linux-kernel - [PATCH 2.6.32 10/55] sparc64: fix incorrect sign extension in sys_sparc64

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Message-Id: <20160304153001.147215544@1wt.eu>
Date:	Fri, 04 Mar 2016 16:30:10 +0100
From:	Willy Tarreau <w@....eu>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	"Dmitry V. Levin" <ldv@...linux.org>,
	"David S. Miller" <davem@...emloft.net>,
	Ben Hutchings <ben@...adent.org.uk>, Willy Tarreau <w@....eu>
Subject: [PATCH 2.6.32 10/55] sparc64: fix incorrect sign extension in
 sys_sparc64_personality

2.6.32-longterm 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>
Signed-off-by: Willy Tarreau <w@....eu>
---
 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 cfa0e19..74e579b 100644
--- a/arch/sparc/kernel/sys_sparc_64.c
+++ b/arch/sparc/kernel/sys_sparc_64.c
@@ -524,7 +524,7 @@ SYSCALL_DEFINE1(sparc64_newuname, struct new_utsname __user *, name)

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

 	if (current->personality == PER_LINUX32 &&
 	    personality == PER_LINUX)
-- 
1.7.12.2.21.g234cd45.dirty