CVE-2022-0617: 
Linux Kernel vulnerability analysis and mitigation

A NULL pointer dereference vulnerability (CVE-2022-0617) was discovered in the Linux kernel's UDF file system functionality, affecting versions from Linux kernel 4.2-rc1 till 5.17-rc2. The vulnerability was found in the way user triggers udf_file_write_iter function for malicious UDF image (CVE Details, MITRE CVE).

The vulnerability occurs in the udf_expand_file_adinicb() function which calls directly ->writepage to write data expanded into a page. This implementation misses to setup inode for writeback properly, leading to a NULL pointer dereference when submitting page for IO. The issue manifests when attempting to dereference inode->i_wb during the writeback process (Kernel Commit).

A local user with the ability to mount a specially crafted UDF image could exploit this vulnerability to cause a denial of service by crashing the system (Debian Security, Ubuntu Security).

The vulnerability requires local access and the ability to mount UDF filesystems. It has been confirmed to be exploitable through a specially crafted UDF image that triggers the udf_file_write_iter function (OSS Security).

The issue was fixed in the Linux kernel through two commits: one addressing the NULL pointer dereference by marking the page dirty and using the standard writeback path (7fc3b7c2981bbd1047916ade327beccb90994eee), and another restoring i_lenAlloc when inode expansion fails (ea8569194b43f0f01f0a84c689388542c7254a1f). Various Linux distributions have released patches for their respective kernel versions (Debian Security).