CVE-2024-44973

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

mm, slub: do not call do_slab_free for kfence object

In 782f8906f805 the freeing of kfence objects was moved from deep inside do_slab_free to the wrapper functions outside. This is a nice change, but unfortunately it missed one spot in __kmem_cache_free_bulk.

This results in a crash like this:

BUG skbuff_head_cache (Tainted: G S B E ): Padding overwritten. 0xffff88907fea0f00-0xffff88907fea0fff @offset=3840

slab_err (mm/slub.c:1129) free_to_partial_list (mm/slub.c:? mm/slub.c:4036) slab_pad_check (mm/slub.c:864 mm/slub.c:1290) check_slab (mm/slub.c:?) free_to_partial_list (mm/slub.c:3171 mm/slub.c:4036) kmem_cache_alloc_bulk (mm/slub.c:? mm/slub.c:4495 mm/slub.c:4586 mm/slub.c:4635) napi_build_skb (net/core/skbuff.c:348 net/core/skbuff.c:527 net/core/skbuff.c:549)

All the other callers to do_slab_free appear to be ok.

Add a kfence_free check in __kmem_cache_free_bulk to avoid the crash.

This vulnerability is rated as Moderate severity because exploitation requires local system access and is restricted to causing a kernel crash and denial of service, with no compromise to system confidentiality or integrity. The flawed memory-freeing logic was introduced in upstream kernel versions that are newer than those provided in supported releases such as Red Hat Enterprise Linux 8 and 9, which remain unaffected. For environments running affected upstream kernels, standard unprivileged local interactions with subsystems invoking bulk object free routines could trigger this slab corruption.

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.