commit 98bb18f52a7c576e6068f4b42dea5b24fa6fd81e
Author: Szabolcs Nagy <szabolcs.nagy@arm.com>
Date:   Thu Feb 25 14:49:58 2021 +0000

    malloc: Fix a realloc crash with heap tagging [BZ 27468]
    
    _int_free must be called with a chunk that has its tag reset. This was
    missing in a rare case that could crash when heap tagging is enabled:
    when in a multi-threaded process the current arena runs out of memory
    during realloc, but another arena still has space to finish the realloc
    then _int_free was called without clearing the user allocation tags.
    
    Fixes bug 27468.
    
    Reviewed-by: DJ Delorie <dj@redhat.com>
    (cherry picked from commit 42cc96066b22ba065db11096c78881a55e45def4)

diff --git a/malloc/malloc.c b/malloc/malloc.c
index 1f4bbd8edf8b9770..8f8f12c276812405 100644
--- a/malloc/malloc.c
+++ b/malloc/malloc.c
@@ -3446,7 +3446,9 @@ __libc_realloc (void *oldmem, size_t bytes)
       newp = __libc_malloc (bytes);
       if (newp != NULL)
         {
-          memcpy (newp, oldmem, oldsize - SIZE_SZ);
+	  size_t sz = CHUNK_AVAILABLE_SIZE (oldp) - CHUNK_HDR_SZ;
+	  memcpy (newp, oldmem, sz);
+	  (void) TAG_REGION (chunk2rawmem (oldp), sz);
           _int_free (ar_ptr, oldp, 0);
         }
     }