syzbot


KCSAN: data-race in fat16_ent_put / fat_mirror_bhs

Status: moderation: reported on 2025/04/25 15:47
Subsystems: exfat
[Documentation on labels]
Reported-by: syzbot+018e6f695ad9bccb182a@syzkaller.appspotmail.com
First crash: 299d, last: 13h19m

Sample crash report:
==================================================================
BUG: KCSAN: data-race in fat16_ent_put / fat_mirror_bhs

write to 0xffff88810b4275dc of 2 bytes by task 26301 on cpu 1:
 fat16_ent_put+0x28/0x60 fs/fat/fatent.c:183
 fat_alloc_clusters+0x57b/0xc50 fs/fat/fatent.c:503
 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:2143
 block_write_begin fs/buffer.c:2254 [inline]
 cont_write_begin+0x5fe/0x970 fs/buffer.c:2592
 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:595 [inline]
 vfs_write+0x5a6/0x9f0 fs/read_write.c:688
 ksys_write+0xdc/0x1a0 fs/read_write.c:740
 __do_sys_write fs/read_write.c:751 [inline]
 __se_sys_write fs/read_write.c:748 [inline]
 __x64_sys_write+0x40/0x50 fs/read_write.c:748
 x64_sys_call+0x27e1/0x3020 arch/x86/include/generated/asm/syscalls_64.h:2
 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

read to 0xffff88810b427400 of 512 bytes by task 26302 on cpu 0:
 fat_mirror_bhs+0x1df/0x320 fs/fat/fatent.c:395
 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:2143
 block_write_begin fs/buffer.c:2254 [inline]
 cont_write_begin+0x5fe/0x970 fs/buffer.c:2592
 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
 do_iter_readv_writev+0x4fd/0x5a0 fs/read_write.c:-1
 vfs_writev+0x2e1/0x900 fs/read_write.c:1059
 do_pwritev fs/read_write.c:1155 [inline]
 __do_sys_pwritev2 fs/read_write.c:1213 [inline]
 __se_sys_pwritev2+0xfc/0x1c0 fs/read_write.c:1204
 __x64_sys_pwritev2+0x67/0x80 fs/read_write.c:1204
 x64_sys_call+0xe07/0x3020 arch/x86/include/generated/asm/syscalls_64.h:329
 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

