syzbot


KCSAN: data-race in copy_mm / copy_page_range (3)

Status: moderation: reported on 2025/11/07 06:03
Subsystems: mm
[Documentation on labels]
Reported-by: syzbot+5171c42274384b4a4dab@syzkaller.appspotmail.com
First crash: 102d, last: 31d
Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KCSAN: data-race in copy_mm / copy_page_range mm 6 3 240d 295d 0/29 auto-obsoleted due to no activity on 2025/08/17 07:05
upstream KCSAN: data-race in copy_mm / copy_page_range (2) mm 6 1 163d 163d 0/29 auto-obsoleted due to no activity on 2025/11/03 02:56

Sample crash report:
==================================================================
BUG: KCSAN: data-race in copy_mm / copy_page_range

read-write to 0xffff88811b592af8 of 4 bytes by task 14312 on cpu 1:
 do_raw_write_seqcount_begin include/linux/seqlock.h:431 [inline]
 copy_page_range+0x299/0x3d30 mm/memory.c:1525
 dup_mmap+0x852/0xf00 mm/mmap.c:1827
 dup_mm kernel/fork.c:1529 [inline]
 copy_mm+0x119/0x370 kernel/fork.c:1581
 copy_process+0xcbd/0x1f10 kernel/fork.c:2221
 kernel_clone+0x16b/0x5b0 kernel/fork.c:2651
 __do_sys_clone kernel/fork.c:2792 [inline]
 __se_sys_clone kernel/fork.c:2776 [inline]
 __x64_sys_clone+0x143/0x180 kernel/fork.c:2776
 x64_sys_call+0x12d0/0x3000 arch/x86/include/generated/asm/syscalls_64.h:57
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc0/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88811b592880 of 1664 bytes by task 14313 on cpu 0:
 dup_mm kernel/fork.c:1523 [inline]
 copy_mm+0xe1/0x370 kernel/fork.c:1581
 copy_process+0xcbd/0x1f10 kernel/fork.c:2221
 kernel_clone+0x16b/0x5b0 kernel/fork.c:2651
 __do_sys_clone kernel/fork.c:2792 [inline]
 __se_sys_clone kernel/fork.c:2776 [inline]
 __x64_sys_clone+0x143/0x180 kernel/fork.c:2776
 x64_sys_call+0x12d0/0x3000 arch/x86/include/generated/asm/syscalls_64.h:57
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc0/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 14313 Comm: syz.5.3608 Not tainted syzkaller #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
==================================================================

Crashes (6):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/01/17 05:27 upstream b62ce2547fe8 20d37d28 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in copy_mm / copy_page_range
2025/11/30 15:17 upstream 6bda50f4333f d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in copy_mm / copy_page_range
2025/11/20 06:49 upstream 23cb64fb7625 26ee5237 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in copy_mm / copy_page_range
2025/11/19 03:31 upstream 5bebe8de1926 ef766cd7 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in copy_mm / copy_page_range
2025/11/18 09:34 upstream e7c375b18160 ef766cd7 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in copy_mm / copy_page_range
2025/11/07 06:02 upstream c2c2ccfd4ba7 4e1406b4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in copy_mm / copy_page_range
* Struck through repros no longer work on HEAD.