CVE-2021-47342

In the Linux kernel, the following vulnerability has been resolved: ext4:
fix possible UAF when remounting r/o a mmp-protected file system After
commit 618f003199c6 (“ext4: fix memory leak in ext4_fill_super”), after the
file system is remounted read-only, there is a race where the kmmpd thread
can exit, causing sbi->s_mmp_tsk to point at freed memory, which the call
to ext4_stop_mmpd() can trip over. Fix this by only allowing kmmpd() to
exit when it is stopped via ext4_stop_mmpd(). Bug-Report-Link:
<[email protected]>