coredump: call do_unlinkat directly instead of sys_unlink

And stop messing with the address limit.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

fs/coredump.c

@@ -679,16 +679,11 @@ void do_coredump(const siginfo_t *siginfo)
 		 * privs and don't want to unlink another user's coredump.
 		 */
 		if (!need_suid_safe) {
-			mm_segment_t old_fs;
-
-			old_fs = get_fs();
-			set_fs(KERNEL_DS);
 			/*
 			 * If it doesn't exist, that's fine. If there's some
 			 * other problem, we'll catch it at the filp_open().
 			 */
-			(void) sys_unlink((const char __user *)cn.corename);
-			set_fs(old_fs);
+			do_unlinkat(AT_FDCWD, getname_kernel(cn.corename));
 		}
 
 		/*