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x86/mm: Fix NX bit clearing issue in kernel_map_pages_in_pgd 

[ Upstream commit 75fbef0a8b ]

The following commit:

  15f003d207 ("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: 15f003d207 ("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>
5.4-rM2-2.2.x-imx-squashed
Ard Biesheuvel 2020-01-13 18:22:36 +01:00 committed by Greg Kroah-Hartman
parent 225a5b5bee
commit e7e6b53fea
1 changed files with 1 additions and 7 deletions
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8
arch/x86/mm/pageattr.c
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@ -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);