libgit2: Patch race condition with fake repositories

1 files changed, 146 insertions, 0 deletions

diff --git a/etc/patches/libgit2_v1.1.0_fix-fake-repo.patch b/etc/patches/libgit2_v1.1.0_fix-fake-repo.patch
new file mode 100644
index 00000000..85bab5a6
--- /dev/null
+++ b/etc/patches/libgit2_v1.1.0_fix-fake-repo.patch
@@ -0,0 +1,146 @@
+From bf27a288adce36e2a57e26146d18c224ebc745be Mon Sep 17 00:00:00 2001
+From: Oliver Reiche <oliver.reiche@huawei.com>
+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 513dbd61f..9e5aa6a16 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;
+@@ -722,7 +724,7 @@ 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) {
+@@ -932,7 +934,7 @@ 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;
+@@ -1139,10 +1141,10 @@ 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)
+ {
+ 	assert(repo && 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..bf1b31783 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"));
++	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);
+-- 
+2.25.1
+