[PATCH v5 0/3] Add commit-graph fuzzer and fix buffer overflow

[Josh Steadmon <steadmon@google.com>]

Add a new fuzz test for the commit graph and fix a buffer read-overflow
that it discovered. Additionally, fix the Makefile instructions for
building fuzzers.

Changes since V4:
  * Ensure that corrupt_graph_and_verify() in t5318 changes to the
    proper directory before accessing any files.

Changes since V3:
  * Improve portability of the new test functionality.
  * Fix broken &&-chains in tests.

Changes since V2:
  * Avoid pointer arithmetic overflow when checking the graph's chunk
    count.
  * Merge the corrupt_graph_and_verify and
    corrupt_and_zero_graph_then_verify test functions.

Josh Steadmon (3):
  commit-graph, fuzz: Add fuzzer for commit-graph
  commit-graph: fix buffer read-overflow
  Makefile: correct example fuzz build

Josh Steadmon (3):
  commit-graph, fuzz: Add fuzzer for commit-graph
  commit-graph: fix buffer read-overflow
  Makefile: correct example fuzz build

 .gitignore              |  1 +
 Makefile                |  3 +-
 commit-graph.c          | 67 +++++++++++++++++++++++++++++------------
 commit-graph.h          |  3 ++
 fuzz-commit-graph.c     | 16 ++++++++++
 t/t5318-commit-graph.sh | 16 ++++++++--
 6 files changed, 83 insertions(+), 23 deletions(-)
 create mode 100644 fuzz-commit-graph.c

Range-diff against v4:
1:  80b5662f30 ! 1:  a3b5d33c4b commit-graph: fix buffer read-overflow
    @@ -52,12 +52,12 @@
      # and places the output in the file 'err'. Test 'err' for
      # the given string.
      corrupt_graph_and_verify() {
    - 	pos=$1
    +@@
      	data="${2:-\0}"
      	grepstr=$3
    + 	cd "$TRASH_DIRECTORY/full" &&
     +	orig_size=$(wc -c < $objdir/info/commit-graph) &&
     +	zero_pos=${4:-${orig_size}} &&
    - 	cd "$TRASH_DIRECTORY/full" &&
      	test_when_finished mv commit-graph-backup $objdir/info/commit-graph &&
      	cp $objdir/info/commit-graph commit-graph-backup &&
      	printf "$data" | dd of="$objdir/info/commit-graph" bs=1 seek="$pos" conv=notrunc &&
2:  21101b961a = 2:  350ea5f7c9 Makefile: correct example fuzz build
-- 
2.20.1.97.g81188d93c3-goog