[FFmpeg-devel] [PATCH v9 3/6] compat/w32dlfcn.h: Remove MAX_PATH limit and replace LoadLibraryExA with LoadLibraryExW
Martin Storsjö
martin at martin.st
Wed Apr 20 14:33:41 EEST 2022
On Fri, 15 Apr 2022, Nil Admirari wrote:
> ---
> compat/w32dlfcn.h | 78 ++++++++++++++++++++++++++++++++++++++---------
> 1 file changed, 64 insertions(+), 14 deletions(-)
>
> diff --git a/compat/w32dlfcn.h b/compat/w32dlfcn.h
> index 52a94efa..0f41f50b 100644
> --- a/compat/w32dlfcn.h
> +++ b/compat/w32dlfcn.h
> @@ -25,6 +25,30 @@
> #if (_WIN32_WINNT < 0x0602) || HAVE_WINRT
> #include "libavutil/wchar_filename.h"
> #endif
> +
> +static inline wchar_t *get_module_filename(const HMODULE module)
> +{
> + wchar_t *path = NULL, *new_path = NULL;
> + DWORD path_size = 0, path_len = 0;
> +
> + do {
> + path_size = path_size ? 2 * path_size : MAX_PATH;
> + new_path = av_realloc_array(path, path_size, sizeof *path);
> + if (!new_path) {
> + av_free(path);
> + return NULL;
> + }
> + path = new_path;
> + path_len = GetModuleFileNameW(module, path, path_size);
> + } while (path_len && path_size <= 32768 && path_size <= path_len);
> +
> + if (!path_len) {
> + av_free(path);
> + return NULL;
> + }
> + return path;
> +}
> +
> /**
> * Safe function used to open dynamic libs. This attempts to improve program security
> * by removing the current directory from the dll search path. Only dll's found in the
> @@ -34,29 +58,53 @@
> */
> static inline HMODULE win32_dlopen(const char *name)
> {
> + wchar_t *name_w = NULL;
> + if (utf8towchar(name, &name_w))
> + name_w = NULL;
> #if _WIN32_WINNT < 0x0602
> // Need to check if KB2533623 is available
> if (!GetProcAddress(GetModuleHandleW(L"kernel32.dll"), "SetDefaultDllDirectories")) {
> HMODULE module = NULL;
> - wchar_t *path = NULL, *name_w = NULL;
> - DWORD pathlen;
> - if (utf8towchar(name, &name_w))
> + wchar_t *path = NULL, *new_path = NULL;
> + DWORD pathlen, pathsize, namelen;
> + if (!name_w)
> goto exit;
> - path = (wchar_t *)av_calloc(MAX_PATH, sizeof(wchar_t));
> + namelen = wcslen(name_w);
> // Try local directory first
> - pathlen = GetModuleFileNameW(NULL, path, MAX_PATH);
> - pathlen = wcsrchr(path, '\\') - path;
> - if (pathlen == 0 || pathlen + wcslen(name_w) + 2 > MAX_PATH)
> + path = get_module_filename(NULL);
> + if (!path)
> goto exit;
> - path[pathlen] = '\\';
> + new_path = wcsrchr(path, '\\');
> + if (!new_path)
> + goto exit;
> + pathlen = new_path - path;
> + pathsize = pathlen + namelen + 2;
> + new_path = av_realloc_array(path, pathsize, sizeof *path);
> + if (!new_path)
> + goto exit;
> + path = new_path;
> wcscpy(path + pathlen + 1, name_w);
> module = LoadLibraryExW(path, NULL, LOAD_WITH_ALTERED_SEARCH_PATH);
> if (module == NULL) {
> // Next try System32 directory
> - pathlen = GetSystemDirectoryW(path, MAX_PATH);
> - if (pathlen == 0 || pathlen + wcslen(name_w) + 2 > MAX_PATH)
> + pathlen = GetSystemDirectoryW(path, pathsize);
> + if (!pathlen)
> goto exit;
> - path[pathlen] = '\\';
> + // Buffer is not enough in two cases:
> + // 1. system directory + \ + module name
> + // 2. system directory even without module name.
> + if (pathlen + namelen + 2 > pathsize) {
> + pathsize = pathlen + namelen + 2;
> + new_path = av_realloc_array(path, pathsize, sizeof *path);
> + if (!new_path)
> + goto exit;
> + path = new_path;
> + // Query again to handle case #2.
> + pathlen = GetSystemDirectoryW(path, pathsize);
> + if (!pathlen)
> + goto exit;
> + }
> + path[pathlen] = L'\\';
> wcscpy(path + pathlen + 1, name_w);
> module = LoadLibraryExW(path, NULL, LOAD_WITH_ALTERED_SEARCH_PATH);
> }
> @@ -73,15 +121,17 @@ exit:
> # define LOAD_LIBRARY_SEARCH_SYSTEM32 0x00000800
> #endif
> #if HAVE_WINRT
> - wchar_t *name_w = NULL;
> int ret;
> - if (utf8towchar(name, &name_w))
> + if (!name_w)
> return NULL;
> ret = LoadPackagedLibrary(name_w, 0);
> av_free(name_w);
> return ret;
> #else
> - return LoadLibraryExA(name, NULL, LOAD_LIBRARY_SEARCH_APPLICATION_DIR | LOAD_LIBRARY_SEARCH_SYSTEM32);
> + /* filename may be be in CP_ACP */
> + if (!name_w)
> + return LoadLibraryExA(name, NULL, LOAD_LIBRARY_SEARCH_APPLICATION_DIR | LOAD_LIBRARY_SEARCH_SYSTEM32);
> + return LoadLibraryExW(name_w, NULL, LOAD_LIBRARY_SEARCH_APPLICATION_DIR | LOAD_LIBRARY_SEARCH_SYSTEM32);
> #endif
> }
> #define dlopen(name, flags) win32_dlopen(name)
> --
> 2.32.0
This looks ok to me.
// Martin
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