Check for empty buffer when rendering #254
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For empty documents, `->size` is zero so `renderer.buffer->ptr[renderer.buffer->size - 1]` will cause an out-of-bounds read. Empty buffers always point to the global `cmark_strbuf__initbuf` buffer so we read `cmark_strbuf__initbuf[-1]`.
We currently discard fuzz test-cases that are empty but empty inputs are valid markdown. This improves the fuzzing coverage slightly.
Allow the `width` parameter to be generated too so we get better fuzz-coverage.
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Belated thanks! |
talum
referenced
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in github/cmark-gfm
Sep 14, 2021
Check for empty buffer when rendering
QuietMisdreavus
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to swiftlang/swift-cmark
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Apr 6, 2023
…ent_footnote_def Expose `cmark_node_parent_footnote_def`.
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This minor bug came in via GitHub's Bug Bounty program. I did some digging and we didn't find this bug via fuzzing because we discard all empty documents in
test/cmark-fuzz.c. I tweaked the fuzzing harness to accept empty documents.I also noticed we use a fixed width when fuzzing. Allow the
widthparameter to be fuzzed too for better coverage.