KCSAN: data-race in __mpage_writepage / generic_write_end (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 34816d20 Merge tag 'gfs2-v5.10-rc5-fixes' of git://git.ker..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15fa2d73500000
kernel config: https://syzkaller.appspot.com/x/.config?x=c949fed53798f819
dashboard link: https://syzkaller.appspot.com/bug?extid=44654951ba4e4b695fff
compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project.git 913f6005669cfb590c99865a90bc51ed0983d09d)
CC: [linux-...@vger.kernel.org linux-...@vger.kernel.org vi...@zeniv.linux.org.uk]

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

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+446549...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in __mpage_writepage / generic_write_end

write to 0xffff8881376297a8 of 8 bytes by task 15398 on cpu 1:
i_size_write include/linux/fs.h:871 [inline]
generic_write_end+0x98/0x250 fs/buffer.c:2186
fat_write_end+0x4a/0x150 fs/fat/inode.c:249
generic_perform_write+0x23e/0x3a0 mm/filemap.c:3340
__generic_file_write_iter+0x15c/0x330 mm/filemap.c:3458
generic_file_write_iter+0x75/0x130 mm/filemap.c:3490
call_write_iter include/linux/fs.h:1903 [inline]
do_iter_readv_writev+0x2cb/0x360 fs/read_write.c:740
do_iter_write+0x112/0x4b0 fs/read_write.c:866
vfs_iter_write+0x4c/0x70 fs/read_write.c:907
iter_file_splice_write+0x42a/0x780 fs/splice.c:686
do_splice_from fs/splice.c:764 [inline]
direct_splice_actor+0x80/0xa0 fs/splice.c:933
splice_direct_to_actor+0x345/0x650 fs/splice.c:888
do_splice_direct+0xf5/0x170 fs/splice.c:976
do_sendfile+0x5db/0xca0 fs/read_write.c:1257
__do_sys_sendfile64 fs/read_write.c:1318 [inline]
__se_sys_sendfile64 fs/read_write.c:1304 [inline]
__x64_sys_sendfile64+0xf2/0x130 fs/read_write.c:1304
do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8881376297a8 of 8 bytes by task 15403 on cpu 0:
i_size_read include/linux/fs.h:849 [inline]
__mpage_writepage+0x9a/0x1060 fs/mpage.c:501
write_cache_pages+0x4bc/0x7f0 mm/page-writeback.c:2246
mpage_writepages+0x6d/0x120 fs/mpage.c:714
fat_writepages+0x20/0x30 fs/fat/inode.c:205
do_writepages+0x7b/0x150 mm/page-writeback.c:2352
__filemap_fdatawrite_range+0x19d/0x1d0 mm/filemap.c:422
filemap_write_and_wait_range+0x8b/0x2a0 mm/filemap.c:655
generic_file_read_iter+0x11e/0x3d0 mm/filemap.c:2523
call_read_iter include/linux/fs.h:1897 [inline]
generic_file_splice_read+0x22a/0x310 fs/splice.c:311
do_splice_to fs/splice.c:788 [inline]
splice_direct_to_actor+0x2aa/0x650 fs/splice.c:867
do_splice_direct+0xf5/0x170 fs/splice.c:976
do_sendfile+0x5db/0xca0 fs/read_write.c:1257
__do_sys_sendfile64 fs/read_write.c:1318 [inline]
__se_sys_sendfile64 fs/read_write.c:1304 [inline]
__x64_sys_sendfile64+0xf2/0x130 fs/read_write.c:1304
do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 15403 Comm: syz-executor.3 Not tainted 5.10.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================


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[syzbot]

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