iemejia commented on code in PR #3853:
URL: https://github.com/apache/avro/pull/3853#discussion_r3567475343
##########
lang/c/src/codec.c:
##########
@@ -483,11 +598,38 @@ static int decode_lzma(avro_codec_t codec, void * data,
int64_t len)
codec->used_size = write_pos;
- // If it ran out of space to decode, give it more!!
- // It will continue where it left off because of read_pos and
write_pos.
+ // Reject a block that decompresses to more than the allowed
maximum,
+ // to guard against unbounded allocation from a high-ratio
block.
+ if ((int64_t) write_pos > max_len) {
+ avro_set_error("Decompressed block size exceeds the
maximum allowed of %lld bytes",
+ (long long) max_len);
+ return 1;
+ }
Review Comment:
Fixed — the guard now compares `write_pos > (size_t) max_len` (max_len is >=
0 and clamped to SIZE_MAX) instead of narrowing write_pos to int64_t, so it
can't wrap negative and bypass the cap.
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