KCSAN: data-race in do_sendfile / do_sendfile (11)

Status: moderation: reported C repro on 2026/10/11 11:37
Labels: prio:high race:benign
[Documentation on labels]
Reported-by: syzbot+399510418a0b0cf1fc29@syzkaller.appspotmail.com
First crash: 8h53m, last: 8h53m
▶ ▼ ✨ AI Jobs (2)
ID Workflow Result Correct Bug Created Started Finished Revision
c488d855 assessment-kcsan Benign: ✅ ❓ KCSAN: data-race in do_sendfile / do_sendfile (11) 2026/10/11 11:37 2026/10/11 11:37 2026/10/11 12:26 4f92358f
2a993ab1 assessment-security DenialOfService: ❌ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ✅ UserNamespace: ✅ VMGuestTrigger: ✅ VMHostTrigger: ❌ ❓ KCSAN: data-race in do_sendfile / do_sendfile (11) 2026/10/11 11:37 2026/10/11 11:37 2026/10/11 12:20 4f92358f
▶ ▼ Similar bugs (10)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KCSAN: data-race in do_sendfile / do_sendfile (3) fs 6 1 1373d 1373d 0/29 auto-obsoleted due to no activity on 2023/03/17 22:50
upstream KCSAN: data-race in do_sendfile / do_sendfile (4) fs 6 4 1262d 1285d 0/29 auto-obsoleted due to no activity on 2023/06/02 10:13
upstream KCSAN: data-race in do_sendfile / do_sendfile fs 6 2 1697d 1712d 0/29 auto-closed as invalid on 2022/03/24 16:27
upstream KCSAN: data-race in do_sendfile / do_sendfile (9) fs 6 1 756d 756d 0/29 auto-obsoleted due to no activity on 2024/10/20 07:46
upstream KCSAN: data-race in do_sendfile / do_sendfile (7) fs 6 5 987d 1035d 0/29 auto-obsoleted due to no activity on 2024/03/03 18:17
upstream KCSAN: data-race in do_sendfile / do_sendfile (6) fs 6 1 1132d 1132d 0/29 auto-obsoleted due to no activity on 2023/10/10 12:26
upstream KCSAN: data-race in do_sendfile / do_sendfile (10) fs 6 26 280d 697d 0/29 auto-obsoleted due to no activity on 2026/03/01 02:25
upstream KCSAN: data-race in do_sendfile / do_sendfile (5) fs 6 3 1173d 1194d 0/29 auto-obsoleted due to no activity on 2023/08/30 17:21
upstream KCSAN: data-race in do_sendfile / do_sendfile (8) fs 6 2 811d 835d 0/29 auto-obsoleted due to no activity on 2024/08/25 22:44
upstream KCSAN: data-race in do_sendfile / do_sendfile (2) fs 6 1 1512d 1512d 0/29 auto-closed as invalid on 2022/09/24 23:59

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

write to 0xffff888100ab77e8 of 8 bytes by task 3657 on cpu 0:
 do_sendfile+0x44c/0x640 fs/read_write.c:1389
 __do_sys_sendfile64 fs/read_write.c:1432 [inline]
 __se_sys_sendfile64 fs/read_write.c:1418 [inline]
 __x64_sys_sendfile64+0x105/0x150 fs/read_write.c:1418
 x64_sys_call+0x1015/0x2550 arch/x86/include/generated/asm/syscalls_64.h:41
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x112/0x360 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888100ab77e8 of 8 bytes by task 3658 on cpu 1:
 do_sendfile+0x116/0x640 fs/read_write.c:1322
 __do_sys_sendfile64 fs/read_write.c:1432 [inline]
 __se_sys_sendfile64 fs/read_write.c:1418 [inline]
 __x64_sys_sendfile64+0x105/0x150 fs/read_write.c:1418
 x64_sys_call+0x1015/0x2550 arch/x86/include/generated/asm/syscalls_64.h:41
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x112/0x360 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000004000 -> 0x0000000000008000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3658 Comm: syz-executor185 Not tainted syzkaller #0 PREEMPT(lazy) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
==================================================================
==================================================================
BUG: KCSAN: data-race in shmem_file_splice_read / shmem_file_splice_read

write to 0xffff888100ab7820 of 8 bytes by task 3657 on cpu 0:
 shmem_file_splice_read+0x401/0x590 mm/shmem.c:3592
 do_splice_read fs/splice.c:980 [inline]
 splice_direct_to_actor+0x261/0x680 fs/splice.c:1084
 do_splice_direct_actor fs/splice.c:1202 [inline]
 do_splice_direct+0x119/0x1a0 fs/splice.c:1228
 do_sendfile+0x37d/0x640 fs/read_write.c:1371
 __do_sys_sendfile64 fs/read_write.c:1432 [inline]
 __se_sys_sendfile64 fs/read_write.c:1418 [inline]
 __x64_sys_sendfile64+0x105/0x150 fs/read_write.c:1418
 x64_sys_call+0x1015/0x2550 arch/x86/include/generated/asm/syscalls_64.h:41
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x112/0x360 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

