KCSAN: data-race in __kernel_write_iter / set_task_ioprio (4)

Status: moderation: reported C repro on 2026/09/14 19:24
Subsystems: block
Labels: race:benign prio:high
[Documentation on labels]
Reported-by: syzbot+feeb9b5352b9ff89618a@syzkaller.appspotmail.com
First crash: 32d, last: 2d19h
▶ ▼ ✨ AI Jobs (3)
ID Workflow Result Correct Bug Created Started Finished Revision
ec351270 repro-c Reproduced: ✅ ❓ KCSAN: data-race in __kernel_write_iter / set_task_ioprio (4) 2026/10/14 18:00 2026/10/14 18:01 2026/10/14 19:24 8fb0ae89
708f8c5c assessment-security DenialOfService: ✅ Exploitable: ✅ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ✅ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ❌ ❓ KCSAN: data-race in __kernel_write_iter / set_task_ioprio (4) 2026/09/16 00:03 2026/09/16 00:03 2026/09/16 00:44 2daa4bb5
7497ee99 assessment-kcsan Benign: ✅ ❓ KCSAN: data-race in __kernel_write_iter / set_task_ioprio (4) 2026/09/14 19:24 2026/09/14 19:24 2026/09/14 20:06 81a27d1a
▶ ▼ Similar bugs (3)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KCSAN: data-race in __kernel_write_iter / set_task_ioprio (2) block 6 1 504d 504d 0/29 auto-obsoleted due to no activity on 2025/07/26 03:33
upstream KCSAN: data-race in __kernel_write_iter / set_task_ioprio block 6 7 584d 724d 0/29 auto-obsoleted due to no activity on 2025/05/06 16:02
upstream KCSAN: data-race in __kernel_write_iter / set_task_ioprio (3) prio:low block 6 6 127d 294d 0/29 auto-obsoleted due to no activity on 2026/08/07 00:19
▶ ▼ Last patch testing requests (1)
Created Duration User Patch Repo Result
2026/10/14 19:32 12m retest repro git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 4056b3c9d3c92ea45955641dbafeb9b960e146ef report job log log

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

write to 0xffff8881046c1a90 of 8 bytes by task 3653 on cpu 1:
 set_task_ioprio+0x24e/0x270 block/blk-ioc.c:280
 __do_sys_ioprio_set block/ioprio.c:86 [inline]
 __se_sys_ioprio_set+0x34d/0x5c0 block/ioprio.c:65
 __x64_sys_ioprio_set+0x43/0x50 block/ioprio.c:65
 x64_sys_call+0x1d57/0x2550 arch/x86/include/generated/asm/syscalls_64.h:252
 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 0xffff8881046c1a90 of 8 bytes by task 4170 on cpu 0:
 __get_task_ioprio include/linux/ioprio.h:59 [inline]
 get_current_ioprio include/linux/ioprio.h:84 [inline]
 init_sync_kiocb include/linux/fs.h:2190 [inline]
 __kernel_write_iter+0xd3/0x590 fs/read_write.c:619
 dump_emit_page fs/coredump.c:1293 [inline]
 dump_user_range+0xa73/0xd00 fs/coredump.c:1367
 elf_core_dump+0x21c0/0x2340 fs/binfmt_elf.c:2106
 coredump_write+0xafb/0xdd0 fs/coredump.c:1047
 do_coredump fs/coredump.c:1126 [inline]
 vfs_coredump+0x2762/0x3270 fs/coredump.c:1195
 get_signal+0xd33/0xf10 kernel/signal.c:3097
 arch_do_signal_or_restart+0x96/0x480 arch/x86/kernel/signal.c:337
 __exit_to_user_mode_loop kernel/entry/common.c:66 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:101 [inline]
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
 irqentry_exit_to_user_mode_prepare include/linux/irq-entry-common.h:244 [inline]
 irqentry_exit_to_user_mode include/linux/irq-entry-common.h:315 [inline]
 irqentry_exit+0x14d/0x610 kernel/entry/common.c:165
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:595

value changed: 0x0000000000000000 -> 0xffff888109813730

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 4170 Comm: syz-executor213 Not tainted syzkaller #0 PREEMPT(lazy) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
==================================================================
syz-executor213 (4170) used greatest stack depth: 10728 bytes left

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/10/14 19:45 git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 4056b3c9d3c9 81a27d1a .config console log report C ci2-upstream-kcsan-gce KCSAN: data-race in __kernel_write_iter / set_task_ioprio
2026/09/14 19:24 upstream 704340f1cd0d 81a27d1a .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __kernel_write_iter / set_task_ioprio
* Struck through repros no longer work on HEAD.