CVE-2024-50250

A buffer overrun exists in the Linux kernel. When pos and len are passed to dax_file_unshare, they are not aligned to an fsblock boundary, and the iteration of pos and length in the _iter function will reflect this.

A moderate-impact flaw was found in the Linux kernel's filesystem DAX (fsdax) implementation. When the file position and length passed to dax_file_unshare are not aligned to a filesystem block boundary, dax_unshare_iter() copies data using addresses that point to the start of the mapped page rather than to the requested file offset, so user data is copied to the wrong place and corrupted. Additionally, when the copy range does not end on a block boundary, only part of the destination block is populated, which exposes stale persistent-memory contents and results in an information disclosure. A local user with access to a file on a DAX-mounted persistent-memory filesystem could abuse unaligned unshare operations to corrupt data or disclose residual contents of other files. This issue affects the kernel and kernel-rt packages in Red Hat Enterprise Linux 9, where a fix is being pursued through the delegated maintenance process, and in Fedora. Red Hat Enterprise Linux 6, 7, and 8 streams and the hosted OpenShift cluster environments are not affected. Red Hat Product Security has rated this issue as MODERATE impact, lower than the upstream Important severity (NVD CVSS 3.1 score 7.1, CVE.org 7.8), because exploitation requires local access to a system configured with a DAX-enabled filesystem on persistent memory, which is not a common configuration.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Mitigation for this issue is either not available or the currently available options don't meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.