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@suse.cz>
Acked-by: James Morris <jmorris@namei.org>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>

1 files changed, 10 insertions, 10 deletions

diff --git a/kernel/sys.c b/kernel/sys.c
index 9dbcbbcce153..c762eebdebf7 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);