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 26302 Comm: syz.4.7730 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 (669):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/02/18 10:21 upstream 2961f841b025 39751c21 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in fat16_ent_put / fat_mirror_bhs
2026/02/18 01:36 upstream d295082ea672 06ec4f7b .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in fat16_ent_put / fat_mirror_bhs
2026/02/17 07:48 upstream 970296997869 e439b951 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in fat16_ent_put / fat_mirror_bhs
2026/02/16 17:14 upstream 0f2acd3148e0 5d52cba5 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in fat16_ent_put / fat_mirror_bhs
2026/02/16 00:56 upstream 26a4cfaff82a 1e62d198 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in fat16_ent_put / fat_mirror_bhs
2026/02/15 10:57 upstream ca4ee40bf13d 1e62d198 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in fat16_ent_put / fat_mirror_bhs
2026/02/15 10:54 upstream ca4ee40bf13d 1e62d198 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in fat16_ent_put / fat_mirror_bhs
2026/02/14 21:42 upstream 3e48a11675c5 1e62d198 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in fat16_ent_put / fat_mirror_bhs
2026/02/14 14:08 upstream 770aaedb461a 1e62d198 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in fat16_ent_put / fat_mirror_bhs
2026/02/13 20:35 upstream cee73b1e840c 1e62d198 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in fat16_ent_put / fat_mirror_bhs
2026/02/13 11:12 upstream 37a93dd5c49b 6a673c50 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in fat16_ent_put / fat_mirror_bhs
2026/02/13 01:30 upstream 37a93dd5c49b 504cb1bf .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in fat16_ent_put / fat_mirror_bhs
2026/02/10 20:57 upstream 72c395024dac 91d776d3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in fat16_ent_put / fat_mirror_bhs
2026/02/10 03:36 upstream 8a5203c630c6 4ab09a02 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in fat16_ent_put / fat_mirror_bhs
2026/02/09 20:43 upstream 05f7e89ab973 df949cd9 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in fat16_ent_put / fat_mirror_bhs
2026/02/08 16:15 upstream e7aa57247700 4c131dc4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in fat16_ent_put / fat_mirror_bhs
2026/02/07 03:04 upstream 2687c848e578 f20fc9f9 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in fat16_ent_put / fat_mirror_bhs
2026/02/06 14:03 upstream b7ff7151e653 97745f52 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in fat16_ent_put / fat_mirror_bhs
2026/02/05 22:24 upstream 8fdb05de0e2d f03c4191 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in fat16_ent_put / fat_mirror_bhs
2026/02/05 18:55 upstream 8fdb05de0e2d 4936e85c .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in fat16_ent_put / fat_mirror_bhs
2026/02/05 09:57 upstream f14faaf3a1fb 4936e85c .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in fat16_ent_put / fat_mirror_bhs
2026/02/04 17:24 upstream 5fd0a1df5d05 ea10c935 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in fat16_ent_put / fat_mirror_bhs
2026/02/04 00:10 upstream de0674d9bc69 42b01fab .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in fat16_ent_put / fat_mirror_bhs
2026/02/03 21:07 upstream 6bd9ed02871f 6df4c87a .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in fat16_ent_put / fat_mirror_bhs
2026/02/02 22:45 upstream dee65f79364c d78927dd .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in fat16_ent_put / fat_mirror_bhs
2026/02/02 10:17 upstream 18f7fcd5e69a 018ebef2 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in fat16_ent_put / fat_mirror_bhs
2026/02/01 21:20 upstream 9f2693489ef8 6b8752f2 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in fat16_ent_put / fat_mirror_bhs
2026/02/01 02:33 upstream ad9a728a3388 6b8752f2 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in fat16_ent_put / fat_mirror_bhs
2026/01/31 19:09 upstream ad9a728a3388 afc0c4d4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in fat16_ent_put / fat_mirror_bhs
2026/01/31 02:42 upstream 283073725700 c75a2f6e .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in fat16_ent_put / fat_mirror_bhs
2026/01/31 00:53 upstream 4d310797262f c75a2f6e .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in fat16_ent_put / fat_mirror_bhs
2026/01/30 13:50 upstream 4d310797262f ae7dc18c .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in fat16_ent_put / fat_mirror_bhs
2026/01/30 10:22 upstream 4d310797262f bfa73b7b .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in fat16_ent_put / fat_mirror_bhs
2026/01/29 11:33 upstream 8dfce8991b95 aeb6fdd5 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in fat16_ent_put / fat_mirror_bhs
2026/01/29 05:36 upstream 8dfce8991b95 0adc945e .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in fat16_ent_put / fat_mirror_bhs
2026/01/28 18:15 upstream 8dfce8991b95 004c195c .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in fat16_ent_put / fat_mirror_bhs
2026/01/28 11:15 upstream 1f97d9dcf536 004c195c .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in fat16_ent_put / fat_mirror_bhs
2026/01/27 23:31 upstream 1f97d9dcf536 3029c699 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in fat16_ent_put / fat_mirror_bhs
2026/01/27 15:29 upstream fcb70a56f4d8 9a514c2f .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in fat16_ent_put / fat_mirror_bhs
2026/01/27 00:28 upstream fcb70a56f4d8 efb3e894 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in fat16_ent_put / fat_mirror_bhs
2026/01/26 14:43 upstream 63804fed149a a4c52dd6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in fat16_ent_put / fat_mirror_bhs
2026/01/26 01:07 upstream 023777797472 55756628 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in fat16_ent_put / fat_mirror_bhs
2026/01/25 17:51 upstream d91a46d6805a 40acda8a .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in fat16_ent_put / fat_mirror_bhs
2026/01/25 02:24 upstream 5dbeeb268b63 40acda8a .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in fat16_ent_put / fat_mirror_bhs
2026/01/24 12:50 upstream 62085877ae65 40acda8a .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in fat16_ent_put / fat_mirror_bhs
2026/01/23 10:15 upstream c072629f05d7 e2b1b6e6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in fat16_ent_put / fat_mirror_bhs
2026/01/23 09:06 upstream c072629f05d7 82c9c083 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in fat16_ent_put / fat_mirror_bhs
2026/01/10 02:38 upstream 372800cb95a3 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in fat16_ent_put / fat_mirror_bhs
2025/04/25 15:47 upstream 02ddfb981de8 e3715315 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in fat16_ent_put / fat_mirror_bhs
* Struck through repros no longer work on HEAD.