CVE-2021-47119

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> ext4: fix memory leak in ext4_fill_super<br /> <br /> Buffer head references must be released before calling kill_bdev();<br /> otherwise the buffer head (and its page referenced by b_data) will not<br /> be freed by kill_bdev, and subsequently that bh will be leaked.<br /> <br /> If blocksizes differ, sb_set_blocksize() will kill current buffers and<br /> page cache by using kill_bdev(). And then super block will be reread<br /> again but using correct blocksize this time. sb_set_blocksize() didn&amp;#39;t<br /> fully free superblock page and buffer head, and being busy, they were<br /> not freed and instead leaked.<br /> <br /> This can easily be reproduced by calling an infinite loop of:<br /> <br /> systemctl start .mount, and<br /> systemctl stop .mount<br /> <br /> ... since systemd creates a cgroup for each slice which it mounts, and<br /> the bh leak get amplified by a dying memory cgroup that also never<br /> gets freed, and memory consumption is much more easily noticed.