CVE-2021-47114: ocfs2: fix data corruption by fallocate
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 ocfs2writepage()->blockwritefullpage() 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 $qcowimage \ -O qcow2 -o compat=1.1 $qcowimage.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, FALLOCFLKEEPSIZE|FALLOCFLPUNCHHOLE, 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/20210525093034.GB4112@quack2.suse.cz/T/
Affected Software
Remediation
Event History
Frequently Asked Questions
What is the severity of CVE-2021-47114?
CVE-2021-47114 is classified with a moderate severity level due to the potential for data corruption.
How do I fix CVE-2021-47114?
To fix CVE-2021-47114, update the Linux kernel to the latest stable version that includes the patch for this vulnerability.
What systems are affected by CVE-2021-47114?
CVE-2021-47114 affects the Linux Kernel and QEMU's qemu-img utility.
What type of vulnerability is CVE-2021-47114?
CVE-2021-47114 is a data corruption vulnerability that occurs when using fallocate to manipulate file allocations.
Does CVE-2021-47114 require immediate action?
Yes, administrators should assess their systems and apply necessary updates to mitigate potential data corruption risks.