KCSAN: data-race in shmem_file_splice_read / shmem_file_splice_read

Status: moderation: reported on 2023/12/09 00:01
Subsystems: mm
Labels: race:benign prio:low
[Documentation on labels]
Reported-by: syzbot+706dde8a3e5ef992fcad@syzkaller.appspotmail.com
First crash: 1170d, last: 8h01m
▶ ▼ ✨ AI Jobs (3)
ID Workflow Result Correct Bug Created Started Finished Revision
b0384c36 assessment-security DenialOfService: ❌ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ✅ UserNamespace: ✅ VMGuestTrigger: ❌ VMHostTrigger: ❌ ❓ KCSAN: data-race in shmem_file_splice_read / shmem_file_splice_read 2026/05/21 02:41 2026/05/21 02:41 2026/05/21 03:22 cf874a1c
6bd39b22 repro 💥 KCSAN: data-race in shmem_file_splice_read / shmem_file_splice_read 2026/03/10 12:22 2026/03/10 12:22 2026/03/10 12:22 5c03941b
71db9653 assessment-kcsan Benign: ✅ Confident: ✅ ✅ KCSAN: data-race in shmem_file_splice_read / shmem_file_splice_read 2026/01/14 13:13 2026/01/14 13:13 2026/01/14 13:16 a9d6a792

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

write to 0xffff88810d6eb760 of 8 bytes by task 7033 on cpu 1:
 shmem_file_splice_read+0x401/0x590 mm/shmem.c:3589
 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 0xffff88810d6eb760 of 8 bytes by task 7038 on cpu 0:
 shmem_file_splice_read+0x401/0x590 mm/shmem.c:3589
 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: 0x000000000000235d -> 0x0000000000002365

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 7038 Comm: syz.6.1106 Not tainted syzkaller #0 PREEMPT(lazy) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
==================================================================

