Copilot commented on code in PR #3853:
URL: https://github.com/apache/avro/pull/3853#discussion_r3568129129
##########
lang/c/src/codec.c:
##########
@@ -141,12 +188,29 @@ static int decode_snappy(avro_codec_t c, void * data,
int64_t len)
{
uint32_t crc;
size_t outlen;
+ int64_t max_len = avro_max_decompress_length();
+
+ /* The block carries a trailing 4-byte CRC; a length below that is
+ * malformed and would underflow len - 4. */
+ if (len < 4) {
+ avro_set_error("Snappy block too small (%lld bytes), expected
at least 4",
+ (long long) len);
Review Comment:
decode_snappy validates len >= 4, but still passes `len-4` (int64_t) to
Snappy APIs that take `size_t`, and also uses `len-4` in pointer arithmetic
later. On 32-bit (or any platform where `len-4` can exceed `SIZE_MAX`), this
will truncate during implicit conversion and can lead to out-of-bounds
reads/crashes. Add an explicit range check that `len-4` fits in `size_t`, and
use a single `size_t inlen = (size_t)(len-4)` for all Snappy calls and CRC
offset computations.
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