KCSAN: data-race in generic_file_buffered_read / simple_write_end

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: fb0155a0 Merge tag 'nfs-for-5.9-3' of git://git.linux-nfs...
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10f02587900000
kernel config: https://syzkaller.appspot.com/x/.config?x=9c2006d5acc5d93b
dashboard link: https://syzkaller.appspot.com/bug?extid=90b70e3998542fb36ca4
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+90b70e...@syzkaller.appspotmail.com

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

write to 0xffff888071f68610 of 8 bytes by task 3189 on cpu 1:
i_size_write include/linux/fs.h:876 [inline]
simple_write_end+0x1fa/0x360 fs/libfs.c:587
generic_perform_write+0x23b/0x390 mm/filemap.c:3512
__generic_file_write_iter+0x154/0x330 mm/filemap.c:3630
generic_file_write_iter+0x2f3/0x3e0 mm/filemap.c:3662
call_write_iter include/linux/fs.h:1882 [inline]
do_iter_readv_writev+0x32e/0x3d0 fs/read_write.c:713
do_iter_write+0x112/0x4b0 fs/read_write.c:1018
vfs_iter_write+0x4c/0x70 fs/read_write.c:1059
iter_file_splice_write+0x41a/0x770 fs/splice.c:750
do_splice_from fs/splice.c:846 [inline]
direct_splice_actor+0x95/0x160 fs/splice.c:1016
splice_direct_to_actor+0x365/0x660 fs/splice.c:971
do_splice_direct+0xf2/0x170 fs/splice.c:1059
do_sendfile+0x56a/0xba0 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+0x39/0x80 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff888071f68610 of 8 bytes by task 3180 on cpu 0:
i_size_read include/linux/fs.h:854 [inline]
generic_file_buffered_read+0x126d/0x1f60 mm/filemap.c:2266
generic_file_read_iter+0x7d/0x3e0 mm/filemap.c:2503
call_read_iter include/linux/fs.h:1876 [inline]
generic_file_splice_read+0x22b/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+0x56a/0xba0 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+0x39/0x80 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 3180 Comm: syz-executor.0 Not tainted 5.9.0-rc7-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.