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-rw-r--r--kernel/signal.c33
1 files changed, 32 insertions, 1 deletions
diff --git a/kernel/signal.c b/kernel/signal.c
index e46971560fcb..5d30ff561847 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1578,6 +1578,17 @@ static inline int may_ptrace_stop(void)
}
/*
+ * Return nonzero if there is a SIGKILL that should be waking us up.
+ * Called with the siglock held.
+ */
+static int sigkill_pending(struct task_struct *tsk)
+{
+ return ((sigismember(&tsk->pending.signal, SIGKILL) ||
+ sigismember(&tsk->signal->shared_pending.signal, SIGKILL)) &&
+ !unlikely(sigismember(&tsk->blocked, SIGKILL)));
+}
+
+/*
* This must be called with current->sighand->siglock held.
*
* This should be the path for all ptrace stops.
@@ -1590,6 +1601,26 @@ static inline int may_ptrace_stop(void)
*/
static void ptrace_stop(int exit_code, int nostop_code, siginfo_t *info)
{
+ int killed = 0;
+
+ if (arch_ptrace_stop_needed(exit_code, info)) {
+ /*
+ * The arch code has something special to do before a
+ * ptrace stop. This is allowed to block, e.g. for faults
+ * on user stack pages. We can't keep the siglock while
+ * calling arch_ptrace_stop, so we must release it now.
+ * To preserve proper semantics, we must do this before
+ * any signal bookkeeping like checking group_stop_count.
+ * Meanwhile, a SIGKILL could come in before we retake the
+ * siglock. That must prevent us from sleeping in TASK_TRACED.
+ * So after regaining the lock, we must check for SIGKILL.
+ */
+ spin_unlock_irq(&current->sighand->siglock);
+ arch_ptrace_stop(exit_code, info);
+ spin_lock_irq(&current->sighand->siglock);
+ killed = sigkill_pending(current);
+ }
+
/*
* If there is a group stop in progress,
* we must participate in the bookkeeping.
@@ -1605,7 +1636,7 @@ static void ptrace_stop(int exit_code, int nostop_code, siginfo_t *info)
spin_unlock_irq(&current->sighand->siglock);
try_to_freeze();
read_lock(&tasklist_lock);
- if (may_ptrace_stop()) {
+ if (!unlikely(killed) && may_ptrace_stop()) {
do_notify_parent_cldstop(current, CLD_TRAPPED);
read_unlock(&tasklist_lock);
schedule();