[moderation] [fs?] KCSAN: data-race in filemap_read / filemap_splice_read (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: d9d32e5bd5a4 Merge tag 'ata-7.0-rc2' of git://git.kernel.o..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1757b55a580000
kernel config: https://syzkaller.appspot.com/x/.config?x=6b32b22d8934c136
dashboard link: https://syzkaller.appspot.com/bug?extid=6880f676b265dbd42d63
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
CC: [bra...@kernel.org ja...@suse.cz linux-...@vger.kernel.org linux-...@vger.kernel.org vi...@zeniv.linux.org.uk]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/302091701651/disk-d9d32e5b.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/2ad17634f2f7/vmlinux-d9d32e5b.xz
kernel image: https://storage.googleapis.com/syzbot-assets/63490b6937eb/bzImage-d9d32e5b.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+6880f6...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in filemap_read / filemap_splice_read

write to 0xffff88811a6f8228 of 8 bytes by task 10061 on cpu 0:
filemap_splice_read+0x523/0x780 mm/filemap.c:3125
do_splice_read fs/splice.c:980 [inline]
splice_direct_to_actor+0x26e/0x670 fs/splice.c:1084
do_splice_direct_actor fs/splice.c:1202 [inline]
do_splice_direct+0x119/0x1a0 fs/splice.c:1228
do_sendfile+0x382/0x650 fs/read_write.c:1372
__do_sys_sendfile64 fs/read_write.c:1433 [inline]
__se_sys_sendfile64 fs/read_write.c:1419 [inline]
__x64_sys_sendfile64+0x105/0x150 fs/read_write.c:1419
x64_sys_call+0x2dc4/0x3020 arch/x86/include/generated/asm/syscalls_64.h:41
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x12c/0x370 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

write to 0xffff88811a6f8228 of 8 bytes by task 10066 on cpu 1:
filemap_read+0x98d/0xa10 mm/filemap.c:2873
generic_file_read_iter+0x79/0x330 mm/filemap.c:2992
io_iter_do_read io_uring/rw.c:835 [inline]
__io_read+0x463/0xc50 io_uring/rw.c:951
io_read+0x4a/0x190 io_uring/rw.c:1031
__io_issue_sqe+0xfd/0x2d0 io_uring/io_uring.c:1384
io_issue_sqe+0x206/0xc00 io_uring/io_uring.c:1407
io_wq_submit_work+0x5bc/0x830 io_uring/io_uring.c:1519
io_worker_handle_work+0x41e/0x950 io_uring/io-wq.c:652
io_wq_worker+0x23d/0x970 io_uring/io-wq.c:706
ret_from_fork+0x150/0x360 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

value changed: 0x00000000000000d8 -> 0x00000000000014f0

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 10066 Comm: iou-wrk-10063 Tainted: G W syzkaller #0 PREEMPT(full)
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
==================================================================


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