KCSAN: data-race in audit_log_start / skb_queue_tail

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: a1b8638b Linux 5.9-rc7
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=159890a7900000
kernel config: https://syzkaller.appspot.com/x/.config?x=d3bb4312bebb1dd3
dashboard link: https://syzkaller.appspot.com/bug?extid=93408477dcf4f9919bef
compiler: clang version 11.0.0 (https://github.com/llvm/llvm-project.git ca2dcbd030eadbf0aa9b660efe864ff08af6e18b)
CC: [epa...@redhat.com linux...@redhat.com linux-...@vger.kernel.org pa...@paul-moore.com]

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

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+934084...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in audit_log_start / skb_queue_tail

write to 0xffffffff89519150 of 4 bytes by task 19288 on cpu 0:
__skb_insert include/linux/skbuff.h:1911 [inline]
__skb_queue_before include/linux/skbuff.h:2016 [inline]
__skb_queue_tail include/linux/skbuff.h:2049 [inline]
skb_queue_tail+0x80/0xa0 net/core/skbuff.c:3146
audit_log_end+0x171/0x1e0 kernel/audit.c:2387
audit_seccomp+0x108/0x120 kernel/auditsc.c:2680
seccomp_log kernel/seccomp.c:767 [inline]
__seccomp_filter+0xc87/0xe90 kernel/seccomp.c:1042
__secure_computing+0x12e/0x1c0 kernel/seccomp.c:1070
syscall_trace_enter+0x10f/0x2c0 kernel/entry/common.c:58
__syscall_enter_from_user_work kernel/entry/common.c:81 [inline]
syscall_enter_from_user_mode+0x2a/0x40 kernel/entry/common.c:99
do_syscall_64+0x11/0x80 arch/x86/entry/common.c:41
entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffffffff89519150 of 4 bytes by task 19298 on cpu 1:
skb_queue_len include/linux/skbuff.h:1842 [inline]
audit_log_start+0x18c/0x6a0 kernel/audit.c:1834
audit_seccomp+0x47/0x120 kernel/auditsc.c:2673
seccomp_log kernel/seccomp.c:767 [inline]
__seccomp_filter+0xc87/0xe90 kernel/seccomp.c:1042
__secure_computing+0x12e/0x1c0 kernel/seccomp.c:1070
syscall_trace_enter+0x10f/0x2c0 kernel/entry/common.c:58
__syscall_enter_from_user_work kernel/entry/common.c:81 [inline]
syscall_enter_from_user_mode+0x2a/0x40 kernel/entry/common.c:99
do_syscall_64+0x11/0x80 arch/x86/entry/common.c:41
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 19298 Comm: *:* ���@�S�~Պ Not tainted 5.9.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.