cred_guard_mutex: do not return -EINTR to user-space

do_execve() and ptrace_attach() return -EINTR if
mutex_lock_interruptible(->cred_guard_mutex) fails.

This is not right, change the code to return ERESTARTNOINTR.

Perhaps we should also change proc_pid_attr_write().

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Acked-by: Roland McGrath <roland@redhat.com>
Cc: James Morris <jmorris@namei.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/compat.c

@@ -1486,8 +1486,8 @@ int compat_do_execve(char * filename,
 	if (!bprm)
 		goto out_files;
 
-	retval = mutex_lock_interruptible(&current->cred_guard_mutex);
-	if (retval < 0)
+	retval = -ERESTARTNOINTR;
+	if (mutex_lock_interruptible(&current->cred_guard_mutex))
 		goto out_free;
 	current->in_execve = 1;
 

fs/exec.c

@@ -1277,8 +1277,8 @@ int do_execve(char * filename,
 	if (!bprm)
 		goto out_files;
 
-	retval = mutex_lock_interruptible(&current->cred_guard_mutex);
-	if (retval < 0)
+	retval = -ERESTARTNOINTR;
+	if (mutex_lock_interruptible(&current->cred_guard_mutex))
 		goto out_free;
 	current->in_execve = 1;
 

kernel/ptrace.c

@@ -181,8 +181,8 @@ int ptrace_attach(struct task_struct *task)
 	 * interference; SUID, SGID and LSM creds get determined differently
 	 * under ptrace.
 	 */
-	retval = mutex_lock_interruptible(&task->cred_guard_mutex);
-	if (retval < 0)
+	retval = -ERESTARTNOINTR;
+	if (mutex_lock_interruptible(&task->cred_guard_mutex))
 		goto out;
 
 	task_lock(task);