CVE-2025-21933

Summary

CVE-2025-21933 is a kernel vulnerability affecting Linux systems that involves a NULL pointer dereference issue in the function update_mmu_cache_range(). This problem arises when the vmf parameter passed to update_mmu_cache() is NULL, leading to an issue in adjust_pte(). The vulnerability can cause a kernel NULL pointer dereference and may result in a system crash. The fix for this issue involves making decisions about holding the pte lock based on the configuration flag CONFIG_SPLIT_PTE_PTLOCKS rather than the value of 'ptl'. Additionally, when two virtual memory areas (vmas) map to the same page table entry (PTE), the pte lock should not be acquired again to avoid a deadlock. This vulnerability was discovered on the Atmel AT91SAM9 hardware platform.

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