"value":"In the Linux kernel, the following vulnerability has been resolved:\n\nmm/secretmem: fix GUP-fast succeeding on secretmem folios\n\nfolio_is_secretmem() currently relies on secretmem folios being LRU\nfolios, to save some cycles.\n\nHowever, folios might reside in a folio batch without the LRU flag set, or\ntemporarily have their LRU flag cleared. Consequently, the LRU flag is\nunreliable for this purpose.\n\nIn particular, this is the case when secretmem_fault() allocates a fresh\npage and calls filemap_add_folio()->folio_add_lru(). The folio might be\nadded to the per-cpu folio batch and won't get the LRU flag set until the\nbatch was drained using e.g., lru_add_drain().\n\nConsequently, folio_is_secretmem() might not detect secretmem folios and\nGUP-fast can succeed in grabbing a secretmem folio, crashing the kernel\nwhen we would later try reading/writing to the folio, because the folio\nhas been unmapped from the directmap.\n\nFix it by removing that unreliable check."
