CVE-2023-54311

Vulnerability

CVE-2023-54311 describes a self-deadlock in the Linux kernel's ext4 filesystem when converting inline directories in nojournal mode. The bug occurs in ext4_finish_convert_inline_dir() when it calls ext4_handle_dirty_dirblock() while already holding the directory lock, leading to a deadlock. A similar issue exists in ext4_convert_inline_data_nolock() for data files.

Exploitation

An attacker with local access can trigger the deadlock by performing a sequence of operations on an ext4 filesystem mounted with -o dirsync and formatted with -O inline_data. The provided reproducer involves creating a directory, adding files, setting an extended attribute, and then creating a file with a long name, which forces the inline directory to be converted to a block-based directory.

Impact

Successful exploitation causes a system hang due to the deadlock, resulting in a denial of service (DoS). The vulnerability does not require special privileges beyond the ability to create files and directories on the affected filesystem.

Mitigation

The fix is included in Linux kernel stable updates. Patches are available in the kernel git repository [1][2][3]. Users should apply the latest kernel updates from their distribution.