KCSAN: data-race in generic_file_buffered_read / generic_write_end

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: d15be546 Merge tag 'media/v5.8-3' of git://git.kernel.org/..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10078c1b100000
kernel config: https://syzkaller.appspot.com/x/.config?x=f1297bd8e780a21f
dashboard link: https://syzkaller.appspot.com/bug?extid=f6f4cbb70f468745b776
compiler: clang version 11.0.0 (https://github.com/llvm/llvm-project.git ca2dcbd030eadbf0aa9b660efe864ff08af6e18b)
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+f6f4cb...@syzkaller.appspotmail.com

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

write to 0xffff8880bb4f0238 of 8 bytes by task 26891 on cpu 1:
i_size_write include/linux/fs.h:897 [inline]
generic_write_end+0x99/0x220 fs/buffer.c:2187
ext4_da_write_end+0x57e/0x760 fs/ext4/inode.c:3092
generic_perform_write+0x23b/0x390 mm/filemap.c:3329
ext4_buffered_write_iter+0x2cc/0x3b0 fs/ext4/file.c:270
ext4_file_write_iter+0x76f/0x1010 include/linux/fs.h:805
call_write_iter include/linux/fs.h:1908 [inline]
new_sync_write fs/read_write.c:503 [inline]
vfs_write+0x607/0x690 fs/read_write.c:578
ksys_write+0xce/0x180 fs/read_write.c:631
__do_sys_write fs/read_write.c:643 [inline]
__se_sys_write fs/read_write.c:640 [inline]
__x64_sys_write+0x3e/0x50 fs/read_write.c:640
do_syscall_64+0x51/0xb0 arch/x86/entry/common.c:384
entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8880bb4f0238 of 8 bytes by task 26901 on cpu 0:
i_size_read include/linux/fs.h:875 [inline]
generic_file_buffered_read+0xf9d/0x19e0 mm/filemap.c:2092
generic_file_read_iter+0x7d/0x3e0 mm/filemap.c:2326
ext4_file_read_iter+0x2d6/0x420 fs/ext4/file.c:74
call_read_iter include/linux/fs.h:1902 [inline]
generic_file_splice_read+0x22a/0x310 fs/splice.c:312
do_splice_to fs/splice.c:870 [inline]
splice_direct_to_actor+0x2a8/0x660 fs/splice.c:950
do_splice_direct+0xf2/0x170 fs/splice.c:1059
do_sendfile+0x562/0xb10 fs/read_write.c:1540
__do_sys_sendfile64 fs/read_write.c:1601 [inline]
__se_sys_sendfile64 fs/read_write.c:1587 [inline]
__x64_sys_sendfile64+0xf2/0x130 fs/read_write.c:1587
do_syscall_64+0x51/0xb0 arch/x86/entry/common.c:384
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 26901 Comm: syz-executor.0 Not tainted 5.8.0-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.