CVE-2024-42304

/// Technical description

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

ext4: make sure the first directory block is not a hole

The syzbot constructs a directory that has no dirblock but is non-inline,

i.e. the first directory block is a hole. And no errors are reported when

creating files in this directory in the following flow.

ext4_mknod

...

ext4_add_entry

// Read block 0

ext4_read_dirblock(dir, block, DIRENT)

bh = ext4_bread(NULL, inode, block, 0)

if (!bh && (type == INDEX || type == DIRENT_HTREE))

// The first directory block is a hole

// But type == DIRENT, so no error is reported.

After that, we get a directory block without '.' and '..' but with a valid

dentry. This may cause some code that relies on dot or dotdot (such as

make_indexed_dir()) to crash.

Therefore when ext4_read_dirblock() finds that the first directory block

is a hole report that the filesystem is corrupted and return an error to

avoid loadi

/// 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