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Second thoughts on TOAST decompression.

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On detecting a corrupted match tag, pglz_decompress() should just
summarily return -1.  Breaking out of the loop, as I did in dfc797730,
doesn't quite guarantee that will happen.  Also, we can use
unlikely() on that check, just in case it helps.

Backpatch to v13, like the previous patch.
This commit is contained in:
Tom Lane 2020-11-02 11:25:18 -05:00
parent 57fae192f8
commit 7957e75c58
1 changed files with 9 additions and 8 deletions
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17
src/common/pg_lzcompress.c
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@ -680,9 +680,12 @@ pglz_compress(const char *source, int32 slen, char *dest,
* pglz_decompress -
*
* Decompresses source into dest. Returns the number of bytes
* decompressed in the destination buffer, and *optionally*
* checks that both the source and dest buffers have been
* fully read and written to, respectively.
* decompressed into the destination buffer, or -1 if the
* compressed data is corrupted.
*
* If check_complete is true, the data is considered corrupted
* if we don't exactly fill the destination buffer. Callers that
* are extracting a slice typically can't apply this check.
* ----------
*/
int32
@ -736,8 +739,8 @@ pglz_decompress(const char *source, int32 slen, char *dest,
* must check this, else we risk an infinite loop below in the
* face of corrupt data.)
*/
if (sp > srcend || off == 0)
break;
if (unlikely(sp > srcend || off == 0))
return -1;
/*
* Don't emit more data than requested.
@ -809,9 +812,7 @@ pglz_decompress(const char *source, int32 slen, char *dest,
}
/*
* Check we decompressed the right amount. If we are slicing, then we
* won't necessarily be at the end of the source or dest buffers when we
* hit a stop, so we don't test them.
* If requested, check we decompressed the right amount.
*/
if (check_complete && (dp != destend || sp != srcend))
return -1;