malloc: Always call memcpy in _int_realloc [BZ #24027]

This commit removes the custom memcpy implementation from _int_realloc
for small chunk sizes.  The ncopies variable has the wrong type, and
an integer wraparound could cause the existing code to copy too few
elements (leaving the new memory region mostly uninitialized).
Therefore, removing this code fixes bug 24027.

(cherry picked from commit b50dd3bc8cbb1efe85399b03d7e6c0310c2ead84)

diff --git a/ChangeLog b/ChangeLog
index 2d3af62685c00bc76624b60eb1825ee829e71044..b5727c7585c55ee97387fae9f8315702b4359c94 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+2018-12-31  Florian Weimer  <fw@deneb.enyo.de>
+
+       [BZ #24027]
+       * malloc/malloc.c (_int_realloc): Always call memcpy for the
+       copying operation.  (ncopies had the wrong type, resulting in an
+       integer wraparound and too few elements being copied.)
+
 2018-11-27  Florian Weimer  <fweimer@redhat.com>
 
        [BZ #23927]

diff --git a/NEWS b/NEWS
index f6d26425ffae67e5d4f6ec0312b458cdd382692b..ef857b6e6cebf5afe12fd434075e53fe3446a401 100644 (file)
--- a/NEWS
+++ b/NEWS
@@ -163,6 +163,7 @@ The following bugs are resolved with this release:
   [23579] libc: Errors misreported in preadv2
   [23709] Fix CPU string flags for Haswell-type CPUs
   [23927] Linux if_nametoindex() does not close descriptor (CVE-2018-19591)
+  [24027] malloc: Integer overflow in realloc
 \f
 Version 2.26
 

diff --git a/malloc/malloc.c b/malloc/malloc.c
index 862337466eba519db2670197f460e134c8984816..49e8ed69c2697d8fb1a71c070d803356bfe91c63 100644 (file)
--- a/malloc/malloc.c
+++ b/malloc/malloc.c
@@ -4528,11 +4528,6 @@ _int_realloc(mstate av, mchunkptr oldp, INTERNAL_SIZE_T oldsize,
   mchunkptr        bck;             /* misc temp for linking */
   mchunkptr        fwd;             /* misc temp for linking */
 
-  unsigned long    copysize;        /* bytes to copy */
-  unsigned int     ncopies;         /* INTERNAL_SIZE_T words to copy */
-  INTERNAL_SIZE_T* s;               /* copy source */
-  INTERNAL_SIZE_T* d;               /* copy destination */
-
   /* oldmem size */
   if (__builtin_expect (chunksize_nomask (oldp) <= 2 * SIZE_SZ, 0)
       || __builtin_expect (oldsize >= av->system_mem, 0))
@@ -4600,43 +4595,7 @@ _int_realloc(mstate av, mchunkptr oldp, INTERNAL_SIZE_T oldsize,
             }
           else
             {
-              /*
-                 Unroll copy of <= 36 bytes (72 if 8byte sizes)
-                 We know that contents have an odd number of
-                 INTERNAL_SIZE_T-sized words; minimally 3.
-               */
-
-              copysize = oldsize - SIZE_SZ;
-              s = (INTERNAL_SIZE_T *) (chunk2mem (oldp));
-              d = (INTERNAL_SIZE_T *) (newmem);
-              ncopies = copysize / sizeof (INTERNAL_SIZE_T);
-              assert (ncopies >= 3);
-
-              if (ncopies > 9)
-                memcpy (d, s, copysize);
-
-              else
-                {
-                  *(d + 0) = *(s + 0);
-                  *(d + 1) = *(s + 1);
-                  *(d + 2) = *(s + 2);
-                  if (ncopies > 4)
-                    {
-                      *(d + 3) = *(s + 3);
-                      *(d + 4) = *(s + 4);
-                      if (ncopies > 6)
-                        {
-                          *(d + 5) = *(s + 5);
-                          *(d + 6) = *(s + 6);
-                          if (ncopies > 8)
-                            {
-                              *(d + 7) = *(s + 7);
-                              *(d + 8) = *(s + 8);
-                            }
-                        }
-                    }
-                }
-
+             memcpy (newmem, chunk2mem (oldp), oldsize - SIZE_SZ);
               _int_free (av, oldp, 1);
               check_inuse_chunk (av, newp);
               return chunk2mem (newp);