CVE-2025-68293 — mm/huge_memory: fix NULL pointer deference when splitting folio

Affected: Linux

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

mm/huge_memory: fix NULL pointer deference when splitting folio

Commit c010d47f107f ("mm: thp: split huge page to any lower order pages") introduced an early check on the folio's order via mapping->flags before proceeding with the split work.

This check introduced a bug: for shmem folios in the swap cache and truncated folios, the mapping pointer can be NULL. Accessing mapping->flags in this state leads directly to a NULL pointer dereference.

This commit fixes the issue by moving the check for mapping != NULL before any attempt to access mapping->flags.

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CVE-2025-68293 — mm/huge_memory: fix NULL pointer deference when splitting folio