From: Ard Biesheuvel ardb@kernel.org
[ Upstream commit 75fbef0a8b6b4bb19b9a91b5214f846c2dc5139e ]
The following 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@kernel.org Signed-off-by: Ingo Molnar mingo@kernel.org Link: https://lore.kernel.org/r/20200113172245.27925-5-ardb@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- arch/x86/mm/pageattr.c | 8 +------- 1 file changed, 1 insertion(+), 7 deletions(-)
diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c index 0d09cc5aad614..a19a71b4d1850 100644 --- a/arch/x86/mm/pageattr.c +++ b/arch/x86/mm/pageattr.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);