linux-kernel - [PATCH 3.2 49/87] sparc64: fix incorrect sign extension in sys_sparc64

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Date:	Mon, 08 Feb 2016 23:53:51 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org, "Dmitry V. Levin" <ldv@...linux.org>,
	"David S. Miller" <davem@...emloft.net>
Subject: [PATCH 3.2 49/87] sparc64: fix incorrect sign extension in
 sys_sparc64_personality

3.2.77-rc1 review patch.  If anyone has any objections, please let me know.

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

From: "Dmitry V. Levin" <ldv@...linux.org>

commit 525fd5a94e1be0776fa652df5c687697db508c91 upstream.

The value returned by sys_personality has type "long int".
It is saved to a variable of type "int", which is not a problem
yet because the type of task_struct->pesonality is "unsigned int".
The problem is the sign extension from "int" to "long int"
that happens on return from sys_sparc64_personality.

For example, a userspace call personality((unsigned) -EINVAL) will
result to any subsequent personality call, including absolutely
harmless read-only personality(0xffffffff) call, failing with
errno set to EINVAL.

Signed-off-by: Dmitry V. Levin <ldv@...linux.org>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 arch/sparc/kernel/sys_sparc_64.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/sparc/kernel/sys_sparc_64.c
+++ b/arch/sparc/kernel/sys_sparc_64.c
@@ -517,7 +517,7 @@ out:

 SYSCALL_DEFINE1(sparc64_personality, unsigned long, personality)
 {
-	int ret;
+	long ret;

 	if (personality(current->personality) == PER_LINUX32 &&
 	    personality(personality) == PER_LINUX)