KCSAN: data-race in filemap_splice_read / filemap_splice_read

Status: moderation: reported C repro on 2023/12/07 10:14
Subsystems: ext4
Labels: prio:low
[Documentation on labels]
Reported-by: syzbot+656c0f7422b03843b487@syzkaller.appspotmail.com
First crash: 1233d, last: 2d13h
▶ ▼ ✨ AI Jobs (5)
ID Workflow Result Correct Bug Created Started Finished Revision
6144d738 repro-c Reproduced: ✅ ❓ KCSAN: data-race in filemap_splice_read / filemap_splice_read 2026/09/26 23:12 2026/09/26 23:12 2026/09/26 23:45 a3c7249d
f310f88c assessment-security DenialOfService: ❌ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ✅ UserNamespace: ✅ VMGuestTrigger: ❌ VMHostTrigger: ❌ ❓ KCSAN: data-race in filemap_splice_read / filemap_splice_read 2026/05/30 23:23 2026/05/30 23:23 2026/05/31 00:08 6b4a8443
ec6b776f assessment-security 💥 KCSAN: data-race in filemap_splice_read / filemap_splice_read 2026/05/14 12:13 2026/05/14 12:13 2026/05/14 12:14 6ccb967e
470adca6 repro ❓ KCSAN: data-race in filemap_splice_read / filemap_splice_read 2026/03/06 16:47 2026/03/06 16:47 2026/03/06 17:02 31e9c887
437da85d assessment-kcsan Benign: ✅ ❓ KCSAN: data-race in filemap_splice_read / filemap_splice_read 2026/01/09 18:53 2026/01/09 18:53 2026/01/09 18:55 75199160
▶ ▼ Last patch testing requests (1)
Created Duration User Patch Repo Result
2026/09/27 01:21 12m retest repro git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git fddfc3ec31799a932bb92f1b8a84cb3d1f963be9 report job log log

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

write to 0xffff888110478220 of 8 bytes by task 3639 on cpu 1:
 filemap_splice_read+0x52a/0x790 mm/filemap.c:3149
 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:1426 [inline]
 __se_sys_sendfile64 fs/read_write.c:1418 [inline]
 __x64_sys_sendfile64+0xb8/0x150 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 0xffff888110478220 of 8 bytes by task 3638 on cpu 0:
 filemap_splice_read+0x52a/0x790 mm/filemap.c:3149
 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:1426 [inline]
 __se_sys_sendfile64 fs/read_write.c:1418 [inline]
 __x64_sys_sendfile64+0xb8/0x150 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: 0x0000000000006000 -> 0x0000000000090000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 3638 Comm: syz-executor137 Not tainted syzkaller #0 PREEMPT(lazy) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
==================================================================
==================================================================
BUG: KCSAN: data-race in filemap_splice_read / filemap_splice_read

write to 0xffff888110478220 of 8 bytes by task 3639 on cpu 1:
 filemap_splice_read+0x52a/0x790 mm/filemap.c:3149
 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:1426 [inline]
 __se_sys_sendfile64 fs/read_write.c:1418 [inline]
 __x64_sys_sendfile64+0xb8/0x150 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 0xffff888110478220 of 8 bytes by task 3638 on cpu 0:
 filemap_splice_read+0x52a/0x790 mm/filemap.c:3149
 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:1426 [inline]
 __se_sys_sendfile64 fs/read_write.c:1418 [inline]
 __x64_sys_sendfile64+0xb8/0x150 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 -> 0x0000000000090000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 3638 Comm: syz-executor137 Not tainted syzkaller #0 PREEMPT(lazy) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
==================================================================

