prot_none_hugetlb_entry() is the hugetlb callback for the early mprotect(PROT_NONE) PFN permission walk on x86. The callback passes the decoded PFN to pfn_modify_allowed(). For a hugetlb callback, the pte pointer refers to a hugetlb entry. On architectures where hugetlb entries need huge_ptep_get(), reading that entry with ptep_get() can make the permission check use the wrong PFN. Use huge_ptep_get() before decoding the hugetlb PFN. Currently there is no path which can trigger a bug: huge_ptep_get() is a simple ptep_get() for x86, and the prot_none walk occurs only for x86. But use the correct helper anyways. Fixes: 42e4089c7890 ("x86/speculation/l1tf: Disallow non privileged high MMIO PROT_NONE mappings") Signed-off-by: Dev Jain --- mm/mprotect.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/mm/mprotect.c b/mm/mprotect.c index 9cbf932b028cf..23779632d18bf 100644 --- a/mm/mprotect.c +++ b/mm/mprotect.c @@ -699,14 +699,20 @@ static int prot_none_pte_entry(pte_t *pte, unsigned long addr, 0 : -EACCES; } +#ifdef CONFIG_HUGETLB_PAGE static int prot_none_hugetlb_entry(pte_t *pte, unsigned long hmask, unsigned long addr, unsigned long next, struct mm_walk *walk) { - return pfn_modify_allowed(pte_pfn(ptep_get(pte)), + pte_t entry = huge_ptep_get(walk->mm, addr, pte); + + return pfn_modify_allowed(pte_pfn(entry), *(pgprot_t *)(walk->private)) ? 0 : -EACCES; } +#else +#define prot_none_hugetlb_entry NULL +#endif static int prot_none_test(unsigned long addr, unsigned long next, struct mm_walk *walk) -- 2.43.0