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KCSAN: data-race in mark_buffer_dirty_inode / mark_buffer_dirty_inode (13)

Status: moderation: reported on 2026/02/08 16:17
Subsystems: exfat
[Documentation on labels]
Reported-by: syzbot+c77c6c4a4e6c30fb8ea4@syzkaller.appspotmail.com
First crash: 50d, last: 50d
▶ ▼ ✨ AI Jobs (2)
ID Workflow Result Correct Bug Created Started Finished Revision Error
a0dddf99-baa4-4387-848a-c19361b44794 assessment-kcsan Benign: ✅  Confident: ✅  ❓ KCSAN: data-race in mark_buffer_dirty_inode / mark_buffer_dirty_inode (13) 2026/02/25 03:11 2026/02/25 03:11 2026/02/25 03:14 305c0ec5cd886e2d13738e28e1b2df9b0ec20fc9
86d8b352-ae47-4d46-8956-19de93d5edf7 assessment-kcsan 💥 KCSAN: data-race in mark_buffer_dirty_inode / mark_buffer_dirty_inode (13) 2026/02/08 16:17 2026/02/08 16:17 2026/02/08 16:17 97745f52f5b9361548048f53f0b3b51b9313fedf fork/exec ./syz-agent: no such file or directory
▶ ▼ Similar bugs (12)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KCSAN: data-race in mark_buffer_dirty_inode / mark_buffer_dirty_inode (5) exfat 6 5 1664d 1734d 0/29 auto-closed as invalid on 2021/10/13 19:55
upstream KCSAN: data-race in mark_buffer_dirty_inode / mark_buffer_dirty_inode (7) exfat 6 5 1323d 1358d 0/29 auto-closed as invalid on 2022/09/20 02:49
upstream KCSAN: data-race in mark_buffer_dirty_inode / mark_buffer_dirty_inode (2) exfat 6 11 1981d 2092d 0/29 auto-closed as invalid on 2020/11/30 13:39
upstream KCSAN: data-race in mark_buffer_dirty_inode / mark_buffer_dirty_inode (8) exfat 6 101 824d 844d 0/29 auto-obsoleted due to no activity on 2024/01/31 07:12
upstream KCSAN: data-race in mark_buffer_dirty_inode / mark_buffer_dirty_inode (3) exfat 6 2 1892d 1925d 0/29 auto-closed as invalid on 2021/02/27 21:17
upstream KCSAN: data-race in mark_buffer_dirty_inode / mark_buffer_dirty_inode (11) exfat 6 38 530d 660d 0/29 auto-obsoleted due to no activity on 2024/11/20 06:37
upstream KCSAN: data-race in mark_buffer_dirty_inode / mark_buffer_dirty_inode (10) exfat 6 1 716d 716d 0/29 auto-obsoleted due to no activity on 2024/05/18 09:53
upstream KCSAN: data-race in mark_buffer_dirty_inode / mark_buffer_dirty_inode (9) exfat 6 2 755d 771d 0/29 auto-obsoleted due to no activity on 2024/04/09 13:34
upstream KCSAN: data-race in mark_buffer_dirty_inode / mark_buffer_dirty_inode (6) exfat 6 6 1430d 1478d 0/29 auto-closed as invalid on 2022/06/04 23:25
upstream KCSAN: data-race in mark_buffer_dirty_inode / mark_buffer_dirty_inode exfat 6 1 2124d 2124d 0/29 closed as invalid on 2020/06/18 14:13
upstream KCSAN: data-race in mark_buffer_dirty_inode / mark_buffer_dirty_inode (4) exfat 6 8 1771d 1809d 0/29 auto-closed as invalid on 2021/06/28 13:09
upstream KCSAN: data-race in mark_buffer_dirty_inode / mark_buffer_dirty_inode (12) exfat 6 30 112d 493d 0/29 auto-obsoleted due to no activity on 2026/02/02 10:16

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

write to 0xffff88812c76fd58 of 8 bytes by task 5176 on cpu 0:
 mark_buffer_dirty_inode+0x18c/0x1c0 fs/buffer.c:693
 fat_mirror_bhs+0x234/0x320 fs/fat/fatent.c:398
 fat_alloc_clusters+0xb48/0xc50 fs/fat/fatent.c:543
 fat_add_cluster fs/fat/inode.c:108 [inline]
 __fat_get_block fs/fat/inode.c:155 [inline]
 fat_get_block+0x258/0x5e0 fs/fat/inode.c:190
 __block_write_begin_int+0x400/0xf90 fs/buffer.c:2145
 block_write_begin fs/buffer.c:2256 [inline]
 cont_write_begin+0x5fe/0x970 fs/buffer.c:2594
 fat_write_begin+0x4f/0xe0 fs/fat/inode.c:230
 generic_perform_write+0x183/0x490 mm/filemap.c:4314
 __generic_file_write_iter+0x9e/0x120 mm/filemap.c:4431
 generic_file_write_iter+0x8d/0x310 mm/filemap.c:4457
 new_sync_write fs/read_write.c:593 [inline]
 vfs_write+0x5a6/0x9f0 fs/read_write.c:686
 ksys_write+0xdc/0x1a0 fs/read_write.c:738
 __do_sys_write fs/read_write.c:749 [inline]
 __se_sys_write fs/read_write.c:746 [inline]
 __x64_sys_write+0x40/0x50 fs/read_write.c:746
 x64_sys_call+0x2847/0x3000 arch/x86/include/generated/asm/syscalls_64.h:2
 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 0xffff88812c76fd58 of 8 bytes by task 5179 on cpu 1:
 mark_buffer_dirty_inode+0x95/0x1c0 fs/buffer.c:689
 fat_mirror_bhs+0x234/0x320 fs/fat/fatent.c:398
 fat_alloc_clusters+0xb48/0xc50 fs/fat/fatent.c:543
 fat_add_cluster fs/fat/inode.c:108 [inline]
 __fat_get_block fs/fat/inode.c:155 [inline]
 fat_get_block+0x258/0x5e0 fs/fat/inode.c:190
 __block_write_begin_int+0x400/0xf90 fs/buffer.c:2145
 block_write_begin fs/buffer.c:2256 [inline]
 cont_write_begin+0x5fe/0x970 fs/buffer.c:2594
 fat_write_begin+0x4f/0xe0 fs/fat/inode.c:230
 generic_perform_write+0x183/0x490 mm/filemap.c:4314
 __generic_file_write_iter+0x9e/0x120 mm/filemap.c:4431
 generic_file_write_iter+0x8d/0x310 mm/filemap.c:4457
 aio_write+0x2fe/0x430 fs/aio.c:1634
 __io_submit_one fs/aio.c:-1 [inline]
 io_submit_one+0xbc1/0x1350 fs/aio.c:2053
 __do_sys_io_submit fs/aio.c:2112 [inline]
 __se_sys_io_submit+0xfb/0x280 fs/aio.c:2082
 __x64_sys_io_submit+0x43/0x50 fs/aio.c:2082
 x64_sys_call+0x2e40/0x3000 arch/x86/include/generated/asm/syscalls_64.h:210
 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

value changed: 0x0000000000000000 -> 0xffff88811a92a008

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 5179 Comm: syz.4.7392 Tainted: G        W           syzkaller #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/24/2026
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/02/08 16:17 upstream e7aa57247700 4c131dc4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in mark_buffer_dirty_inode / mark_buffer_dirty_inode
* Struck through repros no longer work on HEAD.