Compute correct size for buffer. Avoid recomputation of lengths.

Based on Coverity reports from pull request #844.

diff --git a/tar/write.c b/tar/write.c
index 7960487f9d067700326d040b7bd45f6a84f1b8a2..fb8bb92b26e90b0aac4b515355850b330e6ad0ee 100644 (file)
--- a/tar/write.c
+++ b/tar/write.c
@@ -145,18 +145,17 @@ set_writer_options(struct bsdtar *bsdtar, struct archive *a)
 
        writer_options = getenv(ENV_WRITER_OPTIONS);
        if (writer_options != NULL) {
+               size_t module_len = sizeof(IGNORE_WRONG_MODULE_NAME) - 1;
+               size_t opt_len = strlen(writer_options) + 1;
                char *p;
                /* Set default write options. */
-               p = malloc(sizeof(IGNORE_WRONG_MODULE_NAME)
-                   + strlen(writer_options) + 1);
-               if (p == NULL)
+               if ((p = malloc(module_len + opt_len)) == NULL)
                        lafe_errc(1, errno, "Out of memory");
                /* Prepend magic code to ignore options for
                 * a format or filters which are not added to
                 * the archive write object. */
-               strncpy(p, IGNORE_WRONG_MODULE_NAME,
-                   sizeof(IGNORE_WRONG_MODULE_NAME) -1);
-               strcpy(p + sizeof(IGNORE_WRONG_MODULE_NAME) -1, writer_options);
+               memcpy(p, IGNORE_WRONG_MODULE_NAME, module_len);
+               memcpy(p, writer_options, opt_len);
                r = archive_write_set_options(a, p);
                free(p);
                if (r < ARCHIVE_WARN)
@@ -178,18 +177,18 @@ set_reader_options(struct bsdtar *bsdtar, struct archive *a)
 
        reader_options = getenv(ENV_READER_OPTIONS);
        if (reader_options != NULL) {
+               size_t module_len = sizeof(IGNORE_WRONG_MODULE_NAME) - 1;
+               size_t opt_len = strlen(reader_options) + 1;
                char *p;
                /* Set default write options. */
-               p = malloc(sizeof(IGNORE_WRONG_MODULE_NAME)
-                   + strlen(reader_options) + 1);
+               if ((p = malloc(module_len + opt_len)) == NULL)
                if (p == NULL)
                        lafe_errc(1, errno, "Out of memory");
                /* Prepend magic code to ignore options for
                 * a format or filters which are not added to
                 * the archive write object. */
-               strncpy(p, IGNORE_WRONG_MODULE_NAME,
-                   sizeof(IGNORE_WRONG_MODULE_NAME) -1);
-               strcpy(p + sizeof(IGNORE_WRONG_MODULE_NAME) -1, reader_options);
+               memcpy(p, IGNORE_WRONG_MODULE_NAME, module_len);
+               memcpy(p, reader_options, opt_len);
                r = archive_read_set_options(a, p);
                free(p);
                if (r < ARCHIVE_WARN)