linux-kernel - [PATCH 4.17 045/220] powerpc/pkeys: Detach execute_only key on !PROT

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Date:   Sun,  1 Jul 2018 18:21:09 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Shakeel Butt <shakeelb@...gle.com>,
        Ram Pai <linuxram@...ibm.com>,
        Thiago Jung Bauermann <bauerman@...ux.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>
Subject: [PATCH 4.17 045/220] powerpc/pkeys: Detach execute_only key on !PROT_EXEC

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

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

From: Ram Pai <linuxram@...ibm.com>

commit eabdb8ca8690eedd461e61ea7780595fbbae8132 upstream.

Disassociate the exec_key from a VMA if the VMA permission is not
PROT_EXEC anymore. Otherwise the exec_only key continues to be
associated with the vma, causing unexpected behavior.

The problem was reported on x86 by Shakeel Butt, which is also
applicable on powerpc.

Fixes: 5586cf61e108 ("powerpc: introduce execute-only pkey")
Cc: stable@...r.kernel.org # v4.16+
Reported-by: Shakeel Butt <shakeelb@...gle.com>
Signed-off-by: Ram Pai <linuxram@...ibm.com>
Reviewed-by: Thiago Jung Bauermann <bauerman@...ux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/powerpc/mm/pkeys.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/arch/powerpc/mm/pkeys.c
+++ b/arch/powerpc/mm/pkeys.c
@@ -383,9 +383,9 @@ int __arch_override_mprotect_pkey(struct
 {
 	/*
 	 * If the currently associated pkey is execute-only, but the requested
-	 * protection requires read or write, move it back to the default pkey.
+	 * protection is not execute-only, move it back to the default pkey.
 	 */
-	if (vma_is_pkey_exec_only(vma) && (prot & (PROT_READ | PROT_WRITE)))
+	if (vma_is_pkey_exec_only(vma) && (prot != PROT_EXEC))
 		return 0;
 
 	/*