[moderation] [block?] KCSAN: data-race in __kernel_write_iter / set_task_ioprio (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: ccd1cdca5cd4 Merge tag 'nfsd-6.19-1' of git://git.kernel.o..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11df489a580000
kernel config: https://syzkaller.appspot.com/x/.config?x=b319ff1b6a2797ca
dashboard link: https://syzkaller.appspot.com/bug?extid=b9b6442ccf519f794a7e
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
CC: [ax...@kernel.dk linux...@vger.kernel.org linux-...@vger.kernel.org]

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/12fc5a9ed91b/disk-ccd1cdca.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/b6208e3d3a67/vmlinux-ccd1cdca.xz
kernel image: https://storage.googleapis.com/syzbot-assets/785c07926b9a/bzImage-ccd1cdca.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b9b644...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in __kernel_write_iter / set_task_ioprio

write to 0xffff88811b6e65cc of 2 bytes by task 20200 on cpu 0:
set_task_ioprio+0x117/0x270 block/blk-ioc.c:282
__do_sys_ioprio_set block/ioprio.c:121 [inline]
__se_sys_ioprio_set+0x250/0x5a0 block/ioprio.c:65
__x64_sys_ioprio_set+0x43/0x50 block/ioprio.c:65
x64_sys_call+0x2781/0x3000 arch/x86/include/generated/asm/syscalls_64.h:252
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xca/0x2b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88811b6e65cc of 2 bytes by task 20181 on cpu 1:
__get_task_ioprio include/linux/ioprio.h:69 [inline]
get_current_ioprio include/linux/ioprio.h:84 [inline]
init_sync_kiocb include/linux/fs.h:2177 [inline]
__kernel_write_iter+0xf7/0x540 fs/read_write.c:617
dump_emit_page fs/coredump.c:1298 [inline]
dump_user_range+0x61e/0x8f0 fs/coredump.c:1372
elf_core_dump+0x1de7/0x1f80 fs/binfmt_elf.c:2111
coredump_write+0xacf/0xdf0 fs/coredump.c:1049
do_coredump fs/coredump.c:1126 [inline]
vfs_coredump+0x24f7/0x2e60 fs/coredump.c:1200
get_signal+0xd84/0xf70 kernel/signal.c:3019
arch_do_signal_or_restart+0x96/0x450 arch/x86/kernel/signal.c:337
__exit_to_user_mode_loop kernel/entry/common.c:41 [inline]
exit_to_user_mode_loop kernel/entry/common.c:75 [inline]
__exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline]
irqentry_exit_to_user_mode_prepare include/linux/irq-entry-common.h:270 [inline]
irqentry_exit_to_user_mode include/linux/irq-entry-common.h:339 [inline]
irqentry_exit+0xfb/0x560 kernel/entry/common.c:196
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618

value changed: 0x4007 -> 0x0000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 20181 Comm: syz.7.2823 Tainted: G W syzkaller #0 PREEMPT(voluntary)
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
==================================================================


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