[moderation] [ext4?] KCSAN: data-race in filemap_splice_read / ondemand_readahead (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 4cece7649650 Linux 6.9-rc1
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15e13d85180000
kernel config: https://syzkaller.appspot.com/x/.config?x=aa27611f143168c9
dashboard link: https://syzkaller.appspot.com/bug?extid=656b98a27b7fe7a54945
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
CC: [adilger...@dilger.ca linux...@vger.kernel.org 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/91f8fed376a8/disk-4cece764.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/5d5cce018aa6/vmlinux-4cece764.xz
kernel image: https://storage.googleapis.com/syzbot-assets/68d3e17c36f9/bzImage-4cece764.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+656b98...@syzkaller.appspotmail.com

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

write to 0xffff888117225b90 of 8 bytes by task 21054 on cpu 0:
filemap_splice_read+0x6cc/0x920 mm/filemap.c:2916
ext4_file_splice_read+0x95/0xc0 fs/ext4/file.c:158
do_splice_read fs/splice.c:985 [inline]
splice_direct_to_actor+0x26c/0x670 fs/splice.c:1089
do_splice_direct_actor fs/splice.c:1207 [inline]
do_splice_direct+0xd7/0x150 fs/splice.c:1233
do_sendfile+0x3b9/0x970 fs/read_write.c:1295
__do_sys_sendfile64 fs/read_write.c:1362 [inline]
__se_sys_sendfile64 fs/read_write.c:1348 [inline]
__x64_sys_sendfile64+0x110/0x150 fs/read_write.c:1348
do_syscall_64+0xd3/0x1d0
entry_SYSCALL_64_after_hwframe+0x6d/0x75

read to 0xffff888117225b90 of 8 bytes by task 21082 on cpu 1:
ondemand_readahead+0x5c3/0x6c0 mm/readahead.c:618
page_cache_sync_ra+0xe0/0xf0 mm/readahead.c:688
page_cache_sync_readahead include/linux/pagemap.h:1300 [inline]
filemap_get_pages+0x252/0xfb0 mm/filemap.c:2505
filemap_splice_read+0x360/0x920 mm/filemap.c:2870
ext4_file_splice_read+0x95/0xc0 fs/ext4/file.c:158
do_splice_read fs/splice.c:985 [inline]
splice_direct_to_actor+0x26c/0x670 fs/splice.c:1089
do_splice_direct_actor fs/splice.c:1207 [inline]
do_splice_direct+0xd7/0x150 fs/splice.c:1233
do_sendfile+0x3b9/0x970 fs/read_write.c:1295
__do_sys_sendfile64 fs/read_write.c:1362 [inline]
__se_sys_sendfile64 fs/read_write.c:1348 [inline]
__x64_sys_sendfile64+0x110/0x150 fs/read_write.c:1348
do_syscall_64+0xd3/0x1d0
entry_SYSCALL_64_after_hwframe+0x6d/0x75

value changed: 0x000000000015b000 -> 0x0000000000160000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 21082 Comm: syz-executor.0 Not tainted 6.9.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/29/2024
==================================================================


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