CVE-2021-47114 ocfs2: fix data corruption by fallocate
- Exploited in the wild
- Not known
- Fix
- Available
What is CVE-2021-47114?
CVE-2021-47114 is a medium-severity vulnerability in Linux kernel, published on 15 Mar 2024.
Official description
In the Linux kernel, the following vulnerability has been resolved:
ocfs2: fix data corruption by fallocate
When fallocate punches holes out of inode size, if original isize is in the middle of last cluster, then the part from isize to the end of the cluster will be zeroed with buffer write, at that time isize is not yet updated to match the new size, if writeback is kicked in, it will invoke ocfs2_writepage()->block_write_full_page() where the pages out of inode size will be dropped. That will cause file corruption. Fix this by zero out eof blocks when extending the inode size.
Running the following command with qemu-image 4.2.1 can get a corrupted coverted image file easily.
qemu-img convert -p -t none -T none -f qcow2 $qcow_image \ -O qcow2 -o compat=1.1 $qcow_image.conv
The usage of fallocate in qemu is like this, it first punches holes out of inode size, then extend the inode size.
fallocate(11, FALLOC_FL_KEEP_SIZE|FALLOC_FL_PUNCH_HOLE, 2276196352, 65536) = 0 fallocate(11, 0, 2276196352, 65536) = 0
v1: https://www.spinics.net/lists/linux-fsdevel/msg193999.html v2: https://lore.kernel.org/linux-fsdevel/[email protected]/T/
Which versions are affected by CVE-2021-47114?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2021-47114?
Upgrade to a fixed version.
Is CVE-2021-47114 being exploited?
There is no known exploitation of CVE-2021-47114 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as DEBIAN-CVE-2021-47114, GHSA-9wr4-x5hv-2rw2, UBUNTU-CVE-2021-47114.