CVE-2024-40949

/// Technical description

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

mm: shmem: fix getting incorrect lruvec when replacing a shmem folio

When testing shmem swapin, I encountered the warning below on my machine.

The reason is that replacing an old shmem folio with a new one causes

mem_cgroup_migrate() to clear the old folio's memcg data. As a result,

the old folio cannot get the correct memcg's lruvec needed to remove

itself from the LRU list when it is being freed. This could lead to

possible serious problems, such as LRU list crashes due to holding the

wrong LRU lock, and incorrect LRU statistics.

To fix this issue, we can fallback to use the mem_cgroup_replace_folio()

to replace the old shmem folio.

[ 5241.100311] page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x5d9960

[ 5241.100317] head: order:4 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0

[ 5241.100319] flags: 0x17fffe0000040068(uptodate|lru|head|swapbacked|node=0|zone=2|lastcpupid=0x3ffff)

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References