From c7746e62d09b94ddcf98b36fa3ddcfdb20c4b40b Mon Sep 17 00:00:00 2001
From: Daniel Axtens <dja@axtens.net>
Date: Tue, 20 Nov 2018 17:56:29 +1100
Subject: [PATCH] Avoid a double-free when a window size of 0 is specified

new_size can be 0 with a malicious or corrupted RAR archive.

realloc(area, 0) is equivalent to free(area), so the region would
be free()d here and the free()d again in the cleanup function.

Found with a setup running AFL, afl-rb, and qsym.
---
 libarchive/archive_read_support_format_rar.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/libarchive/archive_read_support_format_rar.c b/libarchive/archive_read_support_format_rar.c
index 23452222..6f419c27 100644
--- a/libarchive/archive_read_support_format_rar.c
+++ b/libarchive/archive_read_support_format_rar.c
@@ -2300,6 +2300,11 @@ parse_codes(struct archive_read *a)
       new_size = DICTIONARY_MAX_SIZE;
     else
       new_size = rar_fls((unsigned int)rar->unp_size) << 1;
+    if (new_size == 0) {
+      archive_set_error(&a->archive, ARCHIVE_ERRNO_FILE_FORMAT,
+                        "Zero window size is invalid.");
+      return (ARCHIVE_FATAL);
+    }
     new_window = realloc(rar->lzss.window, new_size);
     if (new_window == NULL) {
       archive_set_error(&a->archive, ENOMEM,
-- 
2.17.1