Commit 15f003d20782 ("x86/mm/pat: Don't implicitly allow _PAGE_RW in
kernel_map_pages_in_pgd()") modified kernel_map_pages_in_pgd() to
manage writable permissions of memory mappings in the EFI page
table in a different way, but in the process, it removed the
ability to clear NX attributes from read-only mappings, by
clobbering the clear mask if _PAGE_RW is not being requested.
Failure to remove the NX attribute from read-only mappings is
unlikely to be a security issue, but it does prevent us from
tightening the permissions in the EFI page tables going forward,
so let's fix it now.
Fixes: 15f003d20782 ("x86/mm/pat: Don't implicitly allow _PAGE_RW in kernel_map_pages_in_pgd()
Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
---
arch/x86/mm/pat/set_memory.c | 8 +-------
1 file changed, 1 insertion(+), 7 deletions(-)
diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c
index 20823392f4f2..62a8ebe72a52 100644
--- a/arch/x86/mm/pat/set_memory.c
+++ b/arch/x86/mm/pat/set_memory.c
@@ -2215,7 +2215,7 @@ int __init kernel_map_pages_in_pgd(pgd_t *pgd, u64 pfn, unsigned long address,
.pgd = pgd,
.numpages = numpages,
.mask_set = __pgprot(0),
- .mask_clr = __pgprot(0),
+ .mask_clr = __pgprot(~page_flags & (_PAGE_NX|_PAGE_RW)),
.flags = 0,
};
@@ -2224,12 +2224,6 @@ int __init kernel_map_pages_in_pgd(pgd_t *pgd, u64 pfn, unsigned long address,
if (!(__supported_pte_mask & _PAGE_NX))
goto out;
- if (!(page_flags & _PAGE_NX))
- cpa.mask_clr = __pgprot(_PAGE_NX);
-
- if (!(page_flags & _PAGE_RW))
- cpa.mask_clr = __pgprot(_PAGE_RW);
-
if (!(page_flags & _PAGE_ENC))
cpa.mask_clr = pgprot_encrypted(cpa.mask_clr);
--
2.20.1
