@matheusbsbs / matheus-bagliano / commits / 351c6e719a

refs/ref-cache: fix SEGFAULT when seeking in empty directories

The 'cache_ref_iterator_seek()' function is used to seek the `ref_iterator` to the desired reference in the ref-cache mechanism. We use the seeking functionality to implement the '--start-after' flag in 'git-for-each-ref(1)'. When using the files-backend with packed-refs, it is possible that some of the refs directories are empty. For e.g. just after repacking, the 'refs/heads' directory would be empty. The ref-cache seek mechanism, doesn't take this into consideration when descending into a subdirectory, and makes an out of bounds access, causing SEGFAULT as we try to access entries within the directory. Fix this by breaking out of the loop when we enter an empty directory. Since we start with the base directory of 'refs/' which is never empty, it is okay to perform this check after the first iteration in the `do..while` clause. Add tests which simulate this behavior and also provide coverage over using the feature over packed-refs. Helped-by: Junio C Hamano <gitster@pobox.com> Signed-off-by: Karthik Nayak <karthik.188@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>

Karthik Nayak committed Oct 1, 2025 at 14:17 UTC 351c6e719ae9c5b97506dde6bc287408b80e87e4
2 files changed +66 -1
refs/ref-cache.c
+1 -1
@@ -539,7 +539,7 @@ static int cache_ref_iterator_seek(struct ref_iterator *ref_iterator,
539 */
540 break;
541 }
542 - } while (slash);
542 + } while (slash && dir->nr);
543 }
544
545 return 0;
t/t6302-for-each-ref-filter.sh
+65
@@ -754,4 +754,69 @@ test_expect_success 'start after used with custom sort order' '
754 test_cmp expect actual
755 '
756
757 +test_expect_success 'start after with packed refs' '
758 + test_when_finished "rm -rf repo" &&
759 + git init repo &&
760 + (
761 + cd repo &&
762 + test_commit default &&
763 +
764 + git update-ref --stdin <<-\EOF &&
765 + create refs/heads/branch @
766 + create refs/heads/side @
767 + create refs/odd/spot @
768 + create refs/tags/one @
769 + create refs/tags/two @
770 + commit
771 + EOF
772 +
773 + cat >expect <<-\EOF &&
774 + refs/tags/default
775 + refs/tags/one
776 + refs/tags/two
777 + EOF
778 +
779 + git pack-refs --all &&
780 + git for-each-ref --format="%(refname)" --start-after=refs/odd/spot >actual &&
781 + test_cmp expect actual
782 + )
783 +'
784 +
785 +test_expect_success 'start after with packed refs and some loose refs' '
786 + test_when_finished "rm -rf repo" &&
787 + git init repo &&
788 + (
789 + cd repo &&
790 + test_commit default &&
791 +
792 + git update-ref --stdin <<-\EOF &&
793 + create refs/heads/branch @
794 + create refs/heads/side @
795 + create refs/odd/spot @
796 + create refs/tags/one @
797 + create refs/tags/two @
798 + commit
799 + EOF
800 +
801 + git pack-refs --all &&
802 +
803 + git update-ref --stdin <<-\EOF &&
804 + create refs/heads/foo @
805 + create refs/odd/tee @
806 + commit
807 + EOF
808 +
809 + cat >expect <<-\EOF &&
810 + refs/odd/tee
811 + refs/tags/default
812 + refs/tags/one
813 + refs/tags/two
814 + EOF
815 +
816 +
817 + git for-each-ref --format="%(refname)" --start-after=refs/odd/spot >actual &&
818 + test_cmp expect actual
819 + )
820 +'
821 +
822 test_done