iemejia commented on code in PR #3864:
URL: https://github.com/apache/avro/pull/3864#discussion_r3565772881
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lang/perl/lib/Avro/BinaryDecoder.pm:
##########
@@ -124,18 +124,130 @@ sub skip_bytes {
my $class = shift;
my $reader = pop;
my $size = decode_long($class, undef, undef, $reader);
- $reader->seek($size, 0);
+ if ($size < 0) {
+ throw Avro::Schema::Error::Parse(
+ "Invalid negative bytes/string length: $size");
+ }
+ # Skip forward by $size bytes relative to the current position
+ # (SEEK_CUR); whence 0 (SEEK_SET) would incorrectly seek to the
+ # absolute offset $size.
+ $reader->seek($size, 1);
return;
Review Comment:
Fixed in 25ab8ab266: skip_bytes now calls _ensure_available before skipping
(mirroring decode_bytes), so a declared length that exceeds the remaining bytes
is rejected on a size-reporting reader instead of silently seeking past EOF,
and a failed seek is treated as fatal.
While here I fixed the same absolute-vs-relative seek bug in two related
paths that shared it: skip_fixed used seek(size, 0) (SEEK_SET) — now SEEK_CUR —
and skip_block's negative-count branch ignored the block-size long, did an
absolute seek of a negative offset, and re-looped on the same count (an
infinite loop); it now reads the block size and skips it relatively. Added
tests for skipping fixed/bytes writer fields absent from the reader schema and
for rejecting an oversized skipped bytes length. Full suite (386 tests) and
perlcritic pass.
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