1 files changed, 3 insertions, 4 deletions

diff --git a/arch/um/os-Linux/helper.c b/arch/um/os-Linux/helper.c
index 8a78bf03b468..d13299cfa318 100644
--- a/arch/um/os-Linux/helper.c
+++ b/arch/um/os-Linux/helper.c
@@ -50,7 +50,8 @@ static int helper_child(void *arg)
 }
 
 /* Returns either the pid of the child process we run or -E* on failure.
- * XXX The alloc_stack here breaks if this is called in the tracing thread */
+ * XXX The alloc_stack here breaks if this is called in the tracing thread, so
+ * we need to receive a preallocated stack (a local buffer is ok). */
 int run_helper(void (*pre_exec)(void *), void *pre_data, char **argv,
                unsigned long *stack_out)
 {
@@ -113,10 +114,8 @@ out_close:
                 close(fds[1]);
         close(fds[0]);
 out_free:
-        if (stack_out == NULL)
+        if ((stack_out == NULL) || (*stack_out == 0))
                 free_stack(stack, 0);
-        else
-                *stack_out = stack;
         return ret;
 }