KCSAN: data-race in do_mpage_readpage / set_blocksize (5)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: ba816d3c Merge tag 'arm-soc-fixes-5.13-1' of git://git.ker..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17f390add00000
kernel config: https://syzkaller.appspot.com/x/.config?x=ff91eb7f28bdda65
dashboard link: https://syzkaller.appspot.com/bug?extid=b835723c20b8d5f40485
compiler: Debian clang version 11.0.1-2
CC: [ax...@kernel.dk linux...@vger.kernel.org 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+b83572...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in do_mpage_readpage / set_blocksize

write to 0xffff8881013ac53e of 1 bytes by task 16172 on cpu 0:
set_blocksize+0x20a/0x270 fs/block_dev.c:165
sb_set_blocksize fs/block_dev.c:175 [inline]
sb_min_blocksize+0x9d/0x120 fs/block_dev.c:191
fat_fill_super+0xe40/0x2a80 fs/fat/inode.c:1648
vfat_fill_super+0x2c/0x40 fs/fat/namei_vfat.c:1051
mount_bdev+0x1e8/0x290 fs/super.c:1368
vfat_mount+0x2d/0x40 fs/fat/namei_vfat.c:1058
legacy_get_tree+0x70/0xc0 fs/fs_context.c:592
vfs_get_tree+0x4a/0x1a0 fs/super.c:1498
do_new_mount fs/namespace.c:2905 [inline]
path_mount+0x11d4/0x1ce0 fs/namespace.c:3235
do_mount fs/namespace.c:3248 [inline]
__do_sys_mount fs/namespace.c:3456 [inline]
__se_sys_mount+0x23d/0x2e0 fs/namespace.c:3433
__x64_sys_mount+0x63/0x70 fs/namespace.c:3433
do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47
entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff8881013ac53e of 1 bytes by task 16176 on cpu 1:
do_mpage_readpage+0x6c/0x10b0 fs/mpage.c:160
mpage_readahead+0x149/0x280 fs/mpage.c:389
blkdev_readahead+0x18/0x20 fs/block_dev.c:649
read_pages+0x9f/0x530 mm/readahead.c:130
page_cache_ra_unbounded+0x3c8/0x410 mm/readahead.c:238
do_page_cache_ra mm/readahead.c:267 [inline]
force_page_cache_ra+0x246/0x280 mm/readahead.c:299
page_cache_sync_ra+0xcc/0xe0 mm/readahead.c:573
page_cache_sync_readahead include/linux/pagemap.h:879 [inline]
filemap_get_pages mm/filemap.c:2467 [inline]
filemap_read+0x388/0x1230 mm/filemap.c:2550
generic_file_read_iter+0x75/0x2c0 mm/filemap.c:2701
blkdev_read_iter+0xb9/0xf0 fs/block_dev.c:1732
call_read_iter include/linux/fs.h:2108 [inline]
new_sync_read fs/read_write.c:415 [inline]
vfs_read+0x565/0x5d0 fs/read_write.c:496
ksys_read+0xce/0x180 fs/read_write.c:634
__do_sys_read fs/read_write.c:644 [inline]
__se_sys_read fs/read_write.c:642 [inline]
__x64_sys_read+0x3e/0x50 fs/read_write.c:642
do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47
entry_SYSCALL_64_after_hwframe+0x44/0xae

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 16176 Comm: systemd-udevd Not tainted 5.13.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

[syzbot]

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