write to 0xffff888100ab7820 of 8 bytes by task 3658 on cpu 1:
 shmem_file_splice_read+0x401/0x590 mm/shmem.c:3592
 do_splice_read fs/splice.c:980 [inline]
 splice_direct_to_actor+0x261/0x680 fs/splice.c:1084
 do_splice_direct_actor fs/splice.c:1202 [inline]
 do_splice_direct+0x119/0x1a0 fs/splice.c:1228
 do_sendfile+0x37d/0x640 fs/read_write.c:1371
 __do_sys_sendfile64 fs/read_write.c:1432 [inline]
 __se_sys_sendfile64 fs/read_write.c:1418 [inline]
 __x64_sys_sendfile64+0x105/0x150 fs/read_write.c:1418
 x64_sys_call+0x1015/0x2550 arch/x86/include/generated/asm/syscalls_64.h:41
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x112/0x360 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x000000000000e000 -> 0x0000000000010000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3658 Comm: syz-executor185 Not tainted syzkaller #0 PREEMPT(lazy) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
==================================================================
==================================================================
BUG: KCSAN: data-race in do_sendfile / do_sendfile

write to 0xffff888100ab77e8 of 8 bytes by task 3657 on cpu 0:
 do_sendfile+0x44c/0x640 fs/read_write.c:1389
 __do_sys_sendfile64 fs/read_write.c:1432 [inline]
 __se_sys_sendfile64 fs/read_write.c:1418 [inline]
 __x64_sys_sendfile64+0x105/0x150 fs/read_write.c:1418
 x64_sys_call+0x1015/0x2550 arch/x86/include/generated/asm/syscalls_64.h:41
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x112/0x360 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888100ab77e8 of 8 bytes by task 3658 on cpu 1:
 do_sendfile+0x116/0x640 fs/read_write.c:1322
 __do_sys_sendfile64 fs/read_write.c:1432 [inline]
 __se_sys_sendfile64 fs/read_write.c:1418 [inline]
 __x64_sys_sendfile64+0x105/0x150 fs/read_write.c:1418
 x64_sys_call+0x1015/0x2550 arch/x86/include/generated/asm/syscalls_64.h:41
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x112/0x360 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x000000000000c000 -> 0x000000000000b000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3658 Comm: syz-executor185 Not tainted syzkaller #0 PREEMPT(lazy) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
==================================================================
==================================================================
BUG: KCSAN: data-race in do_sendfile / do_sendfile

write to 0xffff888100ab77e8 of 8 bytes by task 3657 on cpu 0:
 do_sendfile+0x44c/0x640 fs/read_write.c:1389
 __do_sys_sendfile64 fs/read_write.c:1432 [inline]
 __se_sys_sendfile64 fs/read_write.c:1418 [inline]
 __x64_sys_sendfile64+0x105/0x150 fs/read_write.c:1418
 x64_sys_call+0x1015/0x2550 arch/x86/include/generated/asm/syscalls_64.h:41
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x112/0x360 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

write to 0xffff888100ab77e8 of 8 bytes by task 3658 on cpu 1:
 do_sendfile+0x44c/0x640 fs/read_write.c:1389
 __do_sys_sendfile64 fs/read_write.c:1432 [inline]
 __se_sys_sendfile64 fs/read_write.c:1418 [inline]
 __x64_sys_sendfile64+0x105/0x150 fs/read_write.c:1418
 x64_sys_call+0x1015/0x2550 arch/x86/include/generated/asm/syscalls_64.h:41
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x112/0x360 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x000000000000a000 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3658 Comm: syz-executor185 Not tainted syzkaller #0 PREEMPT(lazy) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
==================================================================
==================================================================
BUG: KCSAN: data-race in do_sendfile / generic_file_llseek_size

write to 0xffff888100ab77e8 of 8 bytes by task 3657 on cpu 0:
 do_sendfile+0x44c/0x640 fs/read_write.c:1389
 __do_sys_sendfile64 fs/read_write.c:1432 [inline]
 __se_sys_sendfile64 fs/read_write.c:1418 [inline]
 __x64_sys_sendfile64+0x105/0x150 fs/read_write.c:1418
 x64_sys_call+0x1015/0x2550 arch/x86/include/generated/asm/syscalls_64.h:41
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x112/0x360 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

write to 0xffff888100ab77e8 of 8 bytes by task 3658 on cpu 1:
 vfs_setpos_cookie fs/read_write.c:66 [inline]
 vfs_setpos fs/read_write.c:87 [inline]
 generic_file_llseek_size+0x1bc/0x340 fs/read_write.c:187
 shmem_file_llseek+0xef/0x120 mm/shmem.c:3612
 vfs_llseek fs/read_write.c:391 [inline]
 ksys_lseek fs/read_write.c:404 [inline]
 __do_sys_lseek fs/read_write.c:414 [inline]
 __se_sys_lseek fs/read_write.c:412 [inline]
 __x64_sys_lseek+0xe8/0x160 fs/read_write.c:412
 x64_sys_call+0x156b/0x2550 arch/x86/include/generated/asm/syscalls_64.h:9
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x112/0x360 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000010000 -> 0x0000000000007000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3658 Comm: syz-executor185 Not tainted syzkaller #0 PREEMPT(lazy) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/10/11 11:37 git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git a5ebb76233b7 4f92358f .config console log report C ci2-upstream-kcsan-gce KCSAN: data-race in do_sendfile / do_sendfile
* Struck through repros no longer work on HEAD.