[moderation] [kernel?] KCSAN: data-race in prepare_signal / ptrace_attach (11)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 20cb38a7af88 Merge tag 'for-6.9-rc2-tag' of git://git.kern..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11fe4f8d180000
kernel config: https://syzkaller.appspot.com/x/.config?x=ae557ecb5cabc4aa
dashboard link: https://syzkaller.appspot.com/bug?extid=142d9ec803fd1b652b28
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
CC: [linux-...@vger.kernel.org ol...@redhat.com]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/1c92ddc37dc2/disk-20cb38a7.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/2f582de438c0/vmlinux-20cb38a7.xz
kernel image: https://storage.googleapis.com/syzbot-assets/c35d06026809/bzImage-20cb38a7.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+142d9e...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in prepare_signal / ptrace_attach

write to 0xffff888150222130 of 4 bytes by task 23853 on cpu 0:
ptrace_attach+0x321/0x590 kernel/ptrace.c:462
__do_sys_ptrace kernel/ptrace.c:1276 [inline]
__se_sys_ptrace+0x149/0x2b0 kernel/ptrace.c:1258
__x64_sys_ptrace+0x55/0x70 kernel/ptrace.c:1258
do_syscall_64+0xd3/0x1d0
entry_SYSCALL_64_after_hwframe+0x72/0x7a

read to 0xffff888150222130 of 4 bytes by task 23848 on cpu 1:
prepare_signal+0x258/0x670 kernel/signal.c:934
__send_signal_locked+0x2f/0x700 kernel/signal.c:1085
send_signal_locked+0x28f/0x3a0 kernel/signal.c:1248
do_send_sig_info+0x9f/0xf0 kernel/signal.c:1301
group_send_sig_info kernel/signal.c:1453 [inline]
kill_pid_info_type+0x85/0xd0 kernel/signal.c:1493
kill_pid_info kernel/signal.c:1507 [inline]
kill_proc_info kernel/signal.c:1514 [inline]
do_rt_sigqueueinfo kernel/signal.c:4063 [inline]
__do_sys_rt_sigqueueinfo kernel/signal.c:4079 [inline]
__se_sys_rt_sigqueueinfo+0xcd/0x110 kernel/signal.c:4072
__x64_sys_rt_sigqueueinfo+0x43/0x50 kernel/signal.c:4072
do_syscall_64+0xd3/0x1d0
entry_SYSCALL_64_after_hwframe+0x72/0x7a

value changed: 0x00000000 -> 0x00000001

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 23848 Comm: syz-executor.2 Tainted: G W 6.9.0-rc3-syzkaller-00011-g20cb38a7af88 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
==================================================================


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