Fwd: New Defects reported by Coverity Scan for git

[Stefan Beller <sbeller@google.com>]

I looked at this report for a while. My current understanding:
* its detection was triggered by including rs/move-array,
  f331ab9d4c (use MOVE_ARRAY, 2017-07-15)
* But it is harmless, because the scan logic does not understand
  how ALLOC_GROW works. It assumes that
  done_pbase_paths_alloc can be larger
  than done_pbase_paths_num + 1, while done_pbase_paths
  is NULL, such that the memory allocation is not triggered.
  If that were the case, then we have 2 subsequent dereferences
  of a NULL pointer right after that. But by inspecting the use
  of _alloc and _num the initial assumption does not seem possible.

Stefan

---------- Forwarded message ----------
From:  <scan-admin@coverity.com>
Date: Tue, Jul 18, 2017 at 2:53 AM
Subject: New Defects reported by Coverity Scan for git
To: sbeller@google.com



Hi,

Please find the latest report on new defect(s) introduced to git found
with Coverity Scan.

2 new defect(s) introduced to git found with Coverity Scan.
1 defect(s), reported by Coverity Scan earlier, were marked fixed in
the recent build analyzed by Coverity Scan.

New defect(s) Reported-by: Coverity Scan
Showing 2 of 2 defect(s)


** CID 1415508:  Null pointer dereferences  (FORWARD_NULL)
/builtin/pack-objects.c: 1292 in check_pbase_path()


________________________________________________________________________________________________________
*** CID 1415508:  Null pointer dereferences  (FORWARD_NULL)
/builtin/pack-objects.c: 1292 in check_pbase_path()
1286            }
1287            return -lo-1;
1288     }
1289
1290     static int check_pbase_path(unsigned hash)
1291     {
>>>     CID 1415508:  Null pointer dereferences  (FORWARD_NULL)
>>>     Comparing "done_pbase_paths" to null implies that "done_pbase_paths" might be null.
1292            int pos = (!done_pbase_paths) ? -1 : done_pbase_path_pos(hash);
1293            if (0 <= pos)
1294                    return 1;
1295            pos = -pos - 1;
1296            ALLOC_GROW(done_pbase_paths,
1297                       done_pbase_paths_num + 1,

** CID 1415507:  Null pointer dereferences  (FORWARD_NULL)
/builtin/pack-objects.c: 1303 in check_pbase_path()


________________________________________________________________________________________________________
*** CID 1415507:  Null pointer dereferences  (FORWARD_NULL)
/builtin/pack-objects.c: 1303 in check_pbase_path()
1297                       done_pbase_paths_num + 1,
1298                       done_pbase_paths_alloc);
1299            done_pbase_paths_num++;
1300            if (pos < done_pbase_paths_num)
1301                    MOVE_ARRAY(done_pbase_paths + pos + 1,
done_pbase_paths + pos,
1302                               done_pbase_paths_num - pos - 1);
>>>     CID 1415507:  Null pointer dereferences  (FORWARD_NULL)
>>>     Dereferencing null pointer "done_pbase_paths".
1303            done_pbase_paths[pos] = hash;
1304            return 0;
1305     }
1306
1307     static void add_preferred_base_object(const char *name)
1308     {


________________________________________________________________________________________________________
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