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[v2,1/3] unpack-trees: don't leak memory in verify_clean_subdirectory()

Message ID patch-v2-1.3-e5ef1be2aa9-20211007T094019Z-avarab@gmail.com (mailing list archive)
State Superseded
Headers show
Series unpack-trees: memory-leak fixes | expand

Commit Message

Ævar Arnfjörð Bjarmason Oct. 7, 2021, 9:46 a.m. UTC
Fix two different but related memory leaks in
verify_clean_subdirectory(). We leaked both the "pathbuf" if
read_directory() returned non-zero, and we never cleaned up our own
"struct dir_struct" either.

 * "pathbuf": When the read_directory() call followed by the
   free(pathbuf) was added in c81935348be (Fix switching to a branch
   with D/F when current branch has file D., 2007-03-15) we didn't
   bother to free() before we called die().

   But when this code was later libified in 203a2fe1170 (Allow callers
   of unpack_trees() to handle failure, 2008-02-07) we started to leak
   as we returned data to the caller. This fixes that memory leak,
   which can be observed under SANITIZE=leak with e.g. the
   "t1001-read-tree-m-2way.sh" test.

 * "struct dir_struct": We've leaked the dir_struct ever since this
   code was added back in c81935348be.

   When that commit was written there wasn't an equivalent of
   dir_clear(). Since it was added in 270be816049 (dir.c: provide
   clear_directory() for reclaiming dir_struct memory, 2013-01-06)
   we've omitted freeing the memory allocated here.

   This memory leak could also be observed under SANITIZE=leak and the
   "t1001-read-tree-m-2way.sh" test.

This makes all the test in "t1001-read-tree-m-2way.sh" pass under
"GIT_TEST_PASSING_SANITIZE_LEAK=true", we'd previously die in tests
25, 26 & 28.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
---
 t/t1001-read-tree-m-2way.sh | 2 ++
 unpack-trees.c              | 3 ++-
 2 files changed, 4 insertions(+), 1 deletion(-)

Comments

Junio C Hamano Oct. 7, 2021, 10:27 p.m. UTC | #1
Ævar Arnfjörð Bjarmason  <avarab@gmail.com> writes:

> diff --git a/unpack-trees.c b/unpack-trees.c
> index a7e1712d236..89ca95ce90b 100644
> --- a/unpack-trees.c
> +++ b/unpack-trees.c
> @@ -2156,9 +2156,10 @@ static int verify_clean_subdirectory(const struct cache_entry *ce,
>  	if (o->dir)
>  		d.exclude_per_dir = o->dir->exclude_per_dir;
>  	i = read_directory(&d, o->src_index, pathbuf, namelen+1, NULL);
> +	dir_clear(&d);
> +	free(pathbuf);
>  	if (i)
>  		return add_rejected_path(o, ERROR_NOT_UPTODATE_DIR, ce->name);
> -	free(pathbuf);
>  	return cnt;
>  }

Looks trivially correct.
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Patch

diff --git a/t/t1001-read-tree-m-2way.sh b/t/t1001-read-tree-m-2way.sh
index 1057a96b249..d1115528cb9 100755
--- a/t/t1001-read-tree-m-2way.sh
+++ b/t/t1001-read-tree-m-2way.sh
@@ -20,6 +20,8 @@  In the test, these paths are used:
 	rezrov  - in H, deleted in M
 	yomin   - not in H or M
 '
+
+TEST_PASSES_SANITIZE_LEAK=true
 . ./test-lib.sh
 . "$TEST_DIRECTORY"/lib-read-tree.sh
 
diff --git a/unpack-trees.c b/unpack-trees.c
index a7e1712d236..89ca95ce90b 100644
--- a/unpack-trees.c
+++ b/unpack-trees.c
@@ -2156,9 +2156,10 @@  static int verify_clean_subdirectory(const struct cache_entry *ce,
 	if (o->dir)
 		d.exclude_per_dir = o->dir->exclude_per_dir;
 	i = read_directory(&d, o->src_index, pathbuf, namelen+1, NULL);
+	dir_clear(&d);
+	free(pathbuf);
 	if (i)
 		return add_rejected_path(o, ERROR_NOT_UPTODATE_DIR, ce->name);
-	free(pathbuf);
 	return cnt;
 }