Skip to contentSkip to conversation

powerpc: pkey-mprotect must allow pkey-0

PATCH Superseded Ram Pai 1 participant 1 message Mar 14, 2018

Subsystems (3)
Memory management PowerPC Generic include/asm header files
lore
Share & tools
lore

Ram Pai

author
#0 lore raw

PATCH v2 1/1 powerpc: pkey-mprotect must allow pkey-0

Once an address range is associated with an allocated pkey, it cannot be reverted back to key-0. There is no valid reason for the above behavior. On the contrary applications need the ability to do so.

The patch relaxes the restriction.

Tested on powerpc.

cc Dave Hansen <[email protected]>
cc Michael Ellermen <[email protected]>
cc Ingo Molnar <[email protected]>
Signed-off-by Ram Pai <[email protected]>
---
 arch/powerpc/include/asm/pkeys.h | 19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)
arch/powerpc/include/asm/pkeys.h +14 -5
index 0409c80..3c1deec 100644
@@ -101,10 +101,18 @@ static inline u16 pte_to_pkey_bits(u64 pteflags)
 
 static inline bool mm_pkey_is_allocated(struct mm_struct *mm, int pkey)
 {
-	/* A reserved key is never considered as 'explicitly allocated' */
-	return ((pkey < arch_max_pkey()) &&
-		!__mm_pkey_is_reserved(pkey) &&
-		__mm_pkey_is_allocated(mm, pkey));
+	/* pkey 0 is allocated by default. */
+	if (!pkey)
+	       return true;
+
+	if (pkey < 0 || pkey >= arch_max_pkey())
+	       return false;
+
+	/* Reserved keys are never allocated. */
+	if (__mm_pkey_is_reserved(pkey))
+	       return false;
+
+	return __mm_pkey_is_allocated(mm, pkey);
 }
 
 extern void __arch_activate_pkey(int pkey);

@@ -150,7 +158,8 @@ static inline int mm_pkey_free(struct mm_struct *mm, int pkey)
 	if (static_branch_likely(&pkey_disabled))
 		return -1;
 
-	if (!mm_pkey_is_allocated(mm, pkey))
+	/* pkey 0 cannot be freed */
+	if (!pkey || !mm_pkey_is_allocated(mm, pkey))
 		return -EINVAL;
 
 	/*
Signature · 1 line
1.8.3.1