[moderation] [mm?] KCSAN: data-race in shmem_file_splice_read / shmem_file_splice_read

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 5e3f5b81de80 Merge tag 'net-6.7-rc5' of git://git.kernel.o..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11ca707ae80000
kernel config: https://syzkaller.appspot.com/x/.config?x=ac34c1f29a8029df
dashboard link: https://syzkaller.appspot.com/bug?extid=706dde8a3e5ef992fcad
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
CC: [ak...@linux-foundation.org hu...@google.com linux-...@vger.kernel.org linu...@kvack.org]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/8894c209e25f/disk-5e3f5b81.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/42757ce1a7da/vmlinux-5e3f5b81.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a3314e0b4681/bzImage-5e3f5b81.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+706dde...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in shmem_file_splice_read / shmem_file_splice_read

write to 0xffff88812847c990 of 8 bytes by task 18473 on cpu 0:
shmem_file_splice_read+0x461/0x600 mm/shmem.c:3005
vfs_splice_read fs/splice.c:993 [inline]
splice_direct_to_actor+0x28c/0x690 fs/splice.c:1069
do_splice_direct+0x10d/0x190 fs/splice.c:1194
do_sendfile+0x3c4/0x980 fs/read_write.c:1254
__do_sys_sendfile64 fs/read_write.c:1322 [inline]
__se_sys_sendfile64 fs/read_write.c:1308 [inline]
__x64_sys_sendfile64+0x110/0x150 fs/read_write.c:1308
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0x44/0x110 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x63/0x6b

write to 0xffff88812847c990 of 8 bytes by task 18655 on cpu 1:
shmem_file_splice_read+0x461/0x600 mm/shmem.c:3005
vfs_splice_read fs/splice.c:993 [inline]
splice_direct_to_actor+0x28c/0x690 fs/splice.c:1069
do_splice_direct+0x10d/0x190 fs/splice.c:1194
do_sendfile+0x3c4/0x980 fs/read_write.c:1254
__do_sys_sendfile64 fs/read_write.c:1316 [inline]
__se_sys_sendfile64 fs/read_write.c:1308 [inline]
__x64_sys_sendfile64+0xbd/0x150 fs/read_write.c:1308
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0x44/0x110 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x63/0x6b

value changed: 0x0000000000705000 -> 0x0000000000710000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 18655 Comm: syz-executor.0 Not tainted 6.7.0-rc4-syzkaller-00111-g5e3f5b81de80 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/10/2023
==================================================================


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup