linux-kernel - [PATCH 06/11] rlimits: do security check under task

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Date:	Fri,  7 May 2010 10:55:37 +0200
From:	Jiri Slaby <jslaby@...e.cz>
To:	akpm@...ux-foundation.org
Cc:	torvalds@...ux-foundation.org, adobriyan@...il.com,
	nhorman@...driver.com, oleg@...hat.com,
	linux-kernel@...r.kernel.org, jirislaby@...il.com,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	Ingo Molnar <mingo@...e.hu>
Subject: [PATCH 06/11] 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.

Signed-off-by: Jiri Slaby <jslaby@...e.cz>
Acked-by: James Morris <jmorris@...ei.org>
Cc: Heiko Carstens <heiko.carstens@...ibm.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Ingo Molnar <mingo@...e.hu>
---
 kernel/sys.c |   16 +++++++---------
 1 files changed, 7 insertions(+), 9 deletions(-)

diff --git a/kernel/sys.c b/kernel/sys.c
index eb21661..9e9a3a7 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;
@@ -1293,10 +1293,6 @@ int do_setrlimit(struct task_struct *tsk, unsigned int resource,
 		goto out;
 	}
 
-	retval = security_task_setrlimit(tsk, resource, new_rlim);
-	if (retval)
-		goto out;
-
 	if (resource == RLIMIT_CPU && new_rlim->rlim_cur == 0) {
 		/*
 		 * The caller is asking for an immediate RLIMIT_CPU
@@ -1309,11 +1305,13 @@ int do_setrlimit(struct task_struct *tsk, unsigned int resource,
 
 	old_rlim = tsk->signal->rlim + resource;
 	task_lock(tsk->group_leader);
-	if ((new_rlim->rlim_max <= old_rlim->rlim_max) ||
-				capable(CAP_SYS_RESOURCE))
-		*old_rlim = *new_rlim;
-	else
+	if ((new_rlim->rlim_max > old_rlim->rlim_max) &&
+				!capable(CAP_SYS_RESOURCE))
 		retval = -EPERM;
+	if (!retval)
+		retval = security_task_setrlimit(tsk, resource, new_rlim);
+	if (!retval)
+		*old_rlim = *new_rlim;
 	task_unlock(tsk->group_leader);
 
 	if (retval || resource != RLIMIT_CPU)
-- 
1.7.1


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