linux-kernel - [PATCH] Yama: handle 32-bit userspace prctl

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Message-ID: <20120827183813.GA23991@www.outflux.net>
Date:	Mon, 27 Aug 2012 11:38:13 -0700
From:	Kees Cook <keescook@...omium.org>
To:	linux-kernel@...r.kernel.org
Cc:	James Morris <james.l.morris@...cle.com>,
	Kees Cook <keescook@...omium.org>,
	John Johansen <john.johansen@...onical.com>,
	Dan Carpenter <dan.carpenter@...cle.com>,
	linux-security-module@...r.kernel.org
Subject: [PATCH] Yama: handle 32-bit userspace prctl

When running a 64-bit kernel and receiving prctls from a 32-bit
userspace, the "-1" used as an unsigned long will end up being
misdetected. The kernel is looking for 0xffffffffffffffff instead of
0xffffffff. Since prctl lacks a distinct compat interface, Yama needs
to handle this translation itself. As such, support either value as
meaning PR_SET_PTRACER_ANY, to avoid breaking the ABI for 64-bit.

Signed-off-by: Kees Cook <keescook@...omium.org>
Cc: stable@...r.kernel.org
---
 security/yama/yama_lsm.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/security/yama/yama_lsm.c b/security/yama/yama_lsm.c
index 0cc99a3..dcd6178 100644
--- a/security/yama/yama_lsm.c
+++ b/security/yama/yama_lsm.c
@@ -143,7 +143,7 @@ static int yama_task_prctl(int option, unsigned long arg2, unsigned long arg3,
 		if (arg2 == 0) {
 			yama_ptracer_del(NULL, myself);
 			rc = 0;
-		} else if (arg2 == PR_SET_PTRACER_ANY) {
+		} else if (arg2 == PR_SET_PTRACER_ANY || (int)arg2 == -1) {
 			rc = yama_ptracer_add(NULL, myself);
 		} else {
 			struct task_struct *tracer;
-- 
1.7.0.4


-- 
Kees Cook
Chrome OS Security
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