syzbot


KCSAN: data-race in __fat_write_inode / copy_folio_from_iter_atomic (2)

Status: moderation: reported on 2025/10/02 01:11
Subsystems: exfat
[Documentation on labels]
Reported-by: syzbot+46fcf86d675442061f44@syzkaller.appspotmail.com
First crash: 168d, last: 10d
✨ AI Jobs (3)
ID Workflow Result Correct Bug Created Started Finished Revision Error
d1c15ed9-8247-40d3-872a-d1ccbd3b18a6 repro KCSAN: data-race in __fat_write_inode / copy_folio_from_iter_atomic (2) 2026/03/08 00:45 2026/03/08 00:45 2026/03/08 00:52 31e9c887f7dc24e04b3ca70d0d54fc34141844b0
537ae63a-cb65-4bc0-90ee-88b43d667145 assessment-kcsan Benign: ✅  Confident: ✅  KCSAN: data-race in __fat_write_inode / copy_folio_from_iter_atomic (2) 2026/02/24 21:20 2026/02/24 21:20 2026/02/24 21:31 305c0ec5cd886e2d13738e28e1b2df9b0ec20fc9
756567b6-1d74-444f-a1cd-4602748fc355 assessment-kcsan 💥 KCSAN: data-race in __fat_write_inode / copy_folio_from_iter_atomic (2) 2026/01/10 03:33 2026/01/10 03:33 2026/01/10 03:33 7519916073b761ced56a7b15fdeeb4674e8dc125 Error 429, Message: You exceeded your current quota, please check your plan and billing details. For more information on this error, head to: https://ai.google.dev/gemini-api/docs/rate-limits. To monitor your current usage, head to: https://ai.dev/rate-limit. * Quota exceeded for metric: generativelanguage.googleapis.com/generate_requests_per_model_per_day, limit: 0, Status: RESOURCE_EXHAUSTED, Details: [map[@type:type.googleapis.com/google.rpc.Help links:[map[description:Learn more about Gemini API quotas url:https://ai.google.dev/gemini-api/docs/rate-limits]]] map[@type:type.googleapis.com/google.rpc.QuotaFailure violations:[map[quotaId:GenerateRequestsPerDayPerProjectPerModel quotaMetric:generativelanguage.googleapis.com/generate_requests_per_model_per_day]]] map[@type:type.googleapis.com/google.rpc.DebugInfo detail:[ORIGINAL ERROR] generic::resource_exhausted: You exceeded your current quota, please check your plan and billing details. For more information on this error, head to: https://ai.google.dev/gemini-api/docs/rate-limits. To monitor your current usage, head to: https://ai.dev/rate-limit. * Quota exceeded for metric: generativelanguage.googleapis.com/generate_requests_per_model_per_day, limit: 0 [google.rpc.error_details_ext] { message: "You exceeded your current quota, please check your plan and billing details. For more information on this error, head to: https://ai.google.dev/gemini-api/docs/rate-limits. To monitor your current usage, head to: https://ai.dev/rate-limit. \n* Quota exceeded for metric: generativelanguage.googleapis.com/generate_requests_per_model_per_day, limit: 0" details { type_url: "type.googleapis.com/language_labs.genai.debug.GeminiApiDebugInfo" value: "RM\nK\nEgenerativelanguage.googleapis.com/generate_requests_per_model_per_day\030\000\"\000" } details { [type.googleapis.com/google.rpc.Help] { links { description: "Learn more about Gemini API quotas" url: "https://ai.google.dev/gemini-api/docs/rate-limits" } } } details { [type.googleapis.com/google.rpc.QuotaFailure] { violations { quota_metric: "generativelanguage.googleapis.com/generate_requests_per_model_per_day" quota_id: "GenerateRequestsPerDayPerProjectPerModel" } } } }]]
Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KCSAN: data-race in __fat_write_inode / copy_folio_from_iter_atomic exfat 6 1 227d 227d 0/29 auto-obsoleted due to no activity on 2025/09/28 22:16

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

write to 0xffff88813f3e7c1c of 4 bytes by task 20801 on cpu 0:
 __fat_write_inode+0x236/0x530 fs/fat/inode.c:-1
 fat_sync_inode+0x1a/0x30 fs/fat/inode.c:932
 fat_free fs/fat/file.c:333 [inline]
 fat_truncate_blocks+0x1cc/0x5a0 fs/fat/file.c:395
 fat_write_failed fs/fat/inode.c:219 [inline]
 fat_write_end+0xba/0x160 fs/fat/inode.c:247
 generic_perform_write+0x311/0x490 mm/filemap.c:4340
 __generic_file_write_iter+0x9e/0x120 mm/filemap.c:4436
 generic_file_write_iter+0x8d/0x310 mm/filemap.c:4462
 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 0xffff88813f3e7c00 of 1024 bytes by task 8835 on cpu 1:
 memcpy_from_iter lib/iov_iter.c:85 [inline]
 iterate_bvec include/linux/iov_iter.h:123 [inline]
 iterate_and_advance2 include/linux/iov_iter.h:306 [inline]
 iterate_and_advance include/linux/iov_iter.h:330 [inline]
 __copy_from_iter lib/iov_iter.c:261 [inline]
 copy_folio_from_iter_atomic+0x75f/0x1170 lib/iov_iter.c:491
 generic_perform_write+0x2c1/0x490 mm/filemap.c:4337
 shmem_file_write_iter+0xc5/0xf0 mm/shmem.c:3502
 lo_rw_aio+0x67d/0x730 drivers/block/loop.c:-1
 do_req_filebacked drivers/block/loop.c:-1 [inline]
 loop_handle_cmd drivers/block/loop.c:1925 [inline]
 loop_process_work+0x56c/0xac0 drivers/block/loop.c:1960
 loop_workfn+0x31/0x40 drivers/block/loop.c:1984
 process_one_work kernel/workqueue.c:3275 [inline]
 process_scheduled_works+0x4de/0x9e0 kernel/workqueue.c:3358
 worker_thread+0x581/0x770 kernel/workqueue.c:3439
 kthread+0x22a/0x280 kernel/kthread.c:436
 ret_from_fork+0x150/0x360 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 8835 Comm: kworker/u8:18 Tainted: G        W           syzkaller #0 PREEMPT(full) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Workqueue: loop5 loop_workfn
==================================================================

Crashes (9):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/03/08 21:43 upstream 014441d1e4b2 5cb44a80 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __fat_write_inode / copy_folio_from_iter_atomic
2026/02/04 12:18 upstream 5fd0a1df5d05 42b01fab .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __fat_write_inode / copy_folio_from_iter_atomic
2026/01/30 01:37 upstream 4d310797262f bfa73b7b .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __fat_write_inode / copy_folio_from_iter_atomic
2026/01/22 18:17 upstream a66191c590b3 82c9c083 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __fat_write_inode / copy_folio_from_iter_atomic
2026/01/19 05:40 upstream 24d479d26b25 20d37d28 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __fat_write_inode / copy_folio_from_iter_atomic
2025/12/10 20:53 upstream 0048fbb4011e d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __fat_write_inode / copy_folio_from_iter_atomic
2025/11/15 08:32 upstream 7a0892d2836e f7988ea4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __fat_write_inode / copy_folio_from_iter_atomic
2025/10/15 16:42 upstream 1f4a222b0e33 19568248 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __fat_write_inode / copy_folio_from_iter_atomic
2025/10/02 01:10 upstream 080ffb4bec4d 267f56c6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __fat_write_inode / copy_folio_from_iter_atomic
* Struck through repros no longer work on HEAD.