KCSAN: data-race in generic_file_buffered_read / generic_file_buffered

KCSAN: data-race in generic_file_buffered_read / generic_file_buffered_read
Status: moderation: reported on 2020/06/22 14:27
Reported-by: syzbot+ab0dea0aed2dec8107a8@syzkaller.appspotmail.com
First crash: 16d, last: 1d20h

Sample crash report:

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

write to 0xffff88812add24b0 of 8 bytes by task 26163 on cpu 1:
 generic_file_buffered_read+0x1396/0x1800 mm/filemap.c:2237
 generic_file_read_iter+0x7d/0x3e0 mm/filemap.c:2307
 ext4_file_read_iter+0x2d6/0x420 fs/ext4/file.c:74
 call_read_iter include/linux/fs.h:1901 [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:1521
 __do_sys_sendfile64 fs/read_write.c:1582 [inline]
 __se_sys_sendfile64 fs/read_write.c:1568 [inline]
 __x64_sys_sendfile64+0xf2/0x130 fs/read_write.c:1568
 do_syscall_64+0x51/0xb0 arch/x86/entry/common.c:359
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88812add24b0 of 8 bytes by task 26175 on cpu 0:
 generic_file_buffered_read+0x113/0x1800 mm/filemap.c:2011
 generic_file_read_iter+0x7d/0x3e0 mm/filemap.c:2307
 ext4_file_read_iter+0x2d6/0x420 fs/ext4/file.c:74
 call_read_iter include/linux/fs.h:1901 [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:1521
 __do_sys_sendfile64 fs/read_write.c:1582 [inline]
 __se_sys_sendfile64 fs/read_write.c:1568 [inline]
 __x64_sys_sendfile64+0xf2/0x130 fs/read_write.c:1568
 do_syscall_64+0x51/0xb0 arch/x86/entry/common.c:359
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 26175 Comm: syz-executor.5 Not tainted 5.8.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================

Crashes (4):
Manager	Time	Kernel	Commit	Syzkaller	Config	Log	Report	Maintainers
ci2-upstream-kcsan-gce	2020/07/03 02:11	upstream	7cc2a8ea	f30c14bf	.config	log	report	akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org
ci2-upstream-kcsan-gce	2020/06/30 02:58	upstream	7c30b859	917afeaa	.config	log	report	akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org
ci2-upstream-kcsan-gce	2020/06/26 03:09	upstream	4a21185c	aea82c00	.config	log	report	akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org
ci2-upstream-kcsan-gce	2020/06/18 14:13	upstream	1b504402	3ea11d3f	.config	log	report	akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org