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[C] Fix negative block size validation in datafile reader #3623

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[C] Fix negative block size validation in datafile reader #3623

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68e67d5
[C] Fix negative block size validation in datafile reader
OwenSanzas Jan 13, 2026
5107a18
Add NULL checks after malloc/realloc in file_read_block_count
OwenSanzas Jan 14, 2026
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12 changes: 12 additions & 0 deletions lang/c/src/datafile.c
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Original file line number Diff line number Diff line change
Expand Up @@ -451,12 +451,24 @@ static int file_read_block_count(avro_file_reader_t r)
"Cannot read file block count: ");
check_prefix(rval, enc->read_long(r->reader, &len),
"Cannot read file block size: ");
if (len < 0) {
avro_set_error("Invalid block size: %" PRId64, len);
return EINVAL;
}
Comment on lines +454 to +457
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Copilot AI Jan 13, 2026

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Consider adding a regression test that verifies the negative block size validation. While the fix was verified with AddressSanitizer fuzzing, a unit test with a malformed Avro file containing a negative block size would help prevent regressions. This could follow the pattern of other test files like test_avro_1237.c which test handling of malformed Avro files.

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if (r->current_blockdata && len > r->current_blocklen) {
r->current_blockdata = (char *) avro_realloc(r->current_blockdata, r->current_blocklen, len);
if (!r->current_blockdata) {
avro_set_error("Cannot allocate block buffer");
return ENOMEM;
}
r->current_blocklen = len;
} else if (!r->current_blockdata) {
r->current_blockdata = (char *) avro_malloc(len);
if (!r->current_blockdata && len > 0) {
avro_set_error("Cannot allocate block buffer");
return ENOMEM;
}
r->current_blocklen = len;
}

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