[PATCH 1/4] ARM: mm: use pteval_t to represent page protection values

Will Deacon will.deacon at arm.com
Thu Sep 20 11:56:42 EDT 2012

When updating the page protection map after calculating the user_pgprot
value, the base protection map is temporarily stored in an unsigned long
type, causing truncation of the protection bits when LPAE is enabled.
This effectively means that calls to mprotect() will corrupt the upper
page attributes, clearing the XN bit unconditionally.

This patch uses pteval_t to store the intermediate protection values,
preserving the upper bits for 64-bit descriptors.

Signed-off-by: Will Deacon <will.deacon at arm.com>
 arch/arm/mm/mmu.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
index c2fa21d..b68b531 100644
--- a/arch/arm/mm/mmu.c
+++ b/arch/arm/mm/mmu.c
@@ -498,7 +498,7 @@ static void __init build_mem_type_table(void)
 	for (i = 0; i < 16; i++) {
-		unsigned long v = pgprot_val(protection_map[i]);
+		pteval_t v = pgprot_val(protection_map[i]);
 		protection_map[i] = __pgprot(v | user_pgprot);

More information about the linux-arm-kernel mailing list