syzbot


KCSAN: data-race in __filemap_add_folio / sync_bdevs (3)

Status: moderation: reported on 2026/02/23 21:13
Subsystems: ext4
[Documentation on labels]
Reported-by: syzbot+40f776a7f1b5e8cb4f6c@syzkaller.appspotmail.com
First crash: 1d07h, last: 1d07h
✨ AI Jobs (1)
ID Workflow Result Correct Bug Created Started Finished Revision Error
af7922ee-8483-4d3c-aa57-4bcef35f1887 assessment-kcsan Benign: ✅  Confident: ✅  KCSAN: data-race in __filemap_add_folio / sync_bdevs (3) 2026/02/23 21:13 2026/02/23 21:13 2026/02/23 21:22 305c0ec5cd886e2d13738e28e1b2df9b0ec20fc9
Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KCSAN: data-race in __filemap_add_folio / sync_bdevs fs mm 6 1 1126d 1126d 0/29 auto-obsoleted due to no activity on 2023/04/05 16:41
upstream KCSAN: data-race in __filemap_add_folio / sync_bdevs (2) ext4 6 1 521d 521d 0/29 auto-obsoleted due to no activity on 2024/10/26 07:57

Sample crash report:
==================================================================
BUG: KCSAN: data-race in __filemap_add_folio / sync_bdevs

read-write to 0xffff88810066b138 of 8 bytes by task 2962 on cpu 1:
 __filemap_add_folio+0x671/0x8b0 mm/filemap.c:919
 filemap_add_folio+0x1d3/0x350 mm/filemap.c:966
 __filemap_get_folio_mpol+0x326/0x680 mm/filemap.c:2016
 __filemap_get_folio include/linux/pagemap.h:774 [inline]
 grow_dev_folio fs/buffer.c:1047 [inline]
 grow_buffers fs/buffer.c:1113 [inline]
 __getblk_slow fs/buffer.c:1131 [inline]
 bdev_getblk+0x173/0x3f0 fs/buffer.c:1458
 __getblk include/linux/buffer_head.h:380 [inline]
 jbd2_journal_get_descriptor_buffer+0xce/0x210 fs/jbd2/journal.c:976
 jbd2_journal_commit_transaction+0xcc8/0x3420 fs/jbd2/commit.c:610
 kjournald2+0x22e/0x3e0 fs/jbd2/journal.c:201
 kthread+0x22a/0x280 kernel/kthread.c:467
 ret_from_fork+0x150/0x360 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

read to 0xffff88810066b138 of 8 bytes by task 23265 on cpu 0:
 sync_bdevs+0xd3/0x260 block/bdev.c:1285
 ksys_sync fs/sync.c:106 [inline]
 __ia32_sys_sync+0x8b/0xb0 fs/sync.c:111
 x64_sys_call+0x2f3a/0x3020 arch/x86/include/generated/asm/syscalls_64.h:163
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x370 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000000383 -> 0x0000000000000384

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 23265 Comm: syz.5.6666 Tainted: G        W           syzkaller #0 PREEMPT(full) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/02/23 21:13 upstream 7dff99b35460 6beca497 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __filemap_add_folio / sync_bdevs
* Struck through repros no longer work on HEAD.