[PATCH] signal: allocate siginfo when a traced task gets SIGSTOP

[Tycho Andersen]

Tracers can view SIGSTOP:

https://lore.kernel.org/lkml/87zhtthkuy.fsf@xxxxxxxxxxxx/T/#u

so let's allocate a siginfo for SIGSTOP when a task is traced.

Signed-off-by: Tycho Andersen <tycho@xxxxxxxx>
---
 kernel/signal.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/kernel/signal.c b/kernel/signal.c
index 9a32bc2088c9..ab4ba00119f4 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1056,11 +1056,14 @@ static int __send_signal(int sig, struct kernel_siginfo *info, struct task_struc
 		goto ret;
 
 	result = TRACE_SIGNAL_DELIVERED;
+
 	/*
-	 * Skip useless siginfo allocation for SIGKILL SIGSTOP,
-	 * and kernel threads.
+	 * Skip useless siginfo allocation for SIGKILL and kernel threads.
+	 * SIGSTOP is visible to tracers, so only skip allocation when the task
+	 * is not traced.
 	 */
-	if (sig_kernel_only(sig) || (t->flags & PF_KTHREAD))
+	if ((sig == SIGKILL) || (!task_is_traced(t) && sig == SIGSTOP) ||
+	    (t->flags & PF_KTHREAD))
 		goto out_set;
 
 	/*
-- 
2.19.1