Linux Kernel EUVD-2026-27683

The vulnerability exists in the pstore (persistent storage) subsystem's ram_core module, specifically in the persistent_ram_vmap() function which maps persistent RAM regions into kernel virtual address space using the vmap() function. When vmap() fails and returns NULL, the function should propagate this error; however, due to arithmetic involving offset_in_page(start), a non-NULL pointer can be returned even on failure. The caller, persistent_ram_buffer_map(), cannot distinguish between success and failure, leading to subsequent code accessing prz->buffer through an invalid virtual address. This violates CWE-476 (Null Pointer Dereference) principles by failing to check for NULL return values from system functions before dereferencing them.