1 files changed, 59 insertions, 13 deletions

diff --git a/kernel/signal.c b/kernel/signal.c
index dbd7fe073c55..bded65187780 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -637,12 +637,12 @@ static inline bool si_fromuser(const struct siginfo *info)
 
 /*
  * Bad permissions for sending the signal
- * - the caller must hold at least the RCU read lock
+ * - the caller must hold the RCU read lock
  */
 static int check_kill_permission(int sig, struct siginfo *info,
                                  struct task_struct *t)
 {
-        const struct cred *cred = current_cred(), *tcred;
+        const struct cred *cred, *tcred;
         struct pid *sid;
         int error;
 
@@ -656,8 +656,10 @@ static int check_kill_permission(int sig, struct siginfo *info,
         if (error)
                 return error;
 
+        cred = current_cred();
         tcred = __task_cred(t);
-        if ((cred->euid ^ tcred->suid) &&
+        if (!same_thread_group(current, t) &&
+            (cred->euid ^ tcred->suid) &&
             (cred->euid ^ tcred->uid) &&
             (cred->uid  ^ tcred->suid) &&
             (cred->uid  ^ tcred->uid) &&
@@ -1083,23 +1085,24 @@ force_sig_info(int sig, struct siginfo *info, struct task_struct *t)
 /*
  * Nuke all other threads in the group.
  */
-void zap_other_threads(struct task_struct *p)
+int zap_other_threads(struct task_struct *p)
 {
-        struct task_struct *t;
+        struct task_struct *t = p;
+        int count = 0;
 
         p->signal->group_stop_count = 0;
 
-        for (t = next_thread(p); t != p; t = next_thread(t)) {
-                /*
-                 * Don't bother with already dead threads
-                 */
+        while_each_thread(p, t) {
+                count++;
+
+                /* Don't bother with already dead threads */
                 if (t->exit_state)
                         continue;
-
-                /* SIGKILL will be handled before any pending SIGSTOP */
                 sigaddset(&t->pending.signal, SIGKILL);
                 signal_wake_up(t, 1);
         }
+
+        return count;
 }
 
 struct sighand_struct *lock_task_sighand(struct task_struct *tsk, unsigned long *flags)
@@ -1124,11 +1127,14 @@ struct sighand_struct *lock_task_sighand(struct task_struct *tsk, unsigned long
 
 /*
  * send signal info to all the members of a group
- * - the caller must hold the RCU read lock at least
  */
 int group_send_sig_info(int sig, struct siginfo *info, struct task_struct *p)
 {
-        int ret = check_kill_permission(sig, info, p);
+        int ret;
+
+        rcu_read_lock();
+        ret = check_kill_permission(sig, info, p);
+        rcu_read_unlock();
 
         if (!ret && sig)
                 ret = do_send_sig_info(sig, info, p, true);
@@ -2735,3 +2741,43 @@ void __init signals_init(void)
 {
         sigqueue_cachep = KMEM_CACHE(sigqueue, SLAB_PANIC);
 }
+
+#ifdef CONFIG_KGDB_KDB
+#include <linux/kdb.h>
+/*
+ * kdb_send_sig_info - Allows kdb to send signals without exposing
+ * signal internals.  This function checks if the required locks are
+ * available before calling the main signal code, to avoid kdb
+ * deadlocks.
+ */
+void
+kdb_send_sig_info(struct task_struct *t, struct siginfo *info)
+{
+        static struct task_struct *kdb_prev_t;
+        int sig, new_t;
+        if (!spin_trylock(&t->sighand->siglock)) {
+                kdb_printf("Can't do kill command now.\n"
+                           "The sigmask lock is held somewhere else in "
+                           "kernel, try again later\n");
+                return;
+        }
+        spin_unlock(&t->sighand->siglock);
+        new_t = kdb_prev_t != t;
+        kdb_prev_t = t;
+        if (t->state != TASK_RUNNING && new_t) {
+                kdb_printf("Process is not RUNNING, sending a signal from "
+                           "kdb risks deadlock\n"
+                           "on the run queue locks. "
+                           "The signal has _not_ been sent.\n"
+                           "Reissue the kill command if you want to risk "
+                           "the deadlock.\n");
+                return;
+        }
+        sig = info->si_signo;
+        if (send_sig_info(sig, info, t))
+                kdb_printf("Fail to deliver Signal %d to process %d.\n",
+                           sig, t->pid);
+        else
+                kdb_printf("Signal %d is sent to process %d.\n", sig, t->pid);
+}
+#endif  /* CONFIG_KGDB_KDB */