Subject: [syzbot] [net?] [s390?] KCSAN: data-race in __sys_connect / smc_switch_to_fallback

From: syzbot <[email-masked]>
Date: Thu, 01 Feb 2024 02:12:25 -0800

Hello,

syzbot found the following issue on:

HEAD commit:    4854cf9c61d0 Merge tag 'mips-fixes_6.8_1' of git://git.ker..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=149d01efe80000
kernel config:  https://syzkaller.appspot.com/x/.config?x=e1bd33f45956bbc2
dashboard link: https://syzkaller.appspot.com/bug?extid=ab2213db98841b6ead07
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/e44f160651d1/disk-4854cf9c.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/f6a2062d07e6/vmlinux-4854cf9c.xz
kernel image: https://storage.googleapis.com/syzbot-assets/3d179908ef3c/bzImage-4854cf9c.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: [email-masked]

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

write to 0xffff88812a230bc8 of 8 bytes by task 1831 on cpu 1:
 smc_switch_to_fallback+0x453/0x740 net/smc/af_smc.c:924
 smc_sendmsg+0xd6/0x330 net/smc/af_smc.c:2772
 sock_sendmsg_nosec net/socket.c:730 [inline]
 __sock_sendmsg net/socket.c:745 [inline]
 ____sys_sendmsg+0x37c/0x4d0 net/socket.c:2584
 ___sys_sendmsg net/socket.c:2638 [inline]
 __sys_sendmsg+0x1e9/0x270 net/socket.c:2667
 __do_sys_sendmsg net/socket.c:2676 [inline]
 __se_sys_sendmsg net/socket.c:2674 [inline]
 __x64_sys_sendmsg+0x46/0x50 net/socket.c:2674
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x59/0x120 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

read to 0xffff88812a230bc8 of 8 bytes by task 1833 on cpu 0:
 sock_from_file net/socket.c:514 [inline]
 __sys_connect_file net/socket.c:2037 [inline]
 __sys_connect+0x11d/0x1b0 net/socket.c:2065
 __do_sys_connect net/socket.c:2075 [inline]
 __se_sys_connect net/socket.c:2072 [inline]
 __x64_sys_connect+0x41/0x50 net/socket.c:2072
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x59/0x120 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

value changed: 0xffff8881293bc000 -> 0xffff8881293bf400

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 1833 Comm: syz-executor.0 Not tainted 6.8.0-rc1-syzkaller-00385-g4854cf9c61d0 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023
==================================================================

---
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