[PATCH] uml: cleanup run_helper() API to fix a leak

Freeing the stack is left uselessly to the caller of run_helper in some cases
- this is taken from run_helper_thread, but here it is useless, so no caller
needs it and the only place where this happens has a potential leak - in case
of error neither run_helper() nor xterm_open() call free_stack().  At this
point passing a pointer is not needed - the stack pointer should be passed
directly, but this change is not done here.

Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Cc: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/arch/um/drivers/xterm.c b/arch/um/drivers/xterm.c
index 386f8b9..850221d 100644 (file)
--- a/arch/um/drivers/xterm.c
+++ b/arch/um/drivers/xterm.c
@@ -136,8 +136,6 @@ int xterm_open(int input, int output, int primary, void *d,
                return(pid);
        }
 
-       if(data->stack == 0) free_stack(stack, 0);
-
        if (data->direct_rcv) {
                new = os_rcv_fd(fd, &data->helper_pid);
        } else {

diff --git a/arch/um/os-Linux/helper.c b/arch/um/os-Linux/helper.c
index 8a78bf0..d13299c 100644 (file)
--- 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;
 }