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Subject[PATCH 1/1 v2] x86: pkey-mprotect must allow pkey-0
Date
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 x86_64.

cc: Dave Hansen <dave.hansen@intel.com>
cc: Michael Ellermen <mpe@ellerman.id.au>
cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Ram Pai <linuxram@us.ibm.com>
---
arch/x86/include/asm/pkeys.h | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/pkeys.h b/arch/x86/include/asm/pkeys.h
index a0ba1ff..6ea7486 100644
--- a/arch/x86/include/asm/pkeys.h
+++ b/arch/x86/include/asm/pkeys.h
@@ -52,7 +52,7 @@ bool mm_pkey_is_allocated(struct mm_struct *mm, int pkey)
* from pkey_alloc(). pkey 0 is special, and never
* returned from pkey_alloc().
*/
- if (pkey <= 0)
+ if (pkey < 0)
return false;
if (pkey >= arch_max_pkey())
return false;
@@ -92,7 +92,8 @@ int mm_pkey_alloc(struct mm_struct *mm)
static inline
int mm_pkey_free(struct mm_struct *mm, int pkey)
{
- if (!mm_pkey_is_allocated(mm, pkey))
+ /* pkey 0 is special and can never be freed */
+ if (!pkey || !mm_pkey_is_allocated(mm, pkey))
return -EINVAL;

mm_set_pkey_free(mm, pkey);
--
1.8.3.1
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