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fuzz: v8 page targets that reach their decoders; keep the corpus between runs (#387, #375) #498

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adityamukho merged 1 commit into from
Oct 9, 2026
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fuzz: v8 page targets that reach their decoders; keep the corpus between runs (#387, #375) #498

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179 changes: 179 additions & 0 deletions .github/workflows/fuzz-corpus.yml
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name: Fuzz corpus (weekly)

# Minimizes each target's cached fuzz corpus (see fuzz.yml) with
# `cargo fuzz cmin`, saves the result back to the cache, and proposes it as a
# commit to the branch in a pull request from bot/fuzz-corpus-<branch> (#387).
# Committed seed_* files are always kept: they are regression seeds.
#
# Two branches, as in fuzz.yml: main on Monday 08:00 UTC, v3 on Monday 20:00
# UTC. Keep the cron strings here and in CORPUS_REF/run-name identical, and
# keep this file the same on main and v3.
#
# Opening the pull request needs the repository setting "Allow GitHub Actions
# to create and approve pull requests". Without it, the branch is still
# pushed and the job summary links to it. Pull requests opened with
# GITHUB_TOKEN do not start CI; they change only fuzz/corpus/.
run-name: >-
Fuzz corpus (${{ github.event_name == 'workflow_dispatch' && inputs.ref
|| (github.event.schedule == '0 20 * * 1' && 'v3' || 'main') }})

on:
schedule:
- cron: "0 8 * * 1" # main
- cron: "0 20 * * 1" # v3
workflow_dispatch:
inputs:
ref:
description: Branch whose corpus to minimize
required: true
default: main

permissions:
contents: read

env:
CORPUS_REF: ${{ github.event_name == 'workflow_dispatch' && inputs.ref || (github.event.schedule == '0 20 * * 1' && 'v3' || 'main') }}
# Larger corpus files stay in the cache only.
MAX_COMMITTED_BYTES: "65536"

jobs:
targets:
name: List fuzz targets
runs-on: ubuntu-latest
outputs:
targets: ${{ steps.list.outputs.targets }}
steps:
- uses: actions/checkout@v4
with:
ref: ${{ env.CORPUS_REF }}

- name: Read the [[bin]] names
id: list
shell: bash
run: |
targets="$(sed -n 's/^name = "\(.*\)"$/\1/p' fuzz/Cargo.toml | grep -vx minigraf-fuzz \
| jq -R . | jq -sc .)"
echo "targets=$targets" >> "$GITHUB_OUTPUT"

cmin:
name: Minimize ${{ matrix.target }}
needs: targets
runs-on: ubuntu-latest
timeout-minutes: 60
strategy:
fail-fast: false
matrix:
target: ${{ fromJSON(needs.targets.outputs.targets) }}

steps:
- uses: actions/checkout@v4
with:
ref: ${{ env.CORPUS_REF }}

- name: Install Rust nightly
uses: dtolnay/rust-toolchain@nightly

- name: Cache cargo-fuzz binary
uses: actions/cache@v4
with:
path: ~/.cargo/bin/cargo-fuzz
key: cargo-fuzz-${{ runner.os }}-${{ hashFiles('fuzz/Cargo.toml') }}

- name: Install cargo-fuzz
run: which cargo-fuzz || cargo install cargo-fuzz

- name: Restore corpus
uses: actions/cache/restore@v4
with:
path: fuzz/corpus/${{ matrix.target }}
key: fuzz-corpus-${{ env.CORPUS_REF }}-${{ matrix.target }}-cmin-${{ github.run_id }}-${{ github.run_attempt }}
restore-keys: fuzz-corpus-${{ env.CORPUS_REF }}-${{ matrix.target }}-

- name: Minimize
shell: bash
env:
TARGET: ${{ matrix.target }}
run: |
dir="fuzz/corpus/$TARGET"
echo "Before: $(find "$dir" -type f | wc -l) files"
cargo fuzz cmin -O "$TARGET" "$dir"
# Put back every committed seed cmin dropped.
git ls-files -z "$dir" | grep -z '/seed_' | xargs -0 -r git checkout --
echo "After: $(find "$dir" -type f | wc -l) files"

- name: Save corpus
uses: actions/cache/save@v4
with:
path: fuzz/corpus/${{ matrix.target }}
key: fuzz-corpus-${{ env.CORPUS_REF }}-${{ matrix.target }}-cmin-${{ github.run_id }}-${{ github.run_attempt }}

- name: Keep committable files
shell: bash
env:
TARGET: ${{ matrix.target }}
run: |
mkdir -p "committed/$TARGET"
find "fuzz/corpus/$TARGET" -maxdepth 1 -type f -size -"$((MAX_COMMITTED_BYTES + 1))"c \
-exec cp {} "committed/$TARGET/" \;

- uses: actions/upload-artifact@v4
with:
name: corpus-${{ matrix.target }}
path: committed/
retention-days: 7

propose:
name: Propose the minimized corpus
needs: cmin
runs-on: ubuntu-latest
permissions:
contents: write
pull-requests: write
steps:
- uses: actions/checkout@v4
with:
ref: ${{ env.CORPUS_REF }}

- uses: actions/download-artifact@v4
with:
pattern: corpus-*
path: minimized
merge-multiple: true

- name: Commit, push and open the pull request
shell: bash
env:
GH_TOKEN: ${{ github.token }}
run: |
branch="bot/fuzz-corpus-$CORPUS_REF"
for d in minimized/*/; do
target="$(basename "$d")"
rm -rf "fuzz/corpus/$target"
cp -r "$d" "fuzz/corpus/$target"
done
git add -A fuzz/corpus
if git diff --cached --quiet; then
echo "Corpus unchanged." | tee -a "$GITHUB_STEP_SUMMARY"
exit 0
fi
git config user.name "github-actions[bot]"
git config user.email "41898282+github-actions[bot]@users.noreply.github.com"
git commit -q -m "fuzz: minimized corpus for $CORPUS_REF (weekly cmin)" \
-m "Run: $GITHUB_SERVER_URL/$GITHUB_REPOSITORY/actions/runs/$GITHUB_RUN_ID" \
-m "Refs #387"
git push -f origin "HEAD:refs/heads/$branch"

body="Weekly \`cargo fuzz cmin\` of the cached corpus of every fuzz target on \`$CORPUS_REF\`, with all committed \`seed_*\` files kept. Files over $MAX_COMMITTED_BYTES bytes stay in the cache only. Generated by \`.github/workflows/fuzz-corpus.yml\` (#387).

Run: $GITHUB_SERVER_URL/$GITHUB_REPOSITORY/actions/runs/$GITHUB_RUN_ID"
existing="$(gh pr list --head "$branch" --base "$CORPUS_REF" --state open --json number --jq '.[0].number')"
if [ -n "$existing" ]; then
echo "Updated pull request #$existing." | tee -a "$GITHUB_STEP_SUMMARY"
elif gh pr create --base "$CORPUS_REF" --head "$branch" \
--title "fuzz: minimized corpus for $CORPUS_REF" --body "$body"; then
echo "Opened a pull request from $branch." | tee -a "$GITHUB_STEP_SUMMARY"
else
compare="$GITHUB_SERVER_URL/$GITHUB_REPOSITORY/compare/$CORPUS_REF...$branch?expand=1"
echo "Could not open the pull request (is \"Allow GitHub Actions to create and approve pull requests\" off?). Open it from $compare" \
| tee -a "$GITHUB_STEP_SUMMARY"
fi
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