1 files changed, 13 insertions, 2 deletions

diff --git a/lib/syscall.c b/lib/syscall.c
index e30e03932480..63239e097b13 100644
--- a/lib/syscall.c
+++ b/lib/syscall.c
@@ -7,9 +7,19 @@ static int collect_syscall(struct task_struct *target, long *callno,
                            unsigned long args[6], unsigned int maxargs,
                            unsigned long *sp, unsigned long *pc)
 {
-        struct pt_regs *regs = task_pt_regs(target);
-        if (unlikely(!regs))
+        struct pt_regs *regs;
+
+        if (!try_get_task_stack(target)) {
+                /* Task has no stack, so the task isn't in a syscall. */
+                *callno = -1;
+                return 0;
+        }
+
+        regs = task_pt_regs(target);
+        if (unlikely(!regs)) {
+                put_task_stack(target);
                 return -EAGAIN;
+        }
 
         *sp = user_stack_pointer(regs);
         *pc = instruction_pointer(regs);
@@ -18,6 +28,7 @@ static int collect_syscall(struct task_struct *target, long *callno,
         if (*callno != -1L && maxargs > 0)
                 syscall_get_arguments(target, regs, 0, maxargs, args);
 
+        put_task_stack(target);
         return 0;
 }