From: Simon Marchi <simon.marchi@xxxxxxxxxxxx>
When running a dir-diff command that produces no diff, variables
`wt_modified` and `tmp_modified` are used while uninitialized, causing:
$ /home/smarchi/src/git/git-difftool --dir-diff master
free(): invalid pointer
[1] 334004 IOT instruction (core dumped) /home/smarchi/src/git/git-difftool --dir-diff master
$ valgrind --track-origins=yes /home/smarchi/src/git/git-difftool --dir-diff master
...
Invalid free() / delete / delete[] / realloc()
at 0x48478EF: free (vg_replace_malloc.c:989)
by 0x422CAC: hashmap_clear_ (hashmap.c:208)
by 0x283830: run_dir_diff (difftool.c:667)
by 0x284103: cmd_difftool (difftool.c:801)
by 0x238E0F: run_builtin (git.c:484)
by 0x2392B9: handle_builtin (git.c:750)
by 0x2399BC: cmd_main (git.c:921)
by 0x356FEF: main (common-main.c:64)
Address 0x1ffefff180 is on thread 1's stack
in frame #2, created by run_dir_diff (difftool.c:358)
...
If taking any `goto finish` path before these variables are initialized,
`hashmap_clear_and_free()` operates on uninitialized data, sometimes
causing a crash.
This regression was introduced in 7f795a1715 (builtin/difftool: plug
several trivial memory leaks, 2024-09-26).
Fix it by initializing those variables with the `HASHMAP_INIT` macro.
Add a test comparing the main branch to itself, resulting in no diff.
Signed-off-by: Simon Marchi <simon.marchi@xxxxxxxxxxxx>
Cc: Junio C Hamano <gitster@xxxxxxxxx>
Cc: René Scharfe <l.s.r@xxxxxx>
Cc: Taylor Blau <me@xxxxxxxxxxxx>
Cc: Patrick Steinhardt <ps@xxxxxx>
---
New in v2:
- Use the `HASHMAP_INIT` macro instead of zero-initializing the
variables.
- Improve an existing test to cover this case.
---
builtin/difftool.c | 6 ++----
t/t7800-difftool.sh | 4 ++++
2 files changed, 6 insertions(+), 4 deletions(-)
diff --git a/builtin/difftool.c b/builtin/difftool.c
index ca1b0890659b..40e971e2259d 100644
--- a/builtin/difftool.c
+++ b/builtin/difftool.c
@@ -376,7 +376,8 @@ static int run_dir_diff(const char *extcmd, int symlinks, const char *prefix,
struct checkout lstate, rstate;
int err = 0;
struct child_process cmd = CHILD_PROCESS_INIT;
- struct hashmap wt_modified, tmp_modified;
+ struct hashmap wt_modified = HASHMAP_INIT(path_entry_cmp, NULL);
+ struct hashmap tmp_modified = HASHMAP_INIT(path_entry_cmp, NULL);
int indices_loaded = 0;
workdir = repo_get_work_tree(the_repository);
@@ -601,9 +602,6 @@ static int run_dir_diff(const char *extcmd, int symlinks, const char *prefix,
* in the common case of --symlinks and the difftool updating
* files through the symlink.
*/
- hashmap_init(&wt_modified, path_entry_cmp, NULL, wtindex.cache_nr);
- hashmap_init(&tmp_modified, path_entry_cmp, NULL, wtindex.cache_nr);
-
for (i = 0; i < wtindex.cache_nr; i++) {
struct hashmap_entry dummy;
const char *name = wtindex.cache[i]->name;
diff --git a/t/t7800-difftool.sh b/t/t7800-difftool.sh
index f67b9345b8a0..fcaa1748e4a8 100755
--- a/t/t7800-difftool.sh
+++ b/t/t7800-difftool.sh
@@ -666,6 +666,10 @@ run_dir_diff_test 'difftool --dir-diff syncs worktree without unstaged change' '
test_cmp expect file
'
+run_dir_diff_test 'difftool --dir-diff with no diff' '
+ git difftool -d main main
+'
+
write_script modify-file <<\EOF
echo "new content" >file
EOF
base-commit: b31fb630c0fc6869a33ed717163e8a1210460d94
--
2.47.0
