copy_file.c |   19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

Index: libbb/copy_file.c
===================================================================
--- libbb/copy_file.c	(revision 2446)
+++ libbb/copy_file.c	(working copy)
@@ -83,6 +83,7 @@ int copy_file(const char *source, const 
 	if (S_ISDIR(source_stat.st_mode)) {
 		DIR *dp;
 		struct dirent *d;
+		char *existing_name;
 		mode_t saved_umask = 0;
 
 		if (!(flags & FILEUTILS_RECUR)) {
@@ -112,6 +113,20 @@ int copy_file(const char *source, const 
 			}
 
 			umask(saved_umask);
+
+			if (lstat(dest, &dest_stat) < 0)
+			{
+				bb_perror_msg("cannot stat '%s'", dest);
+				return -1;
+			}
+		}
+
+		if (is_in_ino_dev_hashtable(&source_stat, &existing_name))
+		{
+			/* source can't be a parent of dest. */
+			bb_error_msg("cannot copy a directory, `%s', into itself, `%s'",
+						  existing_name, dest);
+			return -1;
 		}
 
 		/* Recursively copy files in SOURCE.  */
@@ -127,6 +142,10 @@ int copy_file(const char *source, const 
 			new_source = concat_subpath_file(source, d->d_name);
 			if (new_source == NULL)
 				continue;
+
+			/* no component of dest must ever be found in source */
+			add_to_ino_dev_hashtable(&dest_stat, new_source);
+
 			new_dest = concat_path_file(dest, d->d_name);
 			if (copy_file(new_source, new_dest, flags) < 0)
 				status = -1;