[syzbot] [rds?] KCSAN: data-race in rds_poll / rds_sendmsg

[syzbot] [rds?] KCSAN: data-race in rds_poll / rds_sendmsg

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    e5d505e3664b Merge tag 'trace-v7.1-rc3' of git://git.kerne..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=144d37ba580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=2e40c0f41e01837e
dashboard link: https://syzkaller.appspot.com/bug?extid=fbf3648ae7f5bdb05c59
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/d01e24b29d85/disk-e5d505e3.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/763a9ed109de/vmlinux-e5d505e3.xz
kernel image: https://storage.googleapis.com/syzbot-assets/aa1f01135fd4/bzImage-e5d505e3.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+fbf3648ae7f5bdb05c59@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in rds_poll / rds_sendmsg

write to 0xffff8881054183a4 of 4 bytes by task 9010 on cpu 0:
 rds_sendmsg+0x1001/0x15b0 net/rds/send.c:1391
 sock_sendmsg_nosec net/socket.c:787 [inline]
 __sock_sendmsg net/socket.c:802 [inline]
 ____sys_sendmsg+0x563/0x5b0 net/socket.c:2698
 ___sys_sendmsg+0x195/0x1e0 net/socket.c:2752
 __sys_sendmsg net/socket.c:2784 [inline]
 __do_sys_sendmsg net/socket.c:2789 [inline]
 __se_sys_sendmsg net/socket.c:2787 [inline]
 __x64_sys_sendmsg+0xd4/0x160 net/socket.c:2787
 x64_sys_call+0x194c/0x3020 arch/x86/include/generated/asm/syscalls_64.h:47
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff8881054183a4 of 4 bytes by task 9013 on cpu 1:
 rds_poll+0x9b/0x310 net/rds/af_rds.c:222
 sock_poll+0x21c/0x240 net/socket.c:1502
 vfs_poll include/linux/poll.h:82 [inline]
 __io_arm_poll_handler+0x1ef/0xbf0 io_uring/poll.c:590
 io_arm_apoll+0x2eb/0x400 io_uring/poll.c:698
 io_arm_poll_handler+0x12f/0x160 io_uring/poll.c:727
 io_queue_async+0x25d/0x320 io_uring/io_uring.c:1634
 io_queue_sqe io_uring/io_uring.c:1660 [inline]
 io_req_task_submit+0x9b/0xa0 io_uring/io_uring.c:1062
 io_handle_tw_list+0x1f5/0x230 io_uring/tw.c:72
 tctx_task_work_run+0x42/0x140 io_uring/tw.c:132
 tctx_task_work+0x3f/0x80 io_uring/tw.c:150
 task_work_run+0x130/0x1a0 kernel/task_work.c:233
 get_signal+0xdea/0xf20 kernel/signal.c:2809
 arch_do_signal_or_restart+0x96/0x480 arch/x86/kernel/signal.c:337
 __exit_to_user_mode_loop kernel/entry/common.c:64 [inline]
 exit_to_user_mode_loop+0x6f/0x820 kernel/entry/common.c:98
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:230 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:318 [inline]
 do_syscall_64+0x232/0x3b0 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000000 -> 0x00000001

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 9013 Comm: syz.7.10555 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
==================================================================


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