renameat: bring behaviour closer to POSIX

- Fail if old or new is longer than PATH_MAX with ENAMETOOLONG.

- Fail if old or new is 0 bytes long.

- Fail if old or new has dot or dot-dot as the last component of their
  path name.

The Linux kernel provides none of these behaviours.

1 files changed, 31 insertions, 4 deletions

diff --git a/src/unistd/renameat.c b/src/unistd/renameat.c
index c3b40a25..07386407 100644
--- a/src/unistd/renameat.c
+++ b/src/unistd/renameat.c
@@ -1,11 +1,38 @@
+#include <errno.h>
+#include <libgen.h>
+#include <limits.h>
 #include <stdio.h>
+#include <string.h>
 #include "syscall.h"
 
 int renameat(int oldfd, const char *old, int newfd, const char *new)
 {
-#ifdef SYS_renameat
+	char old_copy[PATH_MAX+1], new_copy[PATH_MAX+1];
+	char *base;
+
+	if (strlen(old) > PATH_MAX || strlen(new) > PATH_MAX) {
+		errno = ENAMETOOLONG;
+		return -1;
+	}
+
+	if (strlen(old) == 0 || strlen(new) == 0) {
+		errno = ENOENT;
+		return -1;
+	}
+
+	strcpy(old_copy, old);
+	strcpy(new_copy, new);
+
+	base = basename(old_copy);
+	strncpy(old_copy, base, sizeof(old_copy));
+	base = basename(new_copy);
+	strncpy(new_copy, base, sizeof(new_copy));
+
+	if (strcmp(old_copy, ".") == 0 || strcmp(old_copy, "..") == 0 ||
+	    strcmp(new_copy, ".") == 0 || strcmp(new_copy, "..") == 0) {
+		errno = EINVAL;
+		return -1;
+	}
+
 	return syscall(SYS_renameat, oldfd, old, newfd, new);
-#else
-	return syscall(SYS_renameat2, oldfd, old, newfd, new, 0);
-#endif
 }