set_git_dir: fix crash when used with real_path()

`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>

diff --git a/builtin/init-db.c b/builtin/init-db.c
index 944ec77fe1032775ff595f0b1eb99a1fb22d059f..5bf61a7e05662325f952c01149bf9328f4ff9ab4 100644 (file)
--- a/builtin/init-db.c
+++ b/builtin/init-db.c
@@ -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;

diff --git a/cache.h b/cache.h
index 37c899b53f7c3d36f1145d33f19d5c8302b911f5..8cee257d3d73a5d2ac58a5a4f8f051bd505c0398 100644 (file)
--- a/cache.h
+++ b/cache.h
@@ -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);

diff --git a/environment.c b/environment.c
index e72a02d0d577dab4da0f559ed988899baff91fbc..c436de31eef12946ee3223c06a4490df9c9dd49d 100644 (file)
--- a/environment.c
+++ b/environment.c
@@ -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)

diff --git a/path.c b/path.c
index 88cf59300738a2f10750ff458fa35b1211f00ab8..c5a8fe4f0c3c1273f6e6489077098d349fa101f3 100644 (file)
--- a/path.c
+++ b/path.c
@@ -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;
        }

diff --git a/setup.c b/setup.c
index 4ea7a0b081bfd20a87d413d887f6d6926dbde8ab..fa4317e707a0ebf6629042cecee7a87a56e266dd 100644 (file)
--- a/setup.c
+++ b/setup.c
@@ -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;
 }