From 1a4497d0aa05b48c40d939713a48bdf78dfa29e9 Mon Sep 17 00:00:00 2001 From: Oliver Reiche Date: Wed, 3 Aug 2022 16:27:58 +0200 Subject: [PATCH] Do not register fake repository as owner of ODB Accessing ODB is guaranteed to be thread-safe. Registering a fake repository (created via git_repository_wrap_odb()) may not register itself as owner of the ODB in order to maintain that guarantee. Otherwise, accessing objects from ODB will try to obtain the cache from the owning repository (via odb_cache()) and produce a race if this ODB is concurrently used to create fake repositories in other threads. Consequently, operations on fake repositories will interact with the ODB's cache instead of the repository's cache. --- include/git2/sys/repository.h | 3 ++- src/repository.c | 16 +++++++++------- tests/odb/backend/nobackend.c | 2 +- tests/repo/setters.c | 23 ++++++++++++++++++++++- 4 files changed, 34 insertions(+), 10 deletions(-) diff --git a/include/git2/sys/repository.h b/include/git2/sys/repository.h index 892be6692..33bc5051f 100644 --- a/include/git2/sys/repository.h +++ b/include/git2/sys/repository.h @@ -97,9 +97,10 @@ GIT_EXTERN(int) git_repository_set_config(git_repository *repo, git_config *conf * * @param repo A repository object * @param odb An ODB object + * @param set_owner Register repository as owner of ODB * @return 0 on success, or an error code */ -GIT_EXTERN(int) git_repository_set_odb(git_repository *repo, git_odb *odb); +GIT_EXTERN(int) git_repository_set_odb(git_repository *repo, git_odb *odb, bool set_owner); /** * Set the Reference Database Backend for this repository diff --git a/src/repository.c b/src/repository.c index aae0c910b..13e1ca29e 100644 --- a/src/repository.c +++ b/src/repository.c @@ -86,10 +86,12 @@ git_buf git_repository__reserved_names_posix[] = { }; size_t git_repository__reserved_names_posix_len = 1; -static void set_odb(git_repository *repo, git_odb *odb) +static void set_odb(git_repository *repo, git_odb *odb, bool set_owner) { if (odb) { - GIT_REFCOUNT_OWN(odb, repo); + if (set_owner) { + GIT_REFCOUNT_OWN(odb, repo); + } GIT_REFCOUNT_INC(odb); } @@ -150,7 +152,7 @@ int git_repository__cleanup(git_repository *repo) set_config(repo, NULL); set_index(repo, NULL); - set_odb(repo, NULL); + set_odb(repo, NULL, /*set_owner=*/true); set_refdb(repo, NULL); return 0; @@ -762,7 +764,7 @@ static int _git_repository_open_ext_from_env( goto error; if (odb) - git_repository_set_odb(repo, odb); + git_repository_set_odb(repo, odb, /*set_owner=*/true); error = git__getenv(&alts_buf, "GIT_ALTERNATE_OBJECT_DIRECTORIES"); if (error == GIT_ENOTFOUND) { @@ -973,7 +975,7 @@ int git_repository_wrap_odb(git_repository **repo_out, git_odb *odb) repo = repository_alloc(); GIT_ERROR_CHECK_ALLOC(repo); - git_repository_set_odb(repo, odb); + git_repository_set_odb(repo, odb, /*set_owner=*/false); *repo_out = repo; return 0; @@ -1184,12 +1186,12 @@ int git_repository_odb(git_odb **out, git_repository *repo) return 0; } -int git_repository_set_odb(git_repository *repo, git_odb *odb) +int git_repository_set_odb(git_repository *repo, git_odb *odb, bool set_owner) { GIT_ASSERT_ARG(repo); GIT_ASSERT_ARG(odb); - set_odb(repo, odb); + set_odb(repo, odb, set_owner); return 0; } diff --git a/tests/odb/backend/nobackend.c b/tests/odb/backend/nobackend.c index 7484d423b..d46a7fed9 100644 --- a/tests/odb/backend/nobackend.c +++ b/tests/odb/backend/nobackend.c @@ -16,7 +16,7 @@ void test_odb_backend_nobackend__initialize(void) cl_git_pass(git_refdb_new(&refdb, _repo)); git_repository_set_config(_repo, config); - git_repository_set_odb(_repo, odb); + git_repository_set_odb(_repo, odb, /*set_owner=*/true); git_repository_set_refdb(_repo, refdb); /* The set increases the refcount and we don't want them anymore */ diff --git a/tests/repo/setters.c b/tests/repo/setters.c index 1fac627f6..e0e0d3696 100644 --- a/tests/repo/setters.c +++ b/tests/repo/setters.c @@ -94,7 +94,28 @@ void test_repo_setters__setting_a_new_odb_on_a_repo_which_already_loaded_one_pro cl_git_pass(git_odb_open(&new_odb, "./testrepo.git/objects")); cl_assert(((git_refcount *)new_odb)->refcount.val == 1); - git_repository_set_odb(repo, new_odb); + git_repository_set_odb(repo, new_odb, /*set_owner=*/true); + cl_assert(((git_refcount *)new_odb)->refcount.val == 2); + + git_repository_free(repo); + cl_assert(((git_refcount *)new_odb)->refcount.val == 1); + + git_odb_free(new_odb); + + /* + * Ensure the cleanup method won't try to free the repo as it's already been taken care of + */ + repo = NULL; +} + +void test_repo_setters__setting_a_new_odb_on_a_non_owner_repo_which_already_loaded_one_properly_honors_the_refcount(void) +{ + git_odb *new_odb; + + cl_git_pass(git_odb__open(&new_odb, "./testrepo.git/objects", NULL)); + cl_assert(((git_refcount *)new_odb)->refcount.val == 1); + + git_repository_set_odb(repo, new_odb, /*set_owner=*/false); cl_assert(((git_refcount *)new_odb)->refcount.val == 2); git_repository_free(repo); -- 2.30.2