CONFIG_KMALLOC_PARTITION_TYPED: Type based slab cache selection for normal kmalloc

General informations

The Linux kernel configuration item CONFIG_KMALLOC_PARTITION_TYPED:

• prompt: Type based slab cache selection for normal kmalloc
• type: bool
• depends on: CONFIG_CC_HAS_ALLOC_TOKEN
• defined in mm/Kconfig
• found in Linux kernels: 7.2-rc+HEAD

Help text

Rely on Clang's allocation tokens to choose a slab cache, where token IDs are derived from the allocated type.

Unlike KMALLOC_PARTITION_RANDOM, cache assignment is deterministic based on type, which guarantees that objects of certain types are not placed in the same cache. This effectively mitigates certain classes of exploits that probabilistic defenses like KMALLOC_PARTITION_RANDOM only make harder but not impossible. However, this also means the cache assignment is predictable.

Clang's default token ID calculation returns a bounded hash with disjoint ranges for pointer-containing and pointerless objects: when used as the slab cache index, this prevents buffer overflows on primitive buffers from directly corrupting pointer-containing objects.

The current effectiveness of Clang's type inference can be judged by -Rpass=alloc-token, which provides diagnostics where (after dead-code elimination) type inference failed.

Requires Clang 22 or later.

Hardware

LKDDb

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Sources

This page is automaticly generated with free (libre, open) software lkddb(see lkddb-sources).

The data is retrived from:

• Linux kernel
• Linux Kernel Driver DataBase (LKDDb)

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