[PATCH 4.18 030/145] powerpc/pkeys: Deny read/write/execute by default

[Greg Kroah-Hartman]

4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Ram Pai <linuxram@xxxxxxxxxx>

commit de113256f8c1c24d8c79ae388bf2a5abd70f7577 upstream.

Deny all permissions on all keys, with some exceptions. pkey-0 must
allow all permissions, or else everything comes to a screaching halt.
Execute-only key must allow execute permission.

Fixes: cf43d3b26452 ("powerpc: Enable pkey subsystem")
Cc: stable@xxxxxxxxxxxxxxx # v4.16+
Signed-off-by: Ram Pai <linuxram@xxxxxxxxxx>
Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 arch/powerpc/mm/pkeys.c |    8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

--- a/arch/powerpc/mm/pkeys.c
+++ b/arch/powerpc/mm/pkeys.c
@@ -124,12 +124,10 @@ int pkey_initialize(void)
 
 	/* register mask is in BE format */
 	pkey_amr_mask = ~0x0ul;
-	pkey_iamr_mask = ~0x0ul;
+	pkey_amr_mask &= ~(0x3ul << pkeyshift(0));
 
-	for (i = 0; i < (pkeys_total - os_reserved); i++) {
-		pkey_amr_mask &= ~(0x3ul << pkeyshift(i));
-		pkey_iamr_mask &= ~(0x1ul << pkeyshift(i));
-	}
+	pkey_iamr_mask = ~0x0ul;
+	pkey_iamr_mask &= ~(0x3ul << pkeyshift(0));
 
 	pkey_uamor_mask = ~0x0ul;
 	pkey_uamor_mask &= ~(0x3ul << pkeyshift(0));