Commit d83b2e9f51539287d5d2b1bd939ea9540fa6e5be
2015-09-05T03:54:06
filebuf: follow symlinks when creating a lock file We create a lockfile to update files under GIT_DIR. Sometimes these files are actually located elsewhere and a symlink takes their place. In that case we should lock and update the file at its final location rather than overwrite the symlink.
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diff --git a/CHANGELOG.md b/CHANGELOG.md
index 8f28cbf..1f3c3ed 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,9 @@ v0.23 + 1
example `filter=*`. Consumers should examine the attributes parameter
of the `check` function for details.
+* Symlinks are now followed when locking a file, which can be
+ necessary when multiple worktrees share a base repository.
+
### API additions
* `git_config_lock()` has been added, which allow for
diff --git a/src/filebuf.c b/src/filebuf.c
index 838f4b4..2bbc210 100644
--- a/src/filebuf.c
+++ b/src/filebuf.c
@@ -191,6 +191,81 @@ static int write_deflate(git_filebuf *file, void *source, size_t len)
return 0;
}
+#define MAX_SYMLINK_DEPTH 5
+
+static int resolve_symlink(git_buf *out, const char *path)
+{
+ int i, error, root;
+ ssize_t ret;
+ struct stat st;
+ git_buf curpath = GIT_BUF_INIT, target = GIT_BUF_INIT;
+
+ if ((error = git_buf_grow(&target, GIT_PATH_MAX + 1)) < 0 ||
+ (error = git_buf_puts(&curpath, path)) < 0)
+ return error;
+
+ for (i = 0; i < MAX_SYMLINK_DEPTH; i++) {
+ error = p_lstat(curpath.ptr, &st);
+ if (error < 0 && errno == ENOENT) {
+ error = git_buf_puts(out, curpath.ptr);
+ goto cleanup;
+ }
+
+ if (error < 0) {
+ giterr_set(GITERR_OS, "failed to stat '%s'", curpath.ptr);
+ error = -1;
+ goto cleanup;
+ }
+
+ if (!S_ISLNK(st.st_mode)) {
+ error = git_buf_puts(out, curpath.ptr);
+ goto cleanup;
+ }
+
+ ret = p_readlink(curpath.ptr, target.ptr, GIT_PATH_MAX);
+ if (ret < 0) {
+ giterr_set(GITERR_OS, "failed to read symlink '%s'", curpath.ptr);
+ error = -1;
+ goto cleanup;
+ }
+
+ if (ret == GIT_PATH_MAX) {
+ giterr_set(GITERR_INVALID, "symlink target too long");
+ error = -1;
+ goto cleanup;
+ }
+
+ /* readlink(2) won't NUL-terminate for us */
+ target.ptr[ret] = '\0';
+ target.size = ret;
+
+ root = git_path_root(target.ptr);
+ if (root >= 0) {
+ if ((error = git_buf_puts(&curpath, target.ptr)) < 0)
+ goto cleanup;
+ } else {
+ git_buf dir = GIT_BUF_INIT;
+
+ if ((error = git_path_dirname_r(&dir, curpath.ptr)) < 0)
+ goto cleanup;
+
+ git_buf_swap(&curpath, &dir);
+ git_buf_free(&dir);
+
+ if ((error = git_path_apply_relative(&curpath, target.ptr)) < 0)
+ goto cleanup;
+ }
+ }
+
+ giterr_set(GITERR_INVALID, "maximum symlink depth reached");
+ error = -1;
+
+cleanup:
+ git_buf_free(&curpath);
+ git_buf_free(&target);
+ return error;
+}
+
int git_filebuf_open(git_filebuf *file, const char *path, int flags, mode_t mode)
{
int compression, error = -1;
@@ -265,11 +340,14 @@ int git_filebuf_open(git_filebuf *file, const char *path, int flags, mode_t mode
file->path_lock = git_buf_detach(&tmp_path);
GITERR_CHECK_ALLOC(file->path_lock);
} else {
- path_len = strlen(path);
+ git_buf resolved_path = GIT_BUF_INIT;
+
+ if ((error = resolve_symlink(&resolved_path, path)) < 0)
+ goto cleanup;
/* Save the original path of the file */
- file->path_original = git__strdup(path);
- GITERR_CHECK_ALLOC(file->path_original);
+ path_len = resolved_path.size;
+ file->path_original = git_buf_detach(&resolved_path);
/* create the locking path by appending ".lock" to the original */
GITERR_CHECK_ALLOC_ADD(&alloc_len, path_len, GIT_FILELOCK_EXTLENGTH);
diff --git a/tests/core/filebuf.c b/tests/core/filebuf.c
index 3f7dc85..39d98ff 100644
--- a/tests/core/filebuf.c
+++ b/tests/core/filebuf.c
@@ -151,3 +151,56 @@ void test_core_filebuf__rename_error(void)
cl_assert_equal_i(false, git_path_exists(test_lock));
}
+
+void test_core_filebuf__symlink_follow(void)
+{
+ git_filebuf file = GIT_FILEBUF_INIT;
+ const char *dir = "linkdir", *source = "linkdir/link";
+
+#ifdef GIT_WIN32
+ cl_skip();
+#endif
+
+ cl_git_pass(p_mkdir(dir, 0777));
+ cl_git_pass(p_symlink("target", source));
+
+ cl_git_pass(git_filebuf_open(&file, source, 0, 0666));
+ cl_git_pass(git_filebuf_printf(&file, "%s\n", "libgit2 rocks"));
+
+ cl_assert_equal_i(true, git_path_exists("linkdir/target.lock"));
+
+ cl_git_pass(git_filebuf_commit(&file));
+ cl_assert_equal_i(true, git_path_exists("linkdir/target"));
+
+ git_filebuf_cleanup(&file);
+
+ /* The second time around, the target file does exist */
+ cl_git_pass(git_filebuf_open(&file, source, 0, 0666));
+ cl_git_pass(git_filebuf_printf(&file, "%s\n", "libgit2 rocks"));
+
+ cl_assert_equal_i(true, git_path_exists("linkdir/target.lock"));
+
+ cl_git_pass(git_filebuf_commit(&file));
+ cl_assert_equal_i(true, git_path_exists("linkdir/target"));
+
+ git_filebuf_cleanup(&file);
+ cl_git_pass(git_futils_rmdir_r(dir, NULL, GIT_RMDIR_REMOVE_FILES));
+}
+
+void test_core_filebuf__symlink_depth(void)
+{
+ git_filebuf file = GIT_FILEBUF_INIT;
+ const char *dir = "linkdir", *source = "linkdir/link";
+
+#ifdef GIT_WIN32
+ cl_skip();
+#endif
+
+ cl_git_pass(p_mkdir(dir, 0777));
+ /* Endless loop */
+ cl_git_pass(p_symlink("link", source));
+
+ cl_git_fail(git_filebuf_open(&file, source, 0, 0666));
+
+ cl_git_pass(git_futils_rmdir_r(dir, NULL, GIT_RMDIR_REMOVE_FILES));
+}