From 6eb095d78790d0d6cbad2186685dad4e7ba2e3de Mon Sep 17 00:00:00 2001 From: Patrick Steinhardt Date: Thu, 16 Feb 2023 11:29:48 +0100 Subject: [PATCH] delta-islands: fix segfault when freeing island marks In 647982bb71 (delta-islands: free island_marks and bitmaps, 2023-02-03) we have introduced logic to free `island_marks` in order to reduce heap memory usage in git-pack-objects(1). This commit is causing segfaults in the case where this Git command does not load delta islands at all, e.g. when reading object IDs from standard input. One such crash can be hit when using repacking multi-pack-indices with delta islands enabled. The root cause of this bug is that we unconditionally dereference the `island_marks` variable even in the case where it is a `NULL` pointer, which is fixed by making it conditional. Note that we still leave the logic in place to set the pointer to `-1` to detect use-after-free bugs even when there are no loaded island marks at all. Signed-off-by: Patrick Steinhardt Acked-by: Eric Wong Signed-off-by: Junio C Hamano --- delta-islands.c | 12 +++++++----- t/t5319-multi-pack-index.sh | 16 ++++++++++++++++ 2 files changed, 23 insertions(+), 5 deletions(-) diff --git a/delta-islands.c b/delta-islands.c index 8b234cb85b..afdec0a878 100644 --- a/delta-islands.c +++ b/delta-islands.c @@ -517,11 +517,13 @@ void free_island_marks(void) { struct island_bitmap *bitmap; - kh_foreach_value(island_marks, bitmap, { - if (!--bitmap->refcount) - free(bitmap); - }); - kh_destroy_oid_map(island_marks); + if (island_marks) { + kh_foreach_value(island_marks, bitmap, { + if (!--bitmap->refcount) + free(bitmap); + }); + kh_destroy_oid_map(island_marks); + } /* detect use-after-free with a an address which is never valid: */ island_marks = (void *)-1; diff --git a/t/t5319-multi-pack-index.sh b/t/t5319-multi-pack-index.sh index b5f9b10922..499d5d4c78 100755 --- a/t/t5319-multi-pack-index.sh +++ b/t/t5319-multi-pack-index.sh @@ -1015,4 +1015,20 @@ test_expect_success 'complains when run outside of a repository' ' grep "not a git repository" err ' +test_expect_success 'repack with delta islands' ' + git init repo && + test_when_finished "rm -fr repo" && + ( + cd repo && + + test_commit first && + git repack && + test_commit second && + git repack && + + git multi-pack-index write && + git -c repack.useDeltaIslands=true multi-pack-index repack + ) +' + test_done