[moderation] [kernel?] KCSAN: data-race in prepare_signal / ptrace_attach (13)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: c62f4b82d571 Merge tag 'v6.15-p4' of git://git.kernel.org/..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12434204580000
kernel config: https://syzkaller.appspot.com/x/.config?x=f723126dfc2a8a53
dashboard link: https://syzkaller.appspot.com/bug?extid=f95a52b1bb9c1a00dd0c
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/b882e6d2280a/disk-c62f4b82.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/389bb377e299/vmlinux-c62f4b82.xz
kernel image: https://storage.googleapis.com/syzbot-assets/1f01e442cd4e/bzImage-c62f4b82.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+f95a52...@syzkaller.appspotmail.com

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

write to 0xffff88810af24230 of 4 bytes by task 23226 on cpu 0:
ptrace_attach+0x258/0x520 kernel/ptrace.c:462
__do_sys_ptrace kernel/ptrace.c:1276 [inline]
__se_sys_ptrace+0x14c/0x2b0 kernel/ptrace.c:1258
__x64_sys_ptrace+0x55/0x70 kernel/ptrace.c:1258
x64_sys_call+0x1fd0/0x2e10 arch/x86/include/generated/asm/syscalls_64.h:102
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xc9/0x1c0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88810af24230 of 4 bytes by task 23227 on cpu 1:
sig_ignored kernel/signal.c:121 [inline]
prepare_signal+0x45d/0x670 kernel/signal.c:935
__send_signal_locked+0x31/0x7a0 kernel/signal.c:1053
send_signal_locked+0x28f/0x3a0 kernel/signal.c:1216
force_sig_info_to_task+0x1ef/0x280 kernel/signal.c:1320
force_sig_fault_to_task kernel/signal.c:1699 [inline]
force_sig_fault+0x79/0xa0 kernel/signal.c:1704
__bad_area_nosemaphore+0x261/0x320 arch/x86/mm/fault.c:824
handle_page_fault arch/x86/mm/fault.c:1478 [inline]
exc_page_fault+0x4e1/0x6a0 arch/x86/mm/fault.c:1538
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623

value changed: 0x00000000 -> 0x00000001

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 23227 Comm: syz.0.6759 Not tainted 6.15.0-rc2-syzkaller-00048-gc62f4b82d571 #0 PREEMPT(voluntary)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
==================================================================


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[syzbot]

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