Hi Jinoh,
On Tue, 10 Nov 2020, Jinoh Kang wrote:
> Today, diff_free_filespec_data crashes when passed a NULL pointer.
> Commit 3aef54e8b8 ("diff: munmap() file contents before running external
> diff") introduced calls to diff_free_filespec_data in run_external_diff,
> which may pass NULL pointers.
>
> Git uses NULL filespecs to indicate unmerged files when merge conflict
> resolution is in progress. Fortunately, other code paths bail out early
> even before NULL can reach diff_free_filespec_data(); however, difftool
> is expected to do a full-blown diff anyway regardless of conflict
> status.
>
> Fix this and prevent any similar bugs in the future by making
> `diff_free_filespec_data(NULL)` a no-op.
>
> Also, add a test case that confirms that running difftool --cached with
> unmerged files does not SIGSEGV.
>
> Signed-off-by: Jinoh Kang <luke1337@xxxxxxxxx>
> ---
> diff.c | 3 +++
> t/t7800-difftool.sh | 23 +++++++++++++++++++++++
> 2 files changed, 26 insertions(+)
>
> diff --git a/diff.c b/diff.c
> index d24f47df99..ace4a1d387 100644
> --- a/diff.c
> +++ b/diff.c
> @@ -4115,6 +4115,9 @@ void diff_free_filespec_blob(struct diff_filespec *s)
>
> void diff_free_filespec_data(struct diff_filespec *s)
> {
> + if (!s)
> + return;
> +
I had suggested an improvement for this hunk as well as for the test case.
Fell through the cracks?
Ciao,
Dscho
> diff_free_filespec_blob(s);
> FREE_AND_NULL(s->cnt_data);
> }
> diff --git a/t/t7800-difftool.sh b/t/t7800-difftool.sh
> index 524f30f7dc..e9391abb54 100755
> --- a/t/t7800-difftool.sh
> +++ b/t/t7800-difftool.sh
> @@ -728,6 +728,29 @@ test_expect_success 'add -N and difftool -d' '
> git difftool --dir-diff --extcmd ls
> '
>
> +test_expect_success 'difftool --cached with unmerged files' '
> + test_when_finished git reset --hard &&
> + echo base >file &&
> + git add file &&
> + git commit -m base &&
> + git checkout -B conflict-a &&
> + git checkout -B conflict-b &&
> + git checkout conflict-a &&
> + echo conflict-a >>file &&
> + git add file &&
> + git commit -m conflict-a &&
> + git checkout conflict-b &&
> + echo conflict-b >>file &&
> + git add file &&
> + git commit -m conflict-b &&
> + git checkout master &&
> + git merge conflict-a &&
> + test_must_fail git merge conflict-b &&
> + : >expect &&
> + git difftool --cached --no-prompt >actual &&
> + test_cmp expect actual
> +'
> +
> test_expect_success 'outside worktree' '
> echo 1 >1 &&
> echo 2 >2 &&
> --
> 2.26.2
>
