diff_free_filespec_data crashes when passed a NULL fillspec pointer.
Commit 3aef54e8b8 ("diff: munmap() file contents before running external
diff", 2019-07-11) introduced calls to diff_free_filespec_data in
run_external_diff without also checking if the argument is NULL.
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.
Add a test case that confirms that running difftool --cached with
unmerged files does not result in a SIGSEGV.
Signed-off-by: Jinoh Kang <luke1337@xxxxxxxxx>
---
diff.c | 3 +++
t/t7800-difftool.sh | 13 +++++++++++++
2 files changed, 16 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;
+
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..a578b35761 100755
--- a/t/t7800-difftool.sh
+++ b/t/t7800-difftool.sh
@@ -728,6 +728,19 @@ 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 &&
+
+ test_commit conflicting &&
+ test_commit conflict-a conflict.t a &&
+ git reset --hard conflicting &&
+ test_commit conflict-b conflict.t b &&
+ test_must_fail git merge conflict-a &&
+
+ git difftool --cached --no-prompt >output &&
+ test_must_be_empty output
+'
+
test_expect_success 'outside worktree' '
echo 1 >1 &&
echo 2 >2 &&
--
2.26.2
