From 15d6f564cde65fedf46423eea0a64d17b299bb2f Mon Sep 17 00:00:00 2001 From: Corinna Vinschen Date: Tue, 12 Jan 2016 15:23:14 +0100 Subject: Try loading with safe path using LOAD_LIBRARY_SEARCH_SYSTEM32 first * autoload.cc (dll_load): Move safe loading from std_dll_init here. Add code to