syzbot


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

Status: moderation: reported on 2025/10/19 01:27
Subsystems: mm
[Documentation on labels]
Reported-by: syzbot+e28bd6fd306dd4ff1468@syzkaller.appspotmail.com
First crash: 3d07h, last: 2d02h
Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KCSAN: data-race in _copy_to_iter / copy_folio_from_iter_atomic mm 6 2 80d 132d 0/29 auto-obsoleted due to no activity on 2025/09/28 04:36

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

write to 0xffff88813af497a2 of 92 bytes by task 14170 on cpu 0:
 memcpy_from_iter lib/iov_iter.c:73 [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:249 [inline]
 copy_folio_from_iter_atomic+0x7fc/0x11b0 lib/iov_iter.c:479
 generic_perform_write+0x2c2/0x490 mm/filemap.c:4260
 shmem_file_write_iter+0xc5/0xf0 mm/shmem.c:3464
 iter_file_splice_write+0x666/0xa60 fs/splice.c:738
 do_splice_from fs/splice.c:938 [inline]
 direct_splice_actor+0x156/0x2a0 fs/splice.c:1161
 splice_direct_to_actor+0x312/0x680 fs/splice.c:1105
 do_splice_direct_actor fs/splice.c:1204 [inline]
 do_splice_direct+0xda/0x150 fs/splice.c:1230
 do_sendfile+0x380/0x650 fs/read_write.c:1370
 __do_sys_sendfile64 fs/read_write.c:1431 [inline]
 __se_sys_sendfile64 fs/read_write.c:1417 [inline]
 __x64_sys_sendfile64+0x105/0x150 fs/read_write.c:1417
 x64_sys_call+0x2bb4/0x3000 arch/x86/include/generated/asm/syscalls_64.h:41
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88813af497a2 of 46 bytes by task 14168 on cpu 1:
 memcpy_to_iter lib/iov_iter.c:65 [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_to_iter+0x602/0xe70 lib/iov_iter.c:185
 copy_page_to_iter+0x18f/0x2d0 lib/iov_iter.c:362
 copy_folio_to_iter include/linux/uio.h:204 [inline]
 shmem_file_read_iter+0x2d6/0x540 mm/shmem.c:3412
 copy_splice_read+0x442/0x660 fs/splice.c:363
 do_splice_read fs/splice.c:981 [inline]
 splice_direct_to_actor+0x290/0x680 fs/splice.c:1086
 do_splice_direct_actor fs/splice.c:1204 [inline]
 do_splice_direct+0xda/0x150 fs/splice.c:1230
 do_sendfile+0x380/0x650 fs/read_write.c:1370
 __do_sys_sendfile64 fs/read_write.c:1431 [inline]
 __se_sys_sendfile64 fs/read_write.c:1417 [inline]
 __x64_sys_sendfile64+0x105/0x150 fs/read_write.c:1417
 x64_sys_call+0x2bb4/0x3000 arch/x86/include/generated/asm/syscalls_64.h:41
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 14168 Comm: syz.4.3052 Tainted: G        W           syzkaller #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
==================================================================

Crashes (4):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/10/20 06:53 upstream 211ddde0823f 1c8c8cd8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in _copy_to_iter / copy_folio_from_iter_atomic
2025/10/20 06:52 upstream 211ddde0823f 1c8c8cd8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in _copy_to_iter / copy_folio_from_iter_atomic
2025/10/20 06:52 upstream 211ddde0823f 1c8c8cd8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in _copy_to_iter / copy_folio_from_iter_atomic
2025/10/19 01:26 upstream 1c64efcb083c 1c8c8cd8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in _copy_to_iter / copy_folio_from_iter_atomic
* Struck through repros no longer work on HEAD.