From: Szabolcs Nagy <szabolcs.nagy@arm.com>
Date: Thu, 11 Mar 2021 14:09:56 +0000 (+0000)
Subject: malloc: Fix a potential realloc issue with memory tagging
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=83efe3b3d2aa419f6a45828de9c38341acbf8ac3;p=thirdparty%2Fglibc.git

malloc: Fix a potential realloc issue with memory tagging

At an _int_free call site in realloc the wrong size was used for tag
clearing: the chunk header of the next chunk was also cleared which
in practice may work, but logically wrong.

The tag clearing is moved before the memcpy to save a tag computation,
this avoids a chunk2mem.  Another chunk2mem is removed because newmem
does not have to be recomputed. Whitespaces got fixed too.
---

diff --git a/malloc/malloc.c b/malloc/malloc.c
index 8f8f12c2768..51cec67e559 100644
--- a/malloc/malloc.c
+++ b/malloc/malloc.c
@@ -4851,14 +4851,14 @@ _int_realloc(mstate av, mchunkptr oldp, INTERNAL_SIZE_T oldsize,
             }
           else
             {
-	      void *oldmem = chunk2mem (oldp);
+	      void *oldmem = chunk2rawmem (oldp);
+	      size_t sz = CHUNK_AVAILABLE_SIZE (oldp) - CHUNK_HDR_SZ;
+	      (void) TAG_REGION (oldmem, sz);
 	      newmem = TAG_NEW_USABLE (newmem);
-	      memcpy (newmem, oldmem,
-		      CHUNK_AVAILABLE_SIZE (oldp) - CHUNK_HDR_SZ);
-	      (void) TAG_REGION (chunk2rawmem (oldp), oldsize);
-              _int_free (av, oldp, 1);
-              check_inuse_chunk (av, newp);
-              return chunk2mem (newp);
+	      memcpy (newmem, oldmem, sz);
+	      _int_free (av, oldp, 1);
+	      check_inuse_chunk (av, newp);
+	      return newmem;
             }
         }
     }