Copilot commented on code in PR #3853:
URL: https://github.com/apache/avro/pull/3853#discussion_r3567560534
##########
lang/c/src/codec.c:
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@@ -483,11 +609,41 @@ 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.
Review Comment:
`decode_lzma` passes the `int64_t len` parameter directly to
`lzma_raw_buffer_decode` as the input size. Since liblzma takes a `size_t` for
that argument, a negative (or >SIZE_MAX) `len` passed to `avro_codec_decode()`
would wrap/truncate during implicit conversion and could make the decoder read
an unintended amount of input. Add an explicit range check and cast once to a
local `size_t` before calling into liblzma.
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