[PATCH] uml: block SIGWINCH in ptrace tester child

The process that UML uses to probe the host's ptrace capabilities can (rarely)
receive a SIGWINCH, confusing the parent.  This fixes that by blocking
SIGWINCH.
Signed-off-by: NJeff Dike <jdike@addtoit.com>
Cc: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

arch/um/os-Linux/start_up.c

@@ -49,6 +49,7 @@ static int ptrace_child(void *arg)
 	int pid = os_getpid(), ppid = getppid();
 	int sc_result;
 
+	change_sig(SIGWINCH, 0);
 	if(ptrace(PTRACE_TRACEME, 0, 0, 0) < 0){
 		perror("ptrace");
 		os_kill_process(pid, 0);