Crashes (3163):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/09/22 20:35 upstream c4e9f74da438 5207b90e .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in shmem_file_splice_read / shmem_file_splice_read
2026/09/22 19:00 upstream c4e9f74da438 e12281bd .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in shmem_file_splice_read / shmem_file_splice_read
2026/09/22 06:00 upstream f0100363d8c3 e12281bd .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in shmem_file_splice_read / shmem_file_splice_read
2026/09/22 05:48 upstream f0100363d8c3 e12281bd .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in shmem_file_splice_read / shmem_file_splice_read
2026/09/21 21:56 upstream f0100363d8c3 853b104b .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in shmem_file_splice_read / shmem_file_splice_read
2026/09/21 06:42 upstream 93f51579e7df 853b104b .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in shmem_file_splice_read / shmem_file_splice_read
2026/09/20 01:43 upstream 518e5b794c06 853b104b .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in shmem_file_splice_read / shmem_file_splice_read
2026/09/19 12:27 upstream 40288c9206c1 853b104b .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in shmem_file_splice_read / shmem_file_splice_read
2026/09/18 23:09 upstream 17e7b8eacf4c 853b104b .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in shmem_file_splice_read / shmem_file_splice_read
2026/09/18 09:54 upstream 5dd1818b15d9 853b104b .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in shmem_file_splice_read / shmem_file_splice_read
2026/09/17 19:47 upstream 4982d3552a3b 8d7d05f1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in shmem_file_splice_read / shmem_file_splice_read
2026/09/17 17:44 upstream 238650ef6c7c 8d7d05f1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in shmem_file_splice_read / shmem_file_splice_read
2026/09/16 23:38 upstream 238650ef6c7c 95928915 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in shmem_file_splice_read / shmem_file_splice_read
2026/09/16 21:53 upstream 238650ef6c7c 12a0a44a .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in shmem_file_splice_read / shmem_file_splice_read
2026/09/16 07:22 upstream 9b87fdc9af2f 12a0a44a .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in shmem_file_splice_read / shmem_file_splice_read
2026/09/15 18:44 upstream f6e7b42bf05b 2daa4bb5 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in shmem_file_splice_read / shmem_file_splice_read
2026/09/15 18:43 upstream f6e7b42bf05b 2daa4bb5 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in shmem_file_splice_read / shmem_file_splice_read
2026/09/15 15:04 upstream 587858367581 2daa4bb5 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in shmem_file_splice_read / shmem_file_splice_read
2026/09/15 04:41 upstream 587858367581 81a27d1a .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in shmem_file_splice_read / shmem_file_splice_read
2026/09/14 14:54 upstream 704340f1cd0d 81a27d1a .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in shmem_file_splice_read / shmem_file_splice_read
2026/09/14 09:03 upstream 704340f1cd0d 70a60e12 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in shmem_file_splice_read / shmem_file_splice_read
2026/09/13 20:11 upstream d681d7ef617e 70a60e12 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in shmem_file_splice_read / shmem_file_splice_read
2026/09/13 04:57 upstream 2f0c1cf72f46 70a60e12 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in shmem_file_splice_read / shmem_file_splice_read
2026/09/12 15:28 upstream 5225b8eec4c9 70a60e12 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in shmem_file_splice_read / shmem_file_splice_read
2026/09/12 01:47 upstream 3026c6e4f223 70a60e12 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in shmem_file_splice_read / shmem_file_splice_read
2026/09/11 21:20 upstream 3026c6e4f223 b6a5eeb7 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in shmem_file_splice_read / shmem_file_splice_read
2026/09/11 12:02 upstream 08df884136f1 b6a5eeb7 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in shmem_file_splice_read / shmem_file_splice_read
2026/09/11 00:02 upstream 08df884136f1 1fe56c0a .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in shmem_file_splice_read / shmem_file_splice_read
2026/09/10 11:25 upstream 50d05c7c76c9 1fe56c0a .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in shmem_file_splice_read / shmem_file_splice_read
2026/09/09 20:24 upstream 50d05c7c76c9 4e8b1cc6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in shmem_file_splice_read / shmem_file_splice_read
2026/09/09 18:15 upstream 893e11787f78 4e8b1cc6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in shmem_file_splice_read / shmem_file_splice_read
2026/09/09 04:53 upstream 893e11787f78 8387c273 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in shmem_file_splice_read / shmem_file_splice_read
2026/09/08 23:59 upstream 893e11787f78 243b72f1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in shmem_file_splice_read / shmem_file_splice_read
2026/09/08 16:01 upstream 28924df2a08f 243b72f1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in shmem_file_splice_read / shmem_file_splice_read
2026/09/08 01:47 upstream 28924df2a08f 680aa3e1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in shmem_file_splice_read / shmem_file_splice_read
2026/09/07 12:26 upstream df2908090cda 680aa3e1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in shmem_file_splice_read / shmem_file_splice_read
2026/09/07 10:44 upstream df2908090cda 4f7b22a0 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in shmem_file_splice_read / shmem_file_splice_read
2026/09/06 21:21 upstream 88405f0ad1d5 4f7b22a0 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in shmem_file_splice_read / shmem_file_splice_read
2026/09/06 21:19 upstream 88405f0ad1d5 4f7b22a0 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in shmem_file_splice_read / shmem_file_splice_read
2026/09/06 07:54 upstream 1fc5a74b108f 4f7b22a0 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in shmem_file_splice_read / shmem_file_splice_read
2026/09/05 18:36 upstream 0d9ff90a5422 4f7b22a0 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in shmem_file_splice_read / shmem_file_splice_read
2026/09/05 01:11 upstream bc35965f6940 4f7b22a0 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in shmem_file_splice_read / shmem_file_splice_read
2026/09/04 11:42 upstream bc35965f6940 f65209a4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in shmem_file_splice_read / shmem_file_splice_read
2026/09/03 21:23 upstream 8ab1afb2eb24 801f0966 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in shmem_file_splice_read / shmem_file_splice_read
2026/05/20 18:08 upstream df685633c3db 62fb93a2 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in shmem_file_splice_read / shmem_file_splice_read
2026/03/10 03:44 upstream 1f318b96cc84 6972f302 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in shmem_file_splice_read / shmem_file_splice_read
2026/01/14 08:34 upstream c537e12daeec d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in shmem_file_splice_read / shmem_file_splice_read
2023/12/08 12:55 upstream 5e3f5b81de80 28b24332 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in shmem_file_splice_read / shmem_file_splice_read
2023/11/23 22:26 upstream d3fa86b1a7b4 5b429f39 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in shmem_file_splice_read / shmem_file_splice_read
* Struck through repros no longer work on HEAD.