linux-kernel - [PATCH v4 07/12] rlimits: do security check under task

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Message-Id: <1277329933-8139-7-git-send-email-jslaby@suse.cz>
Date:	Wed, 23 Jun 2010 23:52:08 +0200
From:	Jiri Slaby <jslaby@...e.cz>
To:	jirislaby@...il.com
Cc:	Oleg Nesterov <oleg@...hat.com>, akpm@...ux-foundation.org,
	adobriyan@...il.com, nhorman@...driver.com,
	Stephen Smalley <sds@...ho.nsa.gov>,
	James Morris <jmorris@...ei.org>,
	Eric Paris <eparis@...isplace.org>,
	linux-kernel@...r.kernel.org,
	Heiko Carstens <heiko.carstens@...ibm.com>
Subject: [PATCH v4 07/12] rlimits: do security check under task_lock

Do security_task_setrlimit under task_lock. Other tasks may change
limits under our hands while we are checking limits inside the
function. From now on, they can't.

Note that all the security work is done under a spinlock here now.
Security hooks count with that, they are called from interrupt context
(like security_task_kill) and with spinlocks already held (e.g.
capable->security_capable).

Signed-off-by: Jiri Slaby <jslaby@...e.cz>
Acked-by: James Morris <jmorris@...ei.org>
Cc: Heiko Carstens <heiko.carstens@...ibm.com>
---
 kernel/sys.c |   20 ++++++++++----------
 1 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/kernel/sys.c b/kernel/sys.c
index 9dbcbbc..c762eeb 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -1277,7 +1277,7 @@ int do_setrlimit(struct task_struct *tsk, unsigned int resource,
 		struct rlimit *new_rlim)
 {
 	struct rlimit *old_rlim;
-	int retval;
+	int retval = 0;
 
 	if (resource >= RLIM_NLIMITS)
 		return -EINVAL;
@@ -1293,9 +1293,14 @@ int do_setrlimit(struct task_struct *tsk, unsigned int resource,
 		goto out;
 	}
 
-	retval = security_task_setrlimit(tsk->group_leader, resource, new_rlim);
-	if (retval)
-		goto out;
+	old_rlim = tsk->signal->rlim + resource;
+	task_lock(tsk->group_leader);
+	if (new_rlim->rlim_max > old_rlim->rlim_max &&
+			!capable(CAP_SYS_RESOURCE))
+		retval = -EPERM;
+	if (!retval)
+		retval = security_task_setrlimit(tsk->group_leader, resource,
+				new_rlim);
 
 	if (resource == RLIMIT_CPU && new_rlim->rlim_cur == 0) {
 		/*
@@ -1307,12 +1312,7 @@ int do_setrlimit(struct task_struct *tsk, unsigned int resource,
 		new_rlim->rlim_cur = 1;
 	}
 
-	old_rlim = tsk->signal->rlim + resource;
-	task_lock(tsk->group_leader);
-	if (new_rlim->rlim_max > old_rlim->rlim_max &&
-			!capable(CAP_SYS_RESOURCE))
-		retval = -EPERM;
-	else
+	if (!retval)
 		*old_rlim = *new_rlim;
 	task_unlock(tsk->group_leader);
 
-- 
1.7.1


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