syzbot


KCSAN: data-race in __anon_vma_prepare / handle_mm_fault (6)

Status: moderation: reported on 2026/04/25 15:15
Subsystems: mm
[Documentation on labels]
Reported-by: syzbot+fbdda2a8baef815acc22@syzkaller.appspotmail.com
First crash: 2d00h, last: 2d00h
✨ AI Jobs (1)
ID Workflow Result Correct Bug Created Started Finished Revision Error
6f64ae7a-235e-47a2-81f7-58ac00eddbb2 assessment-kcsan Benign: ✅  Confident: ✅  KCSAN: data-race in __anon_vma_prepare / handle_mm_fault (6) 2026/04/25 15:15 2026/04/25 15:15 2026/04/25 15:36 9c2d0995bb06e7518555bd3b755e327c89b59823
Similar bugs (5)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KCSAN: data-race in __anon_vma_prepare / handle_mm_fault (3) mm 6 5 623d 672d 0/29 auto-obsoleted due to no activity on 2024/09/15 23:12
upstream KCSAN: data-race in __anon_vma_prepare / handle_mm_fault (4) mm 6 3 500d 524d 0/29 auto-obsoleted due to no activity on 2025/02/07 03:27
upstream KCSAN: data-race in __anon_vma_prepare / handle_mm_fault (5) mm 6 16 61d 377d 0/29 auto-obsoleted due to no activity on 2026/04/22 02:48
upstream KCSAN: data-race in __anon_vma_prepare / handle_mm_fault (2) mm 6 123 730d 870d 0/29 auto-obsoleted due to no activity on 2024/05/31 23:05
upstream KCSAN: data-race in __anon_vma_prepare / handle_mm_fault mm 6 7 1717d 1797d 0/29 auto-closed as invalid on 2021/09/18 03:16

Sample crash report:
==================================================================
BUG: KCSAN: data-race in __anon_vma_prepare / handle_mm_fault

write to 0xffff888145dea040 of 8 bytes by task 8850 on cpu 0:
 __anon_vma_prepare+0x172/0x2f0 mm/rmap.c:212
 __vmf_anon_prepare mm/memory.c:3813 [inline]
 vmf_anon_prepare mm/internal.h:503 [inline]
 do_anonymous_page mm/memory.c:5372 [inline]
 do_pte_missing mm/memory.c:4548 [inline]
 handle_pte_fault mm/memory.c:6411 [inline]
 __handle_mm_fault mm/memory.c:6549 [inline]
 handle_mm_fault+0x24ae/0x2e70 mm/memory.c:6718
 do_user_addr_fault+0x3fd/0x1050 arch/x86/mm/fault.c:1385
 handle_page_fault arch/x86/mm/fault.c:1474 [inline]
 exc_page_fault+0x62/0xa0 arch/x86/mm/fault.c:1527
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618
 __put_user_4+0xd/0x20 arch/x86/lib/putuser.S:92
 __sys_socketpair+0xa6/0x420 net/socket.c:1856
 __do_sys_socketpair net/socket.c:1922 [inline]
 __se_sys_socketpair net/socket.c:1919 [inline]
 __x64_sys_socketpair+0x52/0x60 net/socket.c:1919
 x64_sys_call+0x2de5/0x3020 arch/x86/include/generated/asm/syscalls_64.h:54
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888145dea040 of 8 bytes by task 8849 on cpu 1:
 __vmf_anon_prepare mm/memory.c:3807 [inline]
 vmf_anon_prepare mm/internal.h:503 [inline]
 do_anonymous_page mm/memory.c:5372 [inline]
 do_pte_missing mm/memory.c:4548 [inline]
 handle_pte_fault mm/memory.c:6411 [inline]
 __handle_mm_fault mm/memory.c:6549 [inline]
 handle_mm_fault+0xff8/0x2e70 mm/memory.c:6718
 do_user_addr_fault+0x62f/0x1050 arch/x86/mm/fault.c:1334
 handle_page_fault arch/x86/mm/fault.c:1474 [inline]
 exc_page_fault+0x62/0xa0 arch/x86/mm/fault.c:1527
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618

value changed: 0x0000000000000000 -> 0xffff88811a2c8780

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 8849 Comm: syz.4.9406 Tainted: G        W           syzkaller #0 PREEMPT(full) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/04/25 15:14 upstream 27d128c1cff6 9c2d0995 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __anon_vma_prepare / handle_mm_fault
* Struck through repros no longer work on HEAD.