback / sock_poll (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 5fd0a1df5d05 Merge tag 'v6.19rc8-smb3-client-fixes' of git..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1070aa5a580000
kernel config: https://syzkaller.appspot.com/x/.config?x=8e27f4588a0f2183
dashboard link: https://syzkaller.appspot.com/bug?extid=2364c702812dfd7bbde9
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
CC: [ali...@linux.alibaba.com da...@davemloft.net dus...@linux.alibaba.com edum...@google.com gu...@linux.alibaba.com ho...@kernel.org ku...@kernel.org linux-...@vger.kernel.org linux...@vger.kernel.org linux...@vger.kernel.org mjam...@linux.ibm.com net...@vger.kernel.org pab...@redhat.com sid...@linux.ibm.com ton...@linux.alibaba.com wen...@linux.ibm.com]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/a09cd69509c3/disk-5fd0a1df.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/f218ec1eb157/vmlinux-5fd0a1df.xz
kernel image: https://storage.googleapis.com/syzbot-assets/8549229eee91/bzImage-5fd0a1df.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+2364c7...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in smc_switch_to_fallback / sock_poll

write to 0xffff888127398c18 of 8 bytes by task 14369 on cpu 1:
smc_switch_to_fallback+0x4ea/0x7e0 net/smc/af_smc.c:933
smc_sendmsg+0xce/0x2f0 net/smc/af_smc.c:2797
sock_sendmsg_nosec net/socket.c:727 [inline]
__sock_sendmsg net/socket.c:742 [inline]
____sys_sendmsg+0x5af/0x600 net/socket.c:2592
___sys_sendmsg+0x195/0x1e0 net/socket.c:2646
__sys_sendmsg net/socket.c:2678 [inline]
__do_sys_sendmsg net/socket.c:2683 [inline]
__se_sys_sendmsg net/socket.c:2681 [inline]
__x64_sys_sendmsg+0xd4/0x160 net/socket.c:2681
x64_sys_call+0x17ba/0x3000 arch/x86/include/generated/asm/syscalls_64.h:47
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 0xffff888127398c18 of 8 bytes by task 14367 on cpu 0:
sock_poll+0x27/0x240 net/socket.c:1427
vfs_poll include/linux/poll.h:82 [inline]
__io_arm_poll_handler+0x1ee/0xb80 io_uring/poll.c:581
io_poll_add+0x69/0xf0 io_uring/poll.c:899
__io_issue_sqe+0xfd/0x2d0 io_uring/io_uring.c:1793
io_issue_sqe+0x20b/0xc20 io_uring/io_uring.c:1816
io_queue_sqe io_uring/io_uring.c:2043 [inline]
io_submit_sqe io_uring/io_uring.c:2321 [inline]
io_submit_sqes+0x78a/0x11b0 io_uring/io_uring.c:2435
__do_sys_io_uring_enter io_uring/io_uring.c:3285 [inline]
__se_sys_io_uring_enter+0x1bf/0x1c70 io_uring/io_uring.c:3224
__x64_sys_io_uring_enter+0x78/0x90 io_uring/io_uring.c:3224
x64_sys_call+0x27e4/0x3000 arch/x86/include/generated/asm/syscalls_64.h:427
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: 0xffff88811a6056c0 -> 0xffff88811a606080

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 14367 Comm: syz.8.3658 Not tainted syzkaller #0 PREEMPT(voluntary)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
==================================================================


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