CVE-2022-49547

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

btrfs: fix deadlock between concurrent dio writes when low on free data space

When reserving data space for a direct IO write we can end up deadlocking

if we have multiple tasks attempting a write to the same file range, there

are multiple extents covered by that file range, we are low on available

space for data and the writes don't expand the inode's i_size.

The deadlock can happen like this:

1) We have a file with an i_size of 1M, at offset 0 it has an extent with

a size of 128K and at offset 128K it has another extent also with a

size of 128K;

2) Task A does a direct IO write against file range [0, 256K), and because

the write is within the i_size boundary, it takes the inode's lock (VFS

level) in shared mode;

3) Task A locks the file range [0, 256K) at btrfs_dio_iomap_begin(), and

then gets the extent map for the extent covering the range [0, 128K).

At btrfs_get_blocks_direct_write(), it cr

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References