From: Daniel Axtens <dja@axtens.net>
Date: Wed, 20 Jan 2021 13:05:58 +0000 (+1100)
Subject: io/gzio: Add init_dynamic_block() clean up if unpacking codes fails
X-Git-Tag: grub-2.06-rc1~60
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=18490336d91da2b532277cba56473bfed1376fc4;p=thirdparty%2Fgrub.git

io/gzio: Add init_dynamic_block() clean up if unpacking codes fails

init_dynamic_block() didn't clean up gzio->tl and td in some error
paths. This left td pointing to part of tl. Then in grub_gzio_close(),
when tl was freed the storage for td would also be freed. The code then
attempts to free td explicitly, performing a UAF and then a double free.

Explicitly clean up tl and td in the error paths.

Signed-off-by: Daniel Axtens <dja@axtens.net>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
---

diff --git a/grub-core/io/gzio.c b/grub-core/io/gzio.c
index 4a8eaeae2..4236f0fd4 100644
--- a/grub-core/io/gzio.c
+++ b/grub-core/io/gzio.c
@@ -953,7 +953,7 @@ init_dynamic_block (grub_gzio_t gzio)
 	  if ((unsigned) i + j > n)
 	    {
 	      grub_error (GRUB_ERR_BAD_COMPRESSED_DATA, "too many codes found");
-	      return;
+	      goto fail;
 	    }
 	  while (j--)
 	    ll[i++] = l;
@@ -966,7 +966,7 @@ init_dynamic_block (grub_gzio_t gzio)
 	  if ((unsigned) i + j > n)
 	    {
 	      grub_error (GRUB_ERR_BAD_COMPRESSED_DATA, "too many codes found");
-	      return;
+	      goto fail;
 	    }
 	  while (j--)
 	    ll[i++] = 0;
@@ -981,7 +981,7 @@ init_dynamic_block (grub_gzio_t gzio)
 	  if ((unsigned) i + j > n)
 	    {
 	      grub_error (GRUB_ERR_BAD_COMPRESSED_DATA, "too many codes found");
-	      return;
+	      goto fail;
 	    }
 	  while (j--)
 	    ll[i++] = 0;
@@ -1019,6 +1019,12 @@ init_dynamic_block (grub_gzio_t gzio)
   /* indicate we're now working on a block */
   gzio->code_state = 0;
   gzio->block_len++;
+  return;
+
+ fail:
+  huft_free (gzio->tl);
+  gzio->td = NULL;
+  gzio->tl = NULL;
 }