linux-kernel - [PATCH 3.12 091/116] sparc64: fix incorrect sign extension in sys_sparc64

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Message-Id: <a6827009cb013e8cffb430e960f656d6c6b9d60e.1457082108.git.jslaby@suse.cz>
Date:	Fri,  4 Mar 2016 10:02:16 +0100
From:	Jiri Slaby <jslaby@...e.cz>
To:	stable@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, "Dmitry V. Levin" <ldv@...linux.org>,
	"David S . Miller" <davem@...emloft.net>,
	Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 091/116] sparc64: fix incorrect sign extension in sys_sparc64_personality

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

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

===============

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: Jiri Slaby <jslaby@...e.cz>
---
 arch/sparc/kernel/sys_sparc_64.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/sparc/kernel/sys_sparc_64.c b/arch/sparc/kernel/sys_sparc_64.c
index d188c591f2d6..608f9390396e 100644
--- a/arch/sparc/kernel/sys_sparc_64.c
+++ b/arch/sparc/kernel/sys_sparc_64.c
@@ -411,7 +411,7 @@ out:

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

 	if (personality(current->personality) == PER_LINUX32 &&
 	    personality(personality) == PER_LINUX)
-- 
2.7.2