Add additional sanity checks when reading a blkreftable.

Code elsewhere in the system assumes that fork numbers and chunk sizes
are within bounds, so the code that reads those quantities from disk
should validate that they are. Without these additional checks, a
corrupted file can cause us to index off the end of fork number or chunk
entry arrays, potentially resulting in a crash.

Reported-by: oxsignal <awo@kakao.com> (chunk sizes)
Reported-by: Robert Haas <rhaas@postgresql.org> (fork numbers)
Reviewed-by: Daniel Gustafsson <daniel@yesql.se>
Discussion: http://postgr.es/m/CA+TgmoYP8RKoBGosS7C6Fdr-GNCfyz_W1zmK=Tx1Fe0ZvzGh0g@mail.gmail.com
Backpatch-through: 17

diff --git a/src/common/blkreftable.c b/src/common/blkreftable.c
index 2bb91e391282161cf6a9e886ecde816566e83d36..a166fcc0067c92975ec767fd18ee9feab1e92819 100644 (file)
--- a/src/common/blkreftable.c
+++ b/src/common/blkreftable.c
@@ -657,6 +657,15 @@ BlockRefTableReaderNextRelation(BlockRefTableReader *reader,
                return false;
        }
 
+       /* Sanity-check the fork number. */
+       if (sentry.forknum < 0 || sentry.forknum > MAX_FORKNUM)
+       {
+               reader->error_callback(reader->error_callback_arg,
+                                                          "file \"%s\" has invalid fork number %d",
+                                                          reader->error_filename, sentry.forknum);
+               return false;
+       }
+
        /*
         * Sanity-check the nchunks value.  In the backend, palloc_array would
         * enforce this anyway (with a more generic error message); but in
@@ -678,6 +687,19 @@ BlockRefTableReaderNextRelation(BlockRefTableReader *reader,
        BlockRefTableRead(reader, reader->chunk_size,
                                          sentry.nchunks * sizeof(uint16));
 
+       /* Sanity-check the chunk sizes. */
+       for (unsigned i = 0; i < sentry.nchunks; ++i)
+       {
+               if (reader->chunk_size[i] > MAX_ENTRIES_PER_CHUNK)
+               {
+                       reader->error_callback(reader->error_callback_arg,
+                                                                  "file \"%s\" chunk %u has invalid size %u",
+                                                                  reader->error_filename, i,
+                                                                  (unsigned) reader->chunk_size[i]);
+                       return false;
+               }
+       }
+
        /* Set up for chunk scan. */
        reader->total_chunks = sentry.nchunks;
        reader->consumed_chunks = 0;