dfc797730f
pglz_maximum_compressed_size() potentially underestimated the amount of compressed data required to produce N bytes of decompressed data; this is a fault in commit 11a078cf8. Separately from that, pglz_decompress() failed to protect itself against corrupt compressed data, particularly off == 0 in a match tag. Commit c60e520f6 turned such a situation into an infinite loop, where before it'd just have resulted in garbage output. The combination of these two bugs seems like it may explain bug #16694 from Tom Vijlbrief, though it's impossible to be quite sure without direct inspection of the failing session. (One needs to assume that the pglz_maximum_compressed_size() bug caused us to fail to fetch the second byte of a match tag, and what happened to be there instead was a zero. The reported infinite loop is hard to explain without off == 0, though.) Aside from fixing the bugs, rewrite associated comments for more clarity. Back-patch to v13 where both these commits landed. Discussion: https://postgr.es/m/16694-f107871e499ec114@postgresql.org
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