futex: Fix UaF between futex_key_to_node_opt() and vma_replace_policy()

Summary

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().

Timeline

1. Apr 2, 2026, 11:40 AM UTCCVE published
2. Oct 16, 2026, 3:07 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: no · Technical impact: total

3. Oct 19, 2026, 6:35 PM UTCRecord last updated

Affected versions

• Linux Linux

  From c042c505210dc3453f378df432c10fff3d471bc5 · fixed in 853f70c67d1b37e368fdcb3e328c4b8c04f53ac0; From c042c505210dc3453f378df432c10fff3d471bc5 · fixed in 7e196194ea27bd49adf3551e2aceb83498eb73fe; From c042c505210dc3453f378df432c10fff3d471bc5 · fixed in 190a8c48ff623c3d67cb295b4536a660db2012aa

• Linux Linux

  6.16

• KernelLinux

  From 6.16.0 · fixed in 6.18.21; From 6.19.0 · fixed in 6.19.11

References 3