From: Kees Cook <keescook@xxxxxxxxxxxx> Subject: mm/slab: expand CONFIG_SLAB_FREELIST_HARDENED to include SLAB Patch series "mm: Expand CONFIG_SLAB_FREELIST_HARDENED to include SLAB" In reviewing Vlastimil Babka's latest slub debug series, I realized[1] that several checks under CONFIG_SLAB_FREELIST_HARDENED weren't being applied to SLAB. Fix this by expanding the Kconfig coverage, and adding a simple double-free test for SLAB. This patch (of 2): Include SLAB caches when performing kmem_cache pointer verification. A defense against such corruption[1] should be applied to all the allocators. With this added, the "SLAB_FREE_CROSS" and "SLAB_FREE_PAGE" LKDTM tests now pass on SLAB: lkdtm: Performing direct entry SLAB_FREE_CROSS lkdtm: Attempting cross-cache slab free ... ------------[ cut here ]------------ cache_from_obj: Wrong slab cache. lkdtm-heap-b but object is from lkdtm-heap-a WARNING: CPU: 2 PID: 2195 at mm/slab.h:530 kmem_cache_free+0x8d/0x1d0 ... lkdtm: Performing direct entry SLAB_FREE_PAGE lkdtm: Attempting non-Slab slab free ... ------------[ cut here ]------------ virt_to_cache: Object is not a Slab page! WARNING: CPU: 1 PID: 2202 at mm/slab.h:489 kmem_cache_free+0x196/0x1d0 Additionally clean up neighboring Kconfig entries for clarity, readability, and redundant option removal. [1] https://github.com/ThomasKing2014/slides/raw/master/Building%20universal%20Android%20rooting%20with%20a%20type%20confusion%20vulnerability.pdf Link: http://lkml.kernel.org/r/20200625215548.389774-1-keescook@xxxxxxxxxxxx Link: http://lkml.kernel.org/r/20200625215548.389774-2-keescook@xxxxxxxxxxxx Fixes: 598a0717a816 ("mm/slab: validate cache membership under freelist hardening") Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> Acked-by: Vlastimil Babka <vbabka@xxxxxxx> Cc: Alexander Popov <alex.popov@xxxxxxxxx> Cc: Christoph Lameter <cl@xxxxxxxxx> Cc: David Rientjes <rientjes@xxxxxxxxxx> Cc: Jann Horn <jannh@xxxxxxxxxx> Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> Cc: Matthew Garrett <mjg59@xxxxxxxxxx> Cc: Pekka Enberg <penberg@xxxxxxxxxx> Cc: Roman Gushchin <guro@xxxxxx> Cc: Vijayanand Jitta <vjitta@xxxxxxxxxxxxxx> Cc: Vinayak Menon <vinmenon@xxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- init/Kconfig | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) --- a/init/Kconfig~mm-expand-config_slab_freelist_hardened-to-include-slab +++ a/init/Kconfig @@ -1913,9 +1913,8 @@ config SLAB_MERGE_DEFAULT command line. config SLAB_FREELIST_RANDOM - default n + bool "Randomize slab freelist" depends on SLAB || SLUB - bool "SLAB freelist randomization" help Randomizes the freelist order used on creating new pages. This security feature reduces the predictability of the kernel slab @@ -1923,12 +1922,14 @@ config SLAB_FREELIST_RANDOM config SLAB_FREELIST_HARDENED bool "Harden slab freelist metadata" - depends on SLUB + depends on SLAB || SLUB help Many kernel heap attacks try to target slab cache metadata and other infrastructure. This options makes minor performance sacrifices to harden the kernel slab allocator against common - freelist exploit methods. + freelist exploit methods. Some slab implementations have more + sanity-checking than others. This option is most effective with + CONFIG_SLUB. config SHUFFLE_PAGE_ALLOCATOR bool "Page allocator randomization" _
