[PATCH v4 0/3] sparse-checkout: fix segfault on malformed patterns

This series fixes some issues with parsing sparse-checkout patterns when core.sparseCheckoutCone is enabled but the sparse-checkout file itself contains patterns that don't match the cone mode format.

The first patch fixes a segfault first reported in [1]. The other two patches are from an earlier submission [2] that never got picked up and I lost track of. There was another patch involving 'git sparse-checkout init --cone' that isn't necessary, especially with Elijah doing some work in that space right now.

[1] https://github.com/git-for-windows/git/issues/3498 [2] https://lore.kernel.org/git/pull.1043.git.1632160658.gitgitgadget@gmail.com

Thanks, -Stolee

Update in v4 ============

 * For added precaution, this kind of unexpected duplicate pattern will
   disable cone mode matching.
 * Tests are updated to verify this new behavior.

Updates in v2 and v3 ====================

 * I intended to fix a typo in a patch, but accidentally sent the amend!
   commit in v2
 * v3 has the typo fix properly squashed in.
 * Added Elijah's review.

Derrick Stolee (3):
  sparse-checkout: fix segfault on malformed patterns
  sparse-checkout: fix OOM error with mixed patterns
  sparse-checkout: refuse to add to bad patterns

 builtin/sparse-checkout.c          |  5 +++-
 dir.c                              |  6 ++---
 t/t1091-sparse-checkout-builtin.sh | 37 +++++++++++++++++++++++++++++-
 3 files changed, 42 insertions(+), 6 deletions(-)

base-commit: abe6bb3905392d5eb6b01fa6e54d7e784e0522aa
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1069%2Fderrickstolee%2Fsparse-checkout%2Finput-bug-v4
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1069/derrickstolee/sparse-checkout/input-bug-v4
Pull-Request: https://github.com/gitgitgadget/git/pull/1069

Range-diff vs v3:

 1:  1744a26845f ! 1:  5353c541d9f sparse-checkout: fix segfault on malformed patterns
     @@ Commit message
          list' command because it iterates over the contents of the hashset, which is
          now invalid.
      
     -    The fix here is to stop trying to remove from the hashset. Better to leave
     -    bad data in the sparse-checkout matching logic (with a warning) than to
     -    segfault. If we are in this state, then we are already traversing into
     -    undefined behavior, so this change to keep the entry in the hashset is no
     -    worse than removing it.
     +    The fix here is to stop trying to remove from the hashset. In addition,
     +    we disable cone mode sparse-checkout because of the malformed data. This
     +    results in the pattern-matching working with a possibly-slower
     +    algorithm, but using the patterns as they are in the sparse-checkout
     +    file.
     +
     +    This also changes the behavior of commands such as 'git sparse-checkout
     +    list' because the output patterns will be the contents of the
     +    sparse-checkout file instead of the list of directories. This is an
     +    existing behavior for other types of bad patterns.
      
          Add a test that triggers the segfault without the code change.
      
     @@ dir.c: static void add_pattern_to_hashsets(struct pattern_list *pl, struct path_
      -		hashmap_remove(&pl->parent_hashmap, &translated->ent, &data);
      -		free(data);
      -		free(translated);
     ++		goto clear_hashmaps;
       	}
       
       	return;
     @@ t/t1091-sparse-checkout-builtin.sh: test_expect_success 'cone mode clears ignore
      +	!/foo/*/
      +	/foo/\*/
      +	EOF
     -+	cat repo/.git/info/sparse-checkout &&
     -+	git -C repo sparse-checkout list
     ++
     ++	# Listing the patterns will notice the duplicate pattern and
     ++	# emit a warning. It will list the patterns directly instead
     ++	# of using the cone-mode translation to a set of directories.
     ++	git -C repo sparse-checkout list >actual 2>err &&
     ++	test_cmp repo/.git/info/sparse-checkout actual &&
     ++	grep "warning: your sparse-checkout file may have issues: pattern .* is repeated" err &&
     ++	grep "warning: disabling cone pattern matching" err
      +'
      +
       test_done
 2:  a2fe867222e = 2:  3fd625290a3 sparse-checkout: fix OOM error with mixed patterns
 3:  a0e5a942ae0 = 3:  f5f7b8b8e04 sparse-checkout: refuse to add to bad patterns