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Initialize padding bytes in btree_gist varbit support.

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The code expands a varbit gist leaf key to a node key by copying the bit
data twice in a varlen datum, as both the lower and upper key. The lower key
was expanded to INTALIGN size, but the padding bytes were not initialized.
That's a problem because when the lower/upper keys are compared, the padding
bytes are used compared too, when the values are otherwise equal. That could
lead to incorrect query results.

REINDEX is advised for any btree_gist indexes on bit or bit varying data
type, to fix any garbage padding bytes on disk.

Per Valgrind, reported by Andres Freund. Backpatch to all supported
versions.
This commit is contained in:
Heikki Linnakangas 2014-05-13 14:16:28 +03:00
parent b65a258a51
commit d5b912c905
1 changed files with 7 additions and 3 deletions
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10
contrib/btree_gist/btree_bit.c
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@ -83,10 +83,14 @@ static bytea *
gbt_bit_xfrm(bytea *leaf) gbt_bit_xfrm(bytea *leaf)
{ {
bytea *out = leaf; bytea *out = leaf;
int s = INTALIGN(VARBITBYTES(leaf) + VARHDRSZ); int sz = VARBITBYTES(leaf) + VARHDRSZ;
int padded_sz = INTALIGN(sz);
out = palloc(s); out = (bytea *) palloc(padded_sz);
SET_VARSIZE(out, s); /* initialize the padding bytes to zero */
while (sz < padded_sz)
((char *) out)[sz++] = 0;
SET_VARSIZE(out, padded_sz);
memcpy((void *) VARDATA(out), (void *) VARBITS(leaf), VARBITBYTES(leaf)); memcpy((void *) VARDATA(out), (void *) VARBITS(leaf), VARBITBYTES(leaf));
return out; return out;
} }