CVE-2026-23415futex: Fix UaF between futex_key_to_node_opt() and vma_replace_policy()

Official description

In the Linux kernel, the following vulnerability has been resolved: futex: Fix UaF between futex_key_to_node_opt() and vma_replace_policy() During futex_key_to_node_opt() execution, vma->vm_policy is read under speculative mmap lock and RCU. Concurrently, mbind() may call vma_replace_policy() which frees the old mempolicy immediately via kmem_cache_free(). This creates a race where __futex_key_to_node() dereferences a freed mempolicy pointer, causing a use-after-free read of mpol->mode. [ 151.412631] BUG: KASAN: slab-use-after-free in __futex_key_to_node (kernel/futex/core.c:349) [ 151.414046] Read of size 2 at addr ffff888001c49634 by task e/87 [ 151.415969] Call Trace: [ 151.416732] __asan_load2 (mm/kasan/generic.c:271) [ 151.416777] __futex_key_to_node (kernel/futex/core.c:349) [ 151.416822] get_futex_key (kernel/futex/core.c:374 kernel/futex/core.c:386 kernel/futex/core.c:593) Fix by adding rcu to __mpol_put().

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/853f70c67d1b37e368fdcb3e328c4b8c04f53ac0
• https://git.kernel.org/stable/c/7e196194ea27bd49adf3551e2aceb83498eb73fe
• https://git.kernel.org/stable/c/190a8c48ff623c3d67cb295b4536a660db2012aa