linux-kernel - [PATCH 1/3] sys_personality: validate personality before set

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Date:	Thu, 27 May 2010 17:35:48 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Roland McGrath <roland@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Andi Kleen <andi@...stfloor.org>, "H. Peter Anvin" <hpa@...or.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Richard Henderson <rth@...ddle.net>, wezhang@...hat.com,
	linux-kernel@...r.kernel.org,
	Michael Kerrisk <mtk.manpages@...il.com>,
	William Cohen <wcohen@...hat.com>
Subject: [PATCH 1/3] sys_personality: validate personality before
	set_personality()

sys_personality(personality) is obviously wrong. It calls set_personality()
which always sets current->personality = personality and then does

	if (current->personality != personality)
		return -EINVAL;

If this "u_long" argument doesn't fit into "unsigned int" ->personality,
we return -EINVAL but change the caller's ->personality.

Move this check up to ensure the overflow is not possible, before calling
set_personality() which never fails.

Pointed-out-by: Wenming Zhang <wezhang@...hat.com>
Signed-off-by: Oleg Nesterov <oleg@...hat.com>
---

 kernel/exec_domain.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- 34-rc1/kernel/exec_domain.c~1_CK_OVERFLOW_EARLIER	2009-04-06 00:03:42.000000000 +0200
+++ 34-rc1/kernel/exec_domain.c	2010-05-27 15:15:12.000000000 +0200
@@ -193,9 +193,9 @@ SYSCALL_DEFINE1(personality, u_long, per
 	u_long old = current->personality;
 
 	if (personality != 0xffffffff) {
-		set_personality(personality);
-		if (current->personality != personality)
+		if ((unsigned int)personality != personality)
 			return -EINVAL;
+		set_personality(personality);
 	}
 
 	return (long)old;

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