CVE-2025-40348

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

slab: Avoid race on slab->objexts in allocslabobjexts

If two competing threads enter allocslabobjexts() and one of them fails to allocate the object extension vector, it might override the valid slab->objexts allocated by the other thread with OBJEXTSALLOCFAIL. This will cause the thread that lost this race and expects a valid pointer to dereference a NULL pointer later on.

Update slab->objexts atomically using cmpxchg() to avoid slab->objexts overrides by racing threads.

Thanks for Vlastimil and Suren's help with debugging.