CVE-2021-47114

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/