linux-kernel - [RESEND PATCH] sparc64: fix incorrect sign extension in sys_sparc64

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Message-ID: <20160111143019.GA29007@altlinux.org>
Date:	Mon, 11 Jan 2016 17:30:20 +0300
From:	"Dmitry V. Levin" <ldv@...linux.org>
To:	"David S. Miller" <davem@...emloft.net>
Cc:	sparclinux@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [RESEND PATCH] sparc64: fix incorrect sign extension in sys_sparc64_personality

Date: Sat Dec 26 22:35:13 2015 +0000

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>
Cc: <stable@...r.kernel.org>
---
 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 30e7ddb..c690c8e 100644
--- a/arch/sparc/kernel/sys_sparc_64.c
+++ b/arch/sparc/kernel/sys_sparc_64.c
@@ -413,15 +413,15 @@ out:

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

 	if (personality(current->personality) == PER_LINUX32 &&
 	    personality(personality) == PER_LINUX)
 		personality |= PER_LINUX32;
 	ret = sys_personality(personality);
 	if (personality(ret) == PER_LINUX32)
 		ret &= ~PER_LINUX32;

 	return ret;
 }

-- 
ldv