SELinux: hold tasklist_lock and siglock while waking wait_chldexit

SELinux has long been calling wake_up_interruptible() on
current->parent->signal->wait_chldexit without holding any locks.  It
appears that this operation should hold the tasklist_lock to dereference
current->parent and we should hold the siglock when waking up the
signal->wait_chldexit.

Signed-off-by: Eric Paris <eparis@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>

1 files changed, 7 insertions, 0 deletions

diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 03ff7db2a2ca..5f21a514f581 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -2268,7 +2268,9 @@ static void selinux_bprm_post_apply_creds(struct linux_binprm *bprm)
         struct rlimit *rlim, *initrlim;
         struct itimerval itimer;
         struct bprm_security_struct *bsec;
+        struct sighand_struct *psig;
         int rc, i;
+        unsigned long flags;
 
         tsec = current->security;
         bsec = bprm->security;
@@ -2335,7 +2337,12 @@ static void selinux_bprm_post_apply_creds(struct linux_binprm *bprm)
 
         /* Wake up the parent if it is waiting so that it can
            recheck wait permission to the new task SID. */
+        read_lock_irq(&tasklist_lock);
+        psig = current->parent->sighand;
+        spin_lock_irqsave(&psig->siglock, flags);
         wake_up_interruptible(&current->parent->signal->wait_chldexit);
+        spin_unlock_irqrestore(&psig->siglock, flags);
+        read_unlock_irq(&tasklist_lock);
 }
 
 /* superblock security operations */