KCSAN: data-race in blkdev_get_by_dev / blkdev_put

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 7fd2bf83d59a Merge branch 'i2c/for-current-fixed' of git:/..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12b8cb98b00000
kernel config: https://syzkaller.appspot.com/x/.config?x=25b3ed562c30cd70
dashboard link: https://syzkaller.appspot.com/bug?extid=8a14637def67055e3e8a
compiler: Debian clang version 11.0.1-2, GNU ld (GNU Binutils for Debian) 2.35.1
CC: [ax...@kernel.dk linux...@vger.kernel.org linux-...@vger.kernel.org]

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+8a1463...@syzkaller.appspotmail.com

EXT4-fs (loop2): invalid first ino: 0
==================================================================
BUG: KCSAN: data-race in blkdev_get_by_dev / blkdev_put

write to 0xffff888100405060 of 4 bytes by task 18483 on cpu 1:
blkdev_get_by_dev+0xa26/0xca0
blkdev_open+0xb3/0x130 block/fops.c:448
do_dentry_open+0x52c/0x860 fs/open.c:822
vfs_open+0x43/0x50 fs/open.c:945
do_open fs/namei.c:3428 [inline]
path_openat+0x17c3/0x1ec0 fs/namei.c:3561
do_filp_open+0x105/0x220 fs/namei.c:3588
do_sys_openat2+0xb5/0x2b0 fs/open.c:1200
do_sys_open fs/open.c:1216 [inline]
__do_sys_open fs/open.c:1224 [inline]
__se_sys_open fs/open.c:1220 [inline]
__x64_sys_open+0xe2/0x110 fs/open.c:1220
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x44/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff888100405060 of 4 bytes by task 18530 on cpu 0:
blkdev_put+0x3b/0x4c0 block/bdev.c:908
kill_block_super+0x7b/0x90 fs/super.c:1398
deactivate_locked_super+0x65/0xd0 fs/super.c:335
mount_bdev+0x204/0x290 fs/super.c:1370
ext4_mount+0x2d/0x40 fs/ext4/super.c:6515
legacy_get_tree+0x70/0xc0 fs/fs_context.c:610
vfs_get_tree+0x4a/0x1a0 fs/super.c:1498
do_new_mount fs/namespace.c:2988 [inline]
path_mount+0x11ec/0x1d20 fs/namespace.c:3318
do_mount fs/namespace.c:3331 [inline]
__do_sys_mount fs/namespace.c:3539 [inline]
__se_sys_mount+0x24b/0x2f0 fs/namespace.c:3516
__x64_sys_mount+0x63/0x70 fs/namespace.c:3516
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x44/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x00000003 -> 0x00000004

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 18530 Comm: syz-executor.2 Not tainted 5.15.0-rc4-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.