CVE-2024-49889

/// Technical description

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

ext4: avoid use-after-free in ext4_ext_show_leaf()

In ext4_find_extent(), path may be freed by error or be reallocated, so

using a previously saved *ppath may have been freed and thus may trigger

use-after-free, as follows:

ext4_split_extent

path = *ppath;

ext4_split_extent_at(ppath)

path = ext4_find_extent(ppath)

ext4_split_extent_at(ppath)

// ext4_find_extent fails to free path

// but zeroout succeeds

ext4_ext_show_leaf(inode, path)

eh = path[depth].p_hdr

// path use-after-free !!!

Similar to ext4_split_extent_at(), we use *ppath directly as an input to

ext4_ext_show_leaf(). Fix a spelling error by the way.

Same problem in ext4_ext_handle_unwritten_extents(). Since 'path' is only

used in ext4_ext_show_leaf(), remove 'path' and use *ppath directly.

This issue is triggered only when EXT_DEBUG is defined and therefore does

not affect functionality.

/// 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