[moderation] [ext4?] KCSAN: data-race in filemap_splice_read / page_cache_sync_ra

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 37816488247d Merge tag 'net-6.17-rc1' of git://git.kernel...
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1174d5bc580000
kernel config: https://syzkaller.appspot.com/x/.config?x=7136549ecfde7285
dashboard link: https://syzkaller.appspot.com/bug?extid=6d53f9493f4e7c365c3e
compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
CC: [adilger...@dilger.ca linux...@vger.kernel.org linux-...@vger.kernel.org ty...@mit.edu]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/e0a9a1ca014a/disk-37816488.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/92458dccfe6d/vmlinux-37816488.xz
kernel image: https://storage.googleapis.com/syzbot-assets/5422a32a7400/bzImage-37816488.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+6d53f9...@syzkaller.appspotmail.com

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

write to 0xffff888118807228 of 8 bytes by task 4724 on cpu 0:
filemap_splice_read+0x47e/0x6b0 mm/filemap.c:3037
ext4_file_splice_read+0x8f/0xb0 fs/ext4/file.c:158
do_splice_read fs/splice.c:979 [inline]
splice_direct_to_actor+0x26f/0x680 fs/splice.c:1083
do_splice_direct_actor fs/splice.c:1201 [inline]
do_splice_direct+0xda/0x150 fs/splice.c:1227
do_sendfile+0x380/0x650 fs/read_write.c:1370
__do_sys_sendfile64 fs/read_write.c:1431 [inline]
__se_sys_sendfile64 fs/read_write.c:1417 [inline]
__x64_sys_sendfile64+0x105/0x150 fs/read_write.c:1417
x64_sys_call+0x2bb0/0x2ff0 arch/x86/include/generated/asm/syscalls_64.h:41
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888118807228 of 8 bytes by task 4729 on cpu 1:
page_cache_sync_ra+0x326/0x6c0 mm/readahead.c:577
filemap_get_pages+0x2d0/0x1150 mm/filemap.c:2603
filemap_splice_read+0x333/0x6b0 mm/filemap.c:2991
ext4_file_splice_read+0x8f/0xb0 fs/ext4/file.c:158
do_splice_read fs/splice.c:979 [inline]
splice_direct_to_actor+0x26f/0x680 fs/splice.c:1083
do_splice_direct_actor fs/splice.c:1201 [inline]
do_splice_direct+0xda/0x150 fs/splice.c:1227
do_sendfile+0x380/0x650 fs/read_write.c:1370
__do_sys_sendfile64 fs/read_write.c:1431 [inline]
__se_sys_sendfile64 fs/read_write.c:1417 [inline]
__x64_sys_sendfile64+0x105/0x150 fs/read_write.c:1417
x64_sys_call+0x2bb0/0x2ff0 arch/x86/include/generated/asm/syscalls_64.h:41
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000007bc0 -> 0x0000000000007bf0

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 4729 Comm: syz.2.408 Not tainted 6.16.0-syzkaller-12063-g37816488247d #0 PREEMPT(voluntary)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
==================================================================


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.