From 2f55cc471e41028d08bd6ac33c25c1b587bb2660 Mon Sep 17 00:00:00 2001 From: Bill Zissimopoulos Date: Thu, 28 May 2020 16:35:57 -0700 Subject: [PATCH] mingw: lstat: compute correct size for symlinks This commit fixes mingw_lstat by computing the proper size for symlinks according to POSIX. POSIX specifies that upon successful return from lstat: "the value of the st_size member shall be set to the length of the pathname contained in the symbolic link not including any terminating null byte". Prior to this commit the mingw_lstat function returned a fixed size of 4096. This caused problems in git repositories that were accessed by git for Cygwin or git for WSL. For example, doing `git reset --hard` using git for Windows would update the size of symlinks in the index to be 4096; at a later time git for Cygwin or git for WSL would find that symlinks have changed size during `git status`. Vice versa doing `git reset --hard` in git for Cygwin or git for WSL would update the size of symlinks in the index with the correct value, only for git for Windows to find incorrectly at a later time that the size had changed. Additional fixup by: Johannes Schindelin Signed-off-by: Bill Zissimopoulos --- compat/mingw.c | 65 ++++++++++++++++++++++++++++++++++---------------- 1 file changed, 44 insertions(+), 21 deletions(-) diff --git a/compat/mingw.c b/compat/mingw.c index e592e635290d80..b85485a97ccc71 100644 --- a/compat/mingw.c +++ b/compat/mingw.c @@ -969,10 +969,14 @@ static int has_valid_directory_prefix(wchar_t *wfilename) return 1; } +static int readlink_1(const WCHAR *wpath, BOOL fail_on_unknown_tag, + char *tmpbuf, int *plen, DWORD *ptag); + int mingw_lstat(const char *file_name, struct stat *buf) { WIN32_FILE_ATTRIBUTE_DATA fdata; - WIN32_FIND_DATAW findbuf = { 0 }; + DWORD reparse_tag = 0; + int link_len = 0; wchar_t wfilename[MAX_LONG_PATH]; int wlen = xutftowcs_long_path(wfilename, file_name); if (wlen < 0) @@ -987,20 +991,21 @@ int mingw_lstat(const char *file_name, struct stat *buf) } if (GetFileAttributesExW(wfilename, GetFileExInfoStandard, &fdata)) { - /* for reparse points, use FindFirstFile to get the reparse tag */ + /* for reparse points, get the link tag and length */ if (fdata.dwFileAttributes & FILE_ATTRIBUTE_REPARSE_POINT) { - HANDLE handle = FindFirstFileW(wfilename, &findbuf); - if (handle == INVALID_HANDLE_VALUE) - goto error; - FindClose(handle); + char tmpbuf[MAX_LONG_PATH]; + + if (readlink_1(wfilename, FALSE, tmpbuf, &link_len, + &reparse_tag) < 0) + return -1; } buf->st_ino = 0; buf->st_gid = 0; buf->st_uid = 0; buf->st_nlink = 1; buf->st_mode = file_attr_to_st_mode(fdata.dwFileAttributes, - findbuf.dwReserved0, file_name); - buf->st_size = S_ISLNK(buf->st_mode) ? MAX_LONG_PATH : + reparse_tag, file_name); + buf->st_size = S_ISLNK(buf->st_mode) ? link_len : fdata.nFileSizeLow | (((off_t) fdata.nFileSizeHigh) << 32); buf->st_dev = buf->st_rdev = 0; /* not used by Git */ filetime_to_timespec(&(fdata.ftLastAccessTime), &(buf->st_atim)); @@ -1008,7 +1013,7 @@ int mingw_lstat(const char *file_name, struct stat *buf) filetime_to_timespec(&(fdata.ftCreationTime), &(buf->st_ctim)); return 0; } -error: + switch (GetLastError()) { case ERROR_ACCESS_DENIED: case ERROR_SHARING_VIOLATION: @@ -2968,17 +2973,13 @@ typedef struct _REPARSE_DATA_BUFFER { } REPARSE_DATA_BUFFER, *PREPARSE_DATA_BUFFER; #endif -int readlink(const char *path, char *buf, size_t bufsiz) +static int readlink_1(const WCHAR *wpath, BOOL fail_on_unknown_tag, + char *tmpbuf, int *plen, DWORD *ptag) { HANDLE handle; - WCHAR wpath[MAX_LONG_PATH], *wbuf; + WCHAR *wbuf; REPARSE_DATA_BUFFER *b = alloca(MAXIMUM_REPARSE_DATA_BUFFER_SIZE); DWORD dummy; - char tmpbuf[MAX_LONG_PATH]; - int len; - - if (xutftowcs_long_path(wpath, path) < 0) - return -1; /* read reparse point data */ handle = CreateFileW(wpath, 0, @@ -2998,7 +2999,7 @@ int readlink(const char *path, char *buf, size_t bufsiz) CloseHandle(handle); /* get target path for symlinks or mount points (aka 'junctions') */ - switch (b->ReparseTag) { + switch ((*ptag = b->ReparseTag)) { case IO_REPARSE_TAG_SYMLINK: wbuf = (WCHAR*) (((char*) b->SymbolicLinkReparseBuffer.PathBuffer) + b->SymbolicLinkReparseBuffer.SubstituteNameOffset); @@ -3012,10 +3013,34 @@ int readlink(const char *path, char *buf, size_t bufsiz) + b->MountPointReparseBuffer.SubstituteNameLength) = 0; break; default: - errno = EINVAL; - return -1; + if (fail_on_unknown_tag) { + errno = EINVAL; + return -1; + } else { + *plen = MAX_LONG_PATH; + return 0; + } } + if ((*plen = + xwcstoutf(tmpbuf, normalize_ntpath(wbuf), MAX_LONG_PATH)) < 0) + return -1; + return 0; +} + +int readlink(const char *path, char *buf, size_t bufsiz) +{ + WCHAR wpath[MAX_LONG_PATH]; + char tmpbuf[MAX_LONG_PATH]; + int len; + DWORD tag; + + if (xutftowcs_long_path(wpath, path) < 0) + return -1; + + if (readlink_1(wpath, TRUE, tmpbuf, &len, &tag) < 0) + return -1; + /* * Adapt to strange readlink() API: Copy up to bufsiz *bytes*, potentially * cutting off a UTF-8 sequence. Insufficient bufsize is *not* a failure @@ -3023,8 +3048,6 @@ int readlink(const char *path, char *buf, size_t bufsiz) * so convert to a (hopefully large enough) temporary buffer, then memcpy * the requested number of bytes (including '\0' for robustness). */ - if ((len = xwcstoutf(tmpbuf, normalize_ntpath(wbuf), MAX_LONG_PATH)) < 0) - return -1; memcpy(buf, tmpbuf, min(bufsiz, len + 1)); return min(bufsiz, len); }