[syzbot] [rds?] KCSAN: data-race in rds_sendmsg / rds_sendmsg (3)

[syzbot <syzbot+879c1877016972360186@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    3b029c035b34 Merge tag 'cgroup-for-7.2-rc3-fixes' of git:/..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1638fb89580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=84b3039e8461eef5
dashboard link: https://syzkaller.appspot.com/bug?extid=879c1877016972360186
compiler:       Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/9ab6065d4938/disk-3b029c03.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/7373fbe29535/vmlinux-3b029c03.xz
kernel image: https://storage.googleapis.com/syzbot-assets/938cb90d037d/bzImage-3b029c03.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+879c1877016972360186@syzkaller.appspotmail.com

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

write to 0xffff888101dec818 of 8 bytes by task 30904 on cpu 0:
 rds_sendmsg+0xc1f/0x1580 net/rds/send.c:1332
 sock_sendmsg_nosec net/socket.c:775 [inline]
 __sock_sendmsg net/socket.c:790 [inline]
 ____sys_sendmsg+0x532/0x580 net/socket.c:2684
 ___sys_sendmsg+0x195/0x1e0 net/socket.c:2738
 __sys_sendmsg net/socket.c:2770 [inline]
 __do_sys_sendmsg net/socket.c:2775 [inline]
 __se_sys_sendmsg net/socket.c:2773 [inline]
 __x64_sys_sendmsg+0xd4/0x160 net/socket.c:2773
 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+0x136/0x3c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

write to 0xffff888101dec818 of 8 bytes by task 30905 on cpu 1:
 rds_sendmsg+0xc1f/0x1580 net/rds/send.c:1332
 sock_sendmsg_nosec net/socket.c:775 [inline]
 __sock_sendmsg net/socket.c:790 [inline]
 ____sys_sendmsg+0x532/0x580 net/socket.c:2684
 ___sys_sendmsg+0x195/0x1e0 net/socket.c:2738
 __sys_sendmsg net/socket.c:2770 [inline]
 __do_sys_sendmsg net/socket.c:2775 [inline]
 __se_sys_sendmsg net/socket.c:2773 [inline]
 __x64_sys_sendmsg+0xd4/0x160 net/socket.c:2773
 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+0x136/0x3c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000000000 -> 0xffff88811b61faf0

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 30905 Comm: syz.5.5733 Tainted: G        W           syzkaller #0 PREEMPT(lazy) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
==================================================================
atomic_op ffff888118e74d28 conn xmit_atomic 0000000000000000


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