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init: remove git_init_db_config() while fixing leaks

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The primary goal of this change is to stop leaking init_db_template_dir.
This leak can happen because:
 1. git_init_db_config() allocates new memory into init_db_template_dir
    without first freeing the existing value.
 2. init_db_template_dir might already contain data, either because:
  2.1 git_config() can be invoked twice with this callback in a single
      process - at least 2 allocations are likely.
  2.2 A single git_config() allocation can invoke the callback multiple
      times for a given key (see further explanation in the function
      docs) - each of those calls will trigger another leak.

The simplest fix for the leak would be to free(init_db_template_dir)
before overwriting it. Instead we choose to convert to fetching
init.templatedir via git_config_get_value() as that is more explicit,
more efficient, and avoids allocations (the returned result is owned by
the config cache, so we aren't responsible for freeing it).

If we remove init_db_template_dir, git_init_db_config() ends up being
responsible only for forwarding core.* config values to
platform_core_config(). However platform_core_config() already ignores
non-core.* config values, so we can safely remove git_init_db_config()
and invoke git_config() directly with platform_core_config() as the
callback.

The platform_core_config forwarding was originally added in:
  287853392a (mingw: respect core.hidedotfiles = false in git-init again, 2019-03-11
And I suspect the potential for a leak existed since the original
implementation of git_init_db_config in:
  90b45187ba (Add `init.templatedir` configuration variable., 2010-02-17)

LSAN output from t0001:

Direct leak of 73 byte(s) in 1 object(s) allocated from:
    #0 0x49a859 in realloc /home/abuild/rpmbuild/BUILD/llvm-11.0.0.src/build/../projects/compiler-rt/lib/asan/asan_malloc_linux.cpp:164:3
    #1 0x9a7276 in xrealloc /home/ahunt/oss-fuzz/git/wrapper.c:126:8
    #2 0x9362ad in strbuf_grow /home/ahunt/oss-fuzz/git/strbuf.c:98:2
    #3 0x936eaa in strbuf_add /home/ahunt/oss-fuzz/git/strbuf.c:295:2
    #4 0x868112 in strbuf_addstr /home/ahunt/oss-fuzz/git/./strbuf.h:304:2
    #5 0x86a8ad in expand_user_path /home/ahunt/oss-fuzz/git/path.c:758:2
    #6 0x720bb1 in git_config_pathname /home/ahunt/oss-fuzz/git/config.c:1287:10
    #7 0x5960e2 in git_init_db_config /home/ahunt/oss-fuzz/git/builtin/init-db.c:161:11
    #8 0x7255b8 in configset_iter /home/ahunt/oss-fuzz/git/config.c:1982:7
    #9 0x7253fc in repo_config /home/ahunt/oss-fuzz/git/config.c:2311:2
    #10 0x725ca7 in git_config /home/ahunt/oss-fuzz/git/config.c:2399:2
    #11 0x593e8d in create_default_files /home/ahunt/oss-fuzz/git/builtin/init-db.c:225:2
    #12 0x5935c6 in init_db /home/ahunt/oss-fuzz/git/builtin/init-db.c:449:11
    #13 0x59588e in cmd_init_db /home/ahunt/oss-fuzz/git/builtin/init-db.c:714:9
    #14 0x4cd60d in run_builtin /home/ahunt/oss-fuzz/git/git.c:453:11
    #15 0x4cb2da in handle_builtin /home/ahunt/oss-fuzz/git/git.c:704:3
    #16 0x4ccc37 in run_argv /home/ahunt/oss-fuzz/git/git.c:771:4
    #17 0x4cac29 in cmd_main /home/ahunt/oss-fuzz/git/git.c:902:19
    #18 0x69c4de in main /home/ahunt/oss-fuzz/git/common-main.c:52:11
    #19 0x7f23552d6349 in __libc_start_main (/lib64/libc.so.6+0x24349)

Signed-off-by: Andrzej Hunt <ajrhunt@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Andrzej Hunt 2021-03-14 18:47:38 +00:00 committed by Junio C Hamano
parent aa1b63971a
commit e4de4502e6
1 changed files with 7 additions and 21 deletions
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28
builtin/init-db.c
View File

@ -25,7 +25,6 @@
static int init_is_bare_repository = 0;
static int init_shared_repository = -1;
static const char *init_db_template_dir;
static void copy_templates_1(struct strbuf *path, struct strbuf *template_path,
DIR *dir)
@ -94,7 +93,7 @@ static void copy_templates_1(struct strbuf *path, struct strbuf *template_path,
}
}
static void copy_templates(const char *template_dir)
static void copy_templates(const char *template_dir, const char *init_template_dir)
{
struct strbuf path = STRBUF_INIT;
struct strbuf template_path = STRBUF_INIT;
@ -107,7 +106,7 @@ static void copy_templates(const char *template_dir)
if (!template_dir)
template_dir = getenv(TEMPLATE_DIR_ENVIRONMENT);
if (!template_dir)
template_dir = init_db_template_dir;
template_dir = init_template_dir;
if (!template_dir)
template_dir = to_free = system_path(DEFAULT_GIT_TEMPLATE_DIR);
if (!template_dir[0]) {
@ -154,17 +153,6 @@ free_return:
clear_repository_format(&template_format);
}
static int git_init_db_config(const char *k, const char *v, void *cb)
{
if (!strcmp(k, "init.templatedir"))
return git_config_pathname(&init_db_template_dir, k, v);
if (starts_with(k, "core."))
return platform_core_config(k, v, cb);
return 0;
}
/*
* If the git_dir is not directly inside the working tree, then git will not
* find it by default, and we need to set the worktree explicitly.
@ -212,10 +200,7 @@ static int create_default_files(const char *template_path,
int reinit;
int filemode;
struct strbuf err = STRBUF_INIT;
/* Just look for `init.templatedir` */
init_db_template_dir = NULL; /* re-set in case it was set before */
git_config(git_init_db_config, NULL);
const char *init_template_dir = NULL;
/*
* First copy the templates -- we might have the default
@ -226,7 +211,8 @@ static int create_default_files(const char *template_path,
* values (since we've just potentially changed what's available on
* disk).
*/
copy_templates(template_path);
git_config_get_value("init.templatedir", &init_template_dir);
copy_templates(template_path, init_template_dir);
git_config_clear();
reset_shared_repository();
git_config(git_default_config, NULL);
@ -422,8 +408,8 @@ int init_db(const char *git_dir, const char *real_git_dir,
}
startup_info->have_repository = 1;
/* Just look for `core.hidedotfiles` */
git_config(git_init_db_config, NULL);
/* Ensure `core.hidedotfiles` is processed */
git_config(platform_core_config, NULL);
safe_create_dir(git_dir, 0);