KCSAN: data-race in copy_process / show_stat (6)

Status: moderation: reported on 2026/08/29 21:50
Subsystems: mm
Labels: race:benign
[Documentation on labels]
Reported-by: syzbot+99adfb9c044104c58db8@syzkaller.appspotmail.com
First crash: 1d02h, last: 1d02h
▶ ▼ ✨ AI Jobs (1)
ID Workflow Result Correct Bug Created Started Finished Revision
f6c61e5f assessment-kcsan Benign: ✅ ❓ KCSAN: data-race in copy_process / show_stat (6) 2026/08/29 21:49 2026/08/29 21:50 2026/08/29 22:18 2f52988a
▶ ▼ Similar bugs (5)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KCSAN: data-race in copy_process / show_stat (2) mm 6 2 2136d 2139d 0/29 auto-closed as invalid on 2020/11/28 01:56
upstream KCSAN: data-race in copy_process / show_stat (3) mm 6 1 1529d 1529d 0/29 auto-closed as invalid on 2022/07/28 00:27
upstream KCSAN: data-race in copy_process / show_stat mm 6 3 2174d 2212d 0/29 auto-closed as invalid on 2020/10/21 12:32
upstream KCSAN: data-race in copy_process / show_stat (4) mm 6 1 1287d 1287d 0/29 auto-obsoleted due to no activity on 2023/04/17 12:00
upstream KCSAN: data-race in copy_process / show_stat (5) race:benign prio:low mm 6 1 93d 93d 0/29 auto-obsoleted due to no activity on 2026/07/24 14:53

Sample crash report:
==================================================================
BUG: KCSAN: data-race in copy_process / show_stat

read-write to 0xffffffff895a8ad8 of 8 bytes by task 10039 on cpu 0:
 copy_process+0x21bb/0x2340 kernel/fork.c:2554
 kernel_clone+0x1c0/0x5f0 kernel/fork.c:2766
 __do_sys_clone kernel/fork.c:2908 [inline]
 __se_sys_clone kernel/fork.c:2892 [inline]
 __x64_sys_clone+0x143/0x180 kernel/fork.c:2892
 x64_sys_call+0x2479/0x2550 arch/x86/include/generated/asm/syscalls_64.h:57
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x112/0x360 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff895a8ad8 of 8 bytes by task 27227 on cpu 1:
 show_stat+0xa27/0xb90 fs/proc/stat.c:145
 seq_read_iter+0x2d9/0x8f0 fs/seq_file.c:231
 proc_reg_read_iter+0xe6/0x180 fs/proc/inode.c:295
 copy_splice_read+0x47a/0x6b0 fs/splice.c:362
 do_splice_read fs/splice.c:980 [inline]
 splice_direct_to_actor+0x261/0x680 fs/splice.c:1084
 do_splice_direct_actor fs/splice.c:1202 [inline]
 do_splice_direct+0x119/0x1a0 fs/splice.c:1228
 do_sendfile+0x37d/0x640 fs/read_write.c:1371
 __do_sys_sendfile64 fs/read_write.c:1432 [inline]
 __se_sys_sendfile64 fs/read_write.c:1418 [inline]
 __x64_sys_sendfile64+0x105/0x150 fs/read_write.c:1418
 x64_sys_call+0x1015/0x2550 arch/x86/include/generated/asm/syscalls_64.h:41
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x112/0x360 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000006a3d -> 0x0000000000006a3e

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 27227 Comm: syz.8.7489 Not tainted syzkaller #0 PREEMPT(lazy) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/29 21:49 upstream 08dbfad3f504 2f52988a .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in copy_process / show_stat
* Struck through repros no longer work on HEAD.