CVE-2024-46801

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

libfs: fix get_stashed_dentry()

get_stashed_dentry() tries to optimistically retrieve a stashed dentry from a provided location. It needs to ensure to hold rcu lock before it dereference the stashed location to prevent UAF issues. Use rcu_dereference() instead of READ_ONCE() it's effectively equivalent with some lockdep bells and whistles and it communicates clearly that this expects rcu protection.

A low impact use-after-free vulnerability was found in the Linux kernel's libfs subsystem. The get_stashed_dentry() helper in fs/libfs.c optimistically retrieves a stashed dentry but did not hold the RCU read lock while dereferencing the stashed location, so a concurrent dentry update could free the referenced memory, resulting in a use-after-free. A local attacker with the privileges needed to reach the affected path-lookup code could exploit this race to cause a kernel crash, that is, a denial of service. Red Hat assessed this flaw as Low impact with a CVSS 3.1 score of 5.5 (AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H), lower than the CVE.org score of 7.8, because exploitation requires local access and privileges and Red Hat's assessment limits the practical impact to availability.

The affected code was introduced upstream in Linux kernel version 6.9 and is not present in the Red Hat Enterprise Linux 8 and 9 kernel bases; accordingly, Red Hat Enterprise Linux 8 and 9 kernel and kernel-rt streams and Red Hat's managed Hosted OpenShift (ARO and OSD) offerings are recorded as not affected. Red Hat Enterprise Linux 6 and 7 Extended Lifecycle Support streams are out of support scope for this flaw. The Fedora community kernel is affected and is tracked as delegated, with a fix pursued through the Fedora community kernel updates.

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 do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.