Crashes (1678):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/09/27 01:33 git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git fddfc3ec3179 a3c7249d .config console log report C ci2-upstream-kcsan-gce KCSAN: data-race in filemap_splice_read / filemap_splice_read
2026/11/09 00:02 upstream 8a65162514fb 5cecaf1f .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in filemap_splice_read / filemap_splice_read
2026/11/07 21:02 upstream d164c7d754f0 5cecaf1f .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in filemap_splice_read / filemap_splice_read
2026/11/07 11:10 upstream d48723711bae 5cecaf1f .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in filemap_splice_read / filemap_splice_read
2026/11/06 20:15 upstream f66469d9905b 5cecaf1f .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in filemap_splice_read / filemap_splice_read
2026/11/05 23:33 upstream d68ce4e71248 5cecaf1f .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in filemap_splice_read / filemap_splice_read
2026/11/04 23:13 upstream 05441d697f7f 73438ed0 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in filemap_splice_read / filemap_splice_read
2026/10/30 21:08 upstream bd5c762ac051 0ec395f8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in filemap_splice_read / filemap_splice_read
2026/10/29 18:32 upstream c339f4010dea b498adee .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in filemap_splice_read / filemap_splice_read
2026/10/28 02:41 upstream 62c457528529 96923c60 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in filemap_splice_read / filemap_splice_read
2026/10/23 16:11 upstream a1c2b1da93f5 d566bfda .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in filemap_splice_read / filemap_splice_read
2026/10/23 01:22 upstream a1c2b1da93f5 b55fad29 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in filemap_splice_read / filemap_splice_read
2026/10/22 19:03 upstream 7be4bc52fd9e b55fad29 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in filemap_splice_read / filemap_splice_read
2026/10/22 04:42 upstream a804c5742bff 4ba27f85 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in filemap_splice_read / filemap_splice_read
2026/10/18 06:57 upstream 32c52ec87d62 432c0077 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in filemap_splice_read / filemap_splice_read
2026/10/18 00:26 upstream 58161ead29e5 432c0077 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in filemap_splice_read / filemap_splice_read
2026/10/16 23:24 upstream 2f2f7eeef8b0 4c840a2f .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in filemap_splice_read / filemap_splice_read
2026/10/16 09:34 upstream 9aa622dbaab8 3f2522c6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in filemap_splice_read / filemap_splice_read
2026/10/15 04:46 upstream 0fcb05b72344 8fb0ae89 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in filemap_splice_read / filemap_splice_read
2026/10/13 17:50 upstream 24a19b953e2a 5a1eeac4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in filemap_splice_read / filemap_splice_read
2026/10/12 17:08 upstream 24a19b953e2a 745a967f .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in filemap_splice_read / filemap_splice_read
2026/10/10 09:05 upstream fc1c25014ff8 4f92358f .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in filemap_splice_read / filemap_splice_read
2026/10/08 10:30 upstream 7b63ef2d55f2 4f6a9fcf .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in filemap_splice_read / filemap_splice_read
2026/10/07 10:23 upstream 602042bf29f6 6520ecdb .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in filemap_splice_read / filemap_splice_read
2026/10/05 07:51 upstream a90ee4305c4a 57bbd979 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in filemap_splice_read / filemap_splice_read
2026/10/04 11:30 upstream 6addb4f38557 57bbd979 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in filemap_splice_read / filemap_splice_read
2026/10/03 05:33 upstream 5e0f8396d480 57bbd979 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in filemap_splice_read / filemap_splice_read
2026/09/30 23:11 upstream 551c722f4080 38f7f0d1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in filemap_splice_read / filemap_splice_read
2026/09/30 08:20 upstream 551c722f4080 7808aef4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in filemap_splice_read / filemap_splice_read
2026/09/29 13:42 upstream 72d3fcf802c4 7bf4ea23 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in filemap_splice_read / filemap_splice_read
2026/09/28 14:13 upstream 72d3fcf802c4 a3c7249d .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in filemap_splice_read / filemap_splice_read
2026/09/28 05:27 upstream efb44d93a620 a3c7249d .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in filemap_splice_read / filemap_splice_read
2026/09/26 06:25 upstream 6812ce4e4379 a3c7249d .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in filemap_splice_read / filemap_splice_read
2026/09/25 04:21 upstream f49a343b305c f281d9d2 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in filemap_splice_read / filemap_splice_read
2026/09/24 02:48 upstream 62f4c998b297 0281b448 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in filemap_splice_read / filemap_splice_read
2026/09/23 11:21 upstream fe2ec83746e5 abce1216 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in filemap_splice_read / filemap_splice_read
2026/09/23 03:50 upstream c4e9f74da438 5207b90e .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in filemap_splice_read / filemap_splice_read
2026/09/20 03:04 upstream 518e5b794c06 853b104b .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in filemap_splice_read / filemap_splice_read
2026/09/19 08:55 upstream 17e7b8eacf4c 853b104b .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in filemap_splice_read / filemap_splice_read
2026/09/16 02:04 upstream f6e7b42bf05b 2daa4bb5 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in filemap_splice_read / filemap_splice_read
2026/09/13 11:21 upstream 2f0c1cf72f46 70a60e12 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in filemap_splice_read / filemap_splice_read
2026/09/12 10:32 upstream 3026c6e4f223 70a60e12 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in filemap_splice_read / filemap_splice_read
2026/09/11 21:15 upstream 3026c6e4f223 b6a5eeb7 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in filemap_splice_read / filemap_splice_read
2026/09/10 02:42 upstream 50d05c7c76c9 4e8b1cc6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in filemap_splice_read / filemap_splice_read
2026/09/09 01:06 upstream 893e11787f78 243b72f1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in filemap_splice_read / filemap_splice_read
2026/09/08 06:18 upstream 28924df2a08f 680aa3e1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in filemap_splice_read / filemap_splice_read
2026/09/07 06:59 upstream 88405f0ad1d5 4f7b22a0 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in filemap_splice_read / filemap_splice_read
2026/05/28 09:45 upstream eb3f4b7426cf 4c36e7e5 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in filemap_splice_read / filemap_splice_read
2026/05/13 09:41 upstream 1d5dcaa3bd65 fec2a7ee .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in filemap_splice_read / filemap_splice_read
2026/03/05 11:08 upstream ecc64d2dc9ff a9fe5c9e .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in filemap_splice_read / filemap_splice_read
2026/01/09 06:35 upstream 623fb9912f6a d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in filemap_splice_read / filemap_splice_read
2023/12/06 14:46 upstream bee0e7762ad2 e3299f55 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in filemap_splice_read / filemap_splice_read
2023/11/28 11:10 upstream df60cee26a2e 9fe51b7c .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in filemap_splice_read / filemap_splice_read
* Struck through repros no longer work on HEAD.