# [PATCH] sequencer: fix memory leak if `todo_list_rearrange_squash()` failed 4 messages from 2025-05-14 to 2025-05-15. Participants: Lidong Yan via GitGitGadget, Phillip Wood, lidongyan, Junio C Hamano. Thread: https://gitlist.dev/t/63457 ## Lidong Yan via GitGitGadget, 2025-05-14 13:53 Subject: [PATCH] sequencer: fix memory leak if `todo_list_rearrange_squash()` failed Message-ID: URL: https://gitlist.dev/e/pull.1965.git.git.1747230808770.gitgitgadget%40gmail.com ``` From: Lidong Yan <502024330056@smail.nju.edu.cn> In sequencer.c:todo_list_rearrange_squash, if it fails, memory allocated in `next`, `tail`, `subjects` and `subject2item` will leak. Jump to cleanup label before return could fix this leak problem. Signed-off-by: Lidong Yan <502024330056@smail.nju.edu.cn> --- sequencer: fix memory leak if todo_list_rearrange_squash() failed In sequencer.c:todo_list_rearrange_squash, if it fails, memory allocated in next, tail, subjects and subject2item will leak. Jump to cleanup label before return could fix this leak problem. Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-1965%2Fbrandb97%2Ffix-sequencer-todo-leak-v1 Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-1965/brandb97/fix-sequencer-todo-leak-v1 Pull-Request: https://github.com/git/git/pull/1965 sequencer.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/sequencer.c b/sequencer.c index b5c4043757e..5fb7b68a7ab 100644 --- a/sequencer.c +++ b/sequencer.c @@ -6596,6 +6596,7 @@ int todo_list_rearrange_squash(struct todo_list *todo_list) char **subjects; struct commit_todo_item commit_todo; struct todo_item *items = NULL; + int ret = 0; init_commit_todo_item(&commit_todo); /* @@ -6626,8 +6627,8 @@ int todo_list_rearrange_squash(struct todo_list *todo_list) } if (is_fixup(item->command)) { - clear_commit_todo_item(&commit_todo); - return error(_("the script was already rearranged.")); + ret = error(_("the script was already rearranged.")); + goto cleanup; } repo_parse_commit(the_repository, item->commit); @@ -6729,6 +6730,7 @@ int todo_list_rearrange_squash(struct todo_list *todo_list) todo_list->items = items; } +cleanup: free(next); free(tail); for (i = 0; i < todo_list->nr; i++) @@ -6738,7 +6740,7 @@ int todo_list_rearrange_squash(struct todo_list *todo_list) clear_commit_todo_item(&commit_todo); - return 0; + return ret; } int sequencer_determine_whence(struct repository *r, enum commit_whence *whence) base-commit: 6f84262c44a89851c3ae5a6e4c1a9d06b2068d75 -- gitgitgadget ``` ## Phillip Wood, 2025-05-15 10:08 Subject: Re: [PATCH] sequencer: fix memory leak if `todo_list_rearrange_squash()` failed Message-ID: <52e0a717-f7f0-401d-b621-f1f6e028e595@gmail.com> URL: https://gitlist.dev/e/52e0a717-f7f0-401d-b621-f1f6e028e595%40gmail.com In-Reply-To: ``` On 14/05/2025 14:53, Lidong Yan via GitGitGadget wrote: > From: Lidong Yan <502024330056@smail.nju.edu.cn> > > In sequencer.c:todo_list_rearrange_squash, if it fails, memory > allocated in `next`, `tail`, `subjects` and `subject2item` will leak. > Jump to cleanup label before return could fix this leak problem. You could mention that you're adding the cleanup label. I suspect reaching this condition is a bug as well because we should only rearrange the todo list when the rebase starts. However I'm not 100% sure that it is impossible to trigger this condition so lets free it as you suggest. The code changes look good. Out of interest how are you finding these leaks? Thanks Phillip > Signed-off-by: Lidong Yan <502024330056@smail.nju.edu.cn> > --- > sequencer: fix memory leak if todo_list_rearrange_squash() failed > > In sequencer.c:todo_list_rearrange_squash, if it fails, memory allocated > in next, tail, subjects and subject2item will leak. Jump to cleanup > label before return could fix this leak problem. > > Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-1965%2Fbrandb97%2Ffix-sequencer-todo-leak-v1 > Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-1965/brandb97/fix-sequencer-todo-leak-v1 > Pull-Request: https://github.com/git/git/pull/1965 > > sequencer.c | 8 +++++--- > 1 file changed, 5 insertions(+), 3 deletions(-) > > diff --git a/sequencer.c b/sequencer.c > index b5c4043757e..5fb7b68a7ab 100644 > --- a/sequencer.c > +++ b/sequencer.c > @@ -6596,6 +6596,7 @@ int todo_list_rearrange_squash(struct todo_list *todo_list) > char **subjects; > struct commit_todo_item commit_todo; > struct todo_item *items = NULL; > + int ret = 0; > > init_commit_todo_item(&commit_todo); > /* > @@ -6626,8 +6627,8 @@ int todo_list_rearrange_squash(struct todo_list *todo_list) > } > > if (is_fixup(item->command)) { > - clear_commit_todo_item(&commit_todo); > - return error(_("the script was already rearranged.")); > + ret = error(_("the script was already rearranged.")); > + goto cleanup; > } > > repo_parse_commit(the_repository, item->commit); > @@ -6729,6 +6730,7 @@ int todo_list_rearrange_squash(struct todo_list *todo_list) > todo_list->items = items; > } > > +cleanup: > free(next); > free(tail); > for (i = 0; i < todo_list->nr; i++) > @@ -6738,7 +6740,7 @@ int todo_list_rearrange_squash(struct todo_list *todo_list) > > clear_commit_todo_item(&commit_todo); > > - return 0; > + return ret; > } > > int sequencer_determine_whence(struct repository *r, enum commit_whence *whence) > > base-commit: 6f84262c44a89851c3ae5a6e4c1a9d06b2068d75 ``` ## lidongyan, 2025-05-15 10:45 Subject: Re: [PATCH] sequencer: fix memory leak if `todo_list_rearrange_squash()` failed Message-ID: URL: https://gitlist.dev/e/EEC15708-1EBA-45B7-BC79-980858634AE0%40smail.nju.edu.cn In-Reply-To: <52e0a717-f7f0-401d-b621-f1f6e028e595@gmail.com> ``` 2025/5/15 18:08，Phillip Wood 写道： > > On 14/05/2025 14:53, Lidong Yan via GitGitGadget wrote: >> From: Lidong Yan <502024330056@smail.nju.edu.cn> >> In sequencer.c:todo_list_rearrange_squash, if it fails, memory >> allocated in `next`, `tail`, `subjects` and `subject2item` will leak. >> Jump to cleanup label before return could fix this leak problem. > > You could mention that you're adding the cleanup label. Understood. I will pay attention to this in future patches. > Out of interest how are you finding these leaks? I am a graduate student at Nanjing University, working in collaboration with Professor [Qingkai Shi](https://qingkaishi.github.io/). We are currently developing a tool for statically analyzing memory leaks in C programs, and I am testing this tool on Git. To ensure the validity of our testing results, we are submitting patches to Git and seeking confirmation from you developers. ``` ## Junio C Hamano, 2025-05-15 16:37 Subject: Re: [PATCH] sequencer: fix memory leak if `todo_list_rearrange_squash()` failed Message-ID: URL: https://gitlist.dev/e/xmqqecwp3k5h.fsf%40gitster.g In-Reply-To: <52e0a717-f7f0-401d-b621-f1f6e028e595@gmail.com> ``` Phillip Wood writes: > On 14/05/2025 14:53, Lidong Yan via GitGitGadget wrote: >> From: Lidong Yan <502024330056@smail.nju.edu.cn> >> In sequencer.c:todo_list_rearrange_squash, if it fails, memory >> allocated in `next`, `tail`, `subjects` and `subject2item` will leak. >> Jump to cleanup label before return could fix this leak problem. > > You could mention that you're adding the cleanup label. > > I suspect reaching this condition is a bug as well because we should > only rearrange the todo list when the rebase starts. However I'm not > 100% sure that it is impossible to trigger this condition so lets free > it as you suggest. The code changes look good. I wonder if there is a way (sort of using BUG("") but not as severe as killing the program) for us to mark "we do not expect this code path to be taken" and ask static analysis or fuzzers to disprove such assertions. The message being an error(), without a silent return doing nothing, smells like a good enough sign, at least to me, that the original author intended not to call this helper function on a list that was already rearranged, so turning this into BUG("") may be something we would want to consider doing in the longer term. >> @@ -6626,8 +6627,8 @@ int todo_list_rearrange_squash(struct todo_list *todo_list) >> } >> if (is_fixup(item->command)) { >> - clear_commit_todo_item(&commit_todo); >> - return error(_("the script was already rearranged.")); >> + ret = error(_("the script was already rearranged.")); >> + goto cleanup; >> } Thanks. ```