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set_git_dir: fix crash when used with real_path()

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`real_path()` returns result from a shared buffer, inviting subtle
reentrance bugs. One of these bugs occur when invoked this way:
    set_git_dir(real_path(git_dir))

In this case, `real_path()` has reentrance:
    real_path
    read_gitfile_gently
    repo_set_gitdir
    setup_git_env
    set_git_dir_1
    set_git_dir

Later, `set_git_dir()` uses its now-dead parameter:
    !is_absolute_path(path)

Fix this by using a dedicated `strbuf` to hold `strbuf_realpath()`.

Signed-off-by: Alexandr Miloslavskiy <alexandr.miloslavskiy@syntevo.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Alexandr Miloslavskiy 2020-03-06 19:03:13 +00:00 committed by Junio C Hamano
parent 076cbdcd73
commit 0915a5b4cd
5 changed files with 23 additions and 14 deletions
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4
builtin/init-db.c
View file

@ -356,12 +356,12 @@ int init_db(const char *git_dir, const char *real_git_dir,
if (!exist_ok && !stat(real_git_dir, &st))
die(_("%s already exists"), real_git_dir);
set_git_dir(real_path(real_git_dir));
set_git_dir(real_git_dir, 1);
git_dir = get_git_dir();
separate_git_dir(git_dir, original_git_dir);
}
else {
set_git_dir(real_path(git_dir));
set_git_dir(git_dir, 1);
git_dir = get_git_dir();
}
startup_info->have_repository = 1;

2
cache.h
View file

@ -543,7 +543,7 @@ const char *get_git_common_dir(void);
char *get_object_directory(void);
char *get_index_file(void);
char *get_graft_file(struct repository *r);
void set_git_dir(const char *path);
void set_git_dir(const char *path, int make_realpath);
int get_common_dir_noenv(struct strbuf *sb, const char *gitdir);
int get_common_dir(struct strbuf *sb, const char *gitdir);
const char *get_git_namespace(void);

11
environment.c
View file

@ -345,11 +345,20 @@ static void update_relative_gitdir(const char *name,
free(path);
}
void set_git_dir(const char *path)
void set_git_dir(const char *path, int make_realpath)
{
struct strbuf realpath = STRBUF_INIT;
if (make_realpath) {
strbuf_realpath(&realpath, path, 1);
path = realpath.buf;
}
set_git_dir_1(path);
if (!is_absolute_path(path))
chdir_notify_register(NULL, update_relative_gitdir, NULL);
strbuf_release(&realpath);
}
const char *get_log_output_encoding(void)

2
path.c
View file

@ -850,7 +850,7 @@ const char *enter_repo(const char *path, int strict)
}
if (is_git_directory(".")) {
set_git_dir(".");
set_git_dir(".", 0);
check_repository_format();
return path;
}

18
setup.c
View file

@ -725,7 +725,7 @@ static const char *setup_explicit_git_dir(const char *gitdirenv,
}
/* #18, #26 */
set_git_dir(gitdirenv);
set_git_dir(gitdirenv, 0);
free(gitfile);
return NULL;
}
@ -747,7 +747,7 @@ static const char *setup_explicit_git_dir(const char *gitdirenv,
}
else if (!git_env_bool(GIT_IMPLICIT_WORK_TREE_ENVIRONMENT, 1)) {
/* #16d */
set_git_dir(gitdirenv);
set_git_dir(gitdirenv, 0);
free(gitfile);
return NULL;
}
@ -759,14 +759,14 @@ static const char *setup_explicit_git_dir(const char *gitdirenv,
/* both get_git_work_tree() and cwd are already normalized */
if (!strcmp(cwd->buf, worktree)) { /* cwd == worktree */
set_git_dir(gitdirenv);
set_git_dir(gitdirenv, 0);
free(gitfile);
return NULL;
}
offset = dir_inside_of(cwd->buf, worktree);
if (offset >= 0) { /* cwd inside worktree? */
set_git_dir(real_path(gitdirenv));
set_git_dir(gitdirenv, 1);
if (chdir(worktree))
die_errno(_("cannot chdir to '%s'"), worktree);
strbuf_addch(cwd, '/');
@ -775,7 +775,7 @@ static const char *setup_explicit_git_dir(const char *gitdirenv,
}
/* cwd outside worktree */
set_git_dir(gitdirenv);
set_git_dir(gitdirenv, 0);
free(gitfile);
return NULL;
}
@ -804,7 +804,7 @@ static const char *setup_discovered_git_dir(const char *gitdir,
/* #16.2, #17.2, #20.2, #21.2, #24, #25, #28, #29 (see t1510) */
if (is_bare_repository_cfg > 0) {
set_git_dir(offset == cwd->len ? gitdir : real_path(gitdir));
set_git_dir(gitdir, (offset != cwd->len));
if (chdir(cwd->buf))
die_errno(_("cannot come back to cwd"));
return NULL;
@ -813,7 +813,7 @@ static const char *setup_discovered_git_dir(const char *gitdir,
/* #0, #1, #5, #8, #9, #12, #13 */
set_git_work_tree(".");
if (strcmp(gitdir, DEFAULT_GIT_DIR_ENVIRONMENT))
set_git_dir(gitdir);
set_git_dir(gitdir, 0);
inside_git_dir = 0;
inside_work_tree = 1;
if (offset >= cwd->len)
@ -856,10 +856,10 @@ static const char *setup_bare_git_dir(struct strbuf *cwd, int offset,
die_errno(_("cannot come back to cwd"));
root_len = offset_1st_component(cwd->buf);
strbuf_setlen(cwd, offset > root_len ? offset : root_len);
set_git_dir(cwd->buf);
set_git_dir(cwd->buf, 0);
}
else
set_git_dir(".");
set_git_dir(".", 0);
return NULL;
}