CVE-2024-35846: 
Linux Kernel vulnerability analysis and mitigation

CVE-2024-35846 is a vulnerability discovered in the Linux kernel's zswap shrinker component. The issue was identified on May 17, 2024, affecting Linux kernel versions from 6.8 up to (excluding) 6.8.9, and various 6.9 release candidates (rc1-rc5). The vulnerability occurs when memory cgroup (memcg) is disabled with the boot time flag, causing the zswap shrinker to be called with sc->memcg == NULL, which leads to a NULL pointer dereference (NVD).

The vulnerability is a NULL pointer dereference in the zswap shrinker component. When memcg is disabled using the boot time flag cgroup_disable=memory, the zswap shrinker might get called with sc->memcg == NULL. While this is acceptable in some operations like lruvec, it causes a crash in memcg_page_state() due to the non-node accounting of cgroup's zswap memory. The issue has been assigned a CVSS v3.1 Base Score of 5.5 (MEDIUM) with vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H (NVD).

The vulnerability can lead to system crashes when the zswap shrinker is triggered under specific conditions with memory cgroup disabled. This primarily affects system stability and availability, with no direct impact on confidentiality or integrity (NVD).

The vulnerability requires local access and can be triggered when the system is configured with cgroup_disable=memory boot parameter. The issue was initially reported through bug trackers of libguestfs and Red Hat bugzilla, and has been confirmed reproducible in local testing environments (Kernel Patch).

A fix has been implemented in the Linux kernel through patches that modify the zswap shrinker's behavior to properly handle NULL memcg cases. The fix involves checking for disabled memory cgroups using mem_cgroup_disabled() before attempting to access memcg stats. Users should upgrade to patched kernel versions when available (Kernel Patch).