From 6d898f43fc87a7bf3ab100d75538e381bd86f657 Mon Sep 17 00:00:00 2001 From: Corinna Vinschen Date: Fri, 19 Feb 2021 18:15:58 +0100 Subject: [PATCH] Cygwin: realpath: fix cygwin installation dir being access via junction Consider this case: - Cygwin installed in C:\cygwin64 - mklink /j D:\cygwin64 C:\cygwin64 - create testcase calling realpath("/", result); printf ("%s\n", result); - start cmd >C:\cygwin64\bin\bash -lc / >D\cygwin64\bin\bash -lc /cygdrive/c/cygwin64 This scenario circumventing the mount point handling which is automated in terms of /, depending on the path returned from GetModuleFileNameW for the Cygwin DLL. When calling D:\cygwin64\bin\bash the dir returned from GetModuleFileNameW is D:\cygwin64\bin, thus root is D:\cygwin64. However, junctions are treated as symlinks in Cygwin which explains why the path gets converted to a cygdrive path. Fix this by calling GetFinalPathNameByHandleW on the result from GetModuleFileNameW to get the correct root path, even if accessed via a junction point. Signed-off-by: Corinna Vinschen --- winsup/cygwin/cygheap.cc | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/winsup/cygwin/cygheap.cc b/winsup/cygwin/cygheap.cc index 3a32c352d..01b49468e 100644 --- a/winsup/cygwin/cygheap.cc +++ b/winsup/cygwin/cygheap.cc @@ -144,6 +144,19 @@ init_cygheap::init_installation_root () api_fatal ("Can't initialize Cygwin installation root dir.\n" "GetModuleFileNameW(%p, %p, %u), %E", cygwin_hmodule, installation_root_buf, PATH_MAX); + + /* We don't care if fetching the final pathname fails, it's non-fatal and + the path returned by GetModuleFileNameW is still valid. */ + HANDLE h; + h = CreateFileW (installation_root_buf, GENERIC_READ, FILE_SHARE_VALID_FLAGS, + &sec_none, OPEN_EXISTING, 0, 0); + if (h != INVALID_HANDLE_VALUE) + { + GetFinalPathNameByHandleW (h, installation_root_buf, PATH_MAX, + FILE_NAME_NORMALIZED); + CloseHandle (h); + } + PWCHAR p = installation_root_buf; if (wcsncasecmp (p, L"\\\\", 2)) /* Normal drive letter path */ { -- 2.43.5