netdev - Re: [syzbot] [net?] KCSAN: data-race in udpv6_sendmsg / udpv6

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Date: Fri, 12 Jan 2024 11:20:49 +0100
From: Eric Dumazet <edumazet@...gle.com>
To: syzbot <syzbot+8d482d0e407f665d9d10@...kaller.appspotmail.com>
Cc: davem@...emloft.net, dsahern@...nel.org, kuba@...nel.org, 
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org, pabeni@...hat.com, 
	syzkaller-bugs@...glegroups.com, willemdebruijn.kernel@...il.com
Subject: Re: [syzbot] [net?] KCSAN: data-race in udpv6_sendmsg / udpv6_sendmsg (6)

On Fri, Jan 12, 2024 at 11:10 AM syzbot
<syzbot+8d482d0e407f665d9d10@...kaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    0dd3ee311255 Linux 6.7
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=1713a06de80000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=1bb2daade28c90a5
> dashboard link: https://syzkaller.appspot.com/bug?extid=8d482d0e407f665d9d10
> 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/b3bdaecbc4f5/disk-0dd3ee31.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/6656b77ef58a/vmlinux-0dd3ee31.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/85fa7f08c720/bzImage-0dd3ee31.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+8d482d0e407f665d9d10@...kaller.appspotmail.com
>
> ==================================================================
> BUG: KCSAN: data-race in udpv6_sendmsg / udpv6_sendmsg
>
> write to 0xffff88814e5eadf0 of 4 bytes by task 15547 on cpu 1:
>  udpv6_sendmsg+0x1405/0x1530 net/ipv6/udp.c:1596
>  inet6_sendmsg+0x63/0x80 net/ipv6/af_inet6.c:657
>  sock_sendmsg_nosec net/socket.c:730 [inline]
>  __sock_sendmsg net/socket.c:745 [inline]
>  __sys_sendto+0x257/0x310 net/socket.c:2192
>  __do_sys_sendto net/socket.c:2204 [inline]
>  __se_sys_sendto net/socket.c:2200 [inline]
>  __x64_sys_sendto+0x78/0x90 net/socket.c:2200
>  do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>  do_syscall_64+0x44/0x110 arch/x86/entry/common.c:83
>  entry_SYSCALL_64_after_hwframe+0x63/0x6b
>
> read to 0xffff88814e5eadf0 of 4 bytes by task 15551 on cpu 0:
>  udpv6_sendmsg+0x22c/0x1530 net/ipv6/udp.c:1373
>  inet6_sendmsg+0x63/0x80 net/ipv6/af_inet6.c:657
>  sock_sendmsg_nosec net/socket.c:730 [inline]
>  __sock_sendmsg net/socket.c:745 [inline]
>  ____sys_sendmsg+0x37c/0x4d0 net/socket.c:2586
>  ___sys_sendmsg net/socket.c:2640 [inline]
>  __sys_sendmmsg+0x269/0x500 net/socket.c:2726
>  __do_sys_sendmmsg net/socket.c:2755 [inline]
>  __se_sys_sendmmsg net/socket.c:2752 [inline]
>  __x64_sys_sendmmsg+0x57/0x60 net/socket.c:2752
>  do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>  do_syscall_64+0x44/0x110 arch/x86/entry/common.c:83
>  entry_SYSCALL_64_after_hwframe+0x63/0x6b
>
> value changed: 0x00000000 -> 0x0000000a
>
> Reported by Kernel Concurrency Sanitizer on:
> CPU: 0 PID: 15551 Comm: syz-executor.1 Tainted: G        W          6.7.0-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023
> ==================================================================
>
>
> ---
> This report is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@...glegroups.com.
>
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
>
> If the report is already addressed, let syzbot know by replying with:
> #syz fix: exact-commit-title
>
> If you want to overwrite report's subsystems, reply with:
> #syz set subsystems: new-subsystem
> (See the list of subsystem names on the web dashboard)
>
> If the report is a duplicate of another one, reply with:
> #syz dup: exact-subject-of-another-report
>
> If you want to undo deduplication, reply with:
> #syz undup

Hmm, I thought I already sent a patch for this issue, let me find it
in my trees.