[PATCH v4 04/12] rlimits: selinux, do rlimits changes under task_lock

[Jiri Slaby <jslaby@suse.cz>]

From: Oleg Nesterov <oleg@redhat.com>

When doing an exec, selinux updates rlimits in its code of current
process depending on current max. Make sure max or cur doesn't change
in the meantime by grabbing task_lock which do_prlimit needs for
changing limits too.

While at it, use rlimit helper for accessing CPU rlimit a line below.
To have a volatile access too.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: Oleg Nesterov <oleg@redhat.com>
---
 security/selinux/hooks.c |    6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index afb18a9..2a8a0a9 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -2333,13 +2333,15 @@ static void selinux_bprm_committing_creds(struct linux_binprm *bprm)
 	rc = avc_has_perm(new_tsec->osid, new_tsec->sid, SECCLASS_PROCESS,
 			  PROCESS__RLIMITINH, NULL);
 	if (rc) {
+		/* protect against do_prlimit() */
+		task_lock(current);
 		for (i = 0; i < RLIM_NLIMITS; i++) {
 			rlim = current->signal->rlim + i;
 			initrlim = init_task.signal->rlim + i;
 			rlim->rlim_cur = min(rlim->rlim_max, initrlim->rlim_cur);
 		}
-		update_rlimit_cpu(current,
-				current->signal->rlim[RLIMIT_CPU].rlim_cur);
+		task_unlock(current);
+		update_rlimit_cpu(current, rlimit(RLIMIT_CPU));
 	}
 }
 
-- 
1.7.1