prctl: exe link permission error changed from -EINVAL to -EPERM

This brings consistency with the rest of the prctl() syscall where
-EPERM is returned when failing a capability check.
Signed-off-by: Nicolas Viennot <Nicolas.Viennot@twosigma.com>
Signed-off-by: Adrian Reber <areber@redhat.com>
Reviewed-by: Serge Hallyn <serge@hallyn.com>
Link: https://lore.kernel.org/r/20200719100418.2112740-7-areber@redhat.comSigned-off-by: Christian Brauner <christian.brauner@ubuntu.com>

kernel/sys.c

@@ -2015,7 +2015,7 @@ static int prctl_set_mm_map(int opt, const void __user *addr, unsigned long data
 		 * This may have implications in the tomoyo subsystem.
 		 */
 		if (!checkpoint_restore_ns_capable(current_user_ns()))
-			return -EINVAL;
+			return -EPERM;
 
 		error = prctl_set_mm_exe_file(mm, prctl_map.exe_fd);
 		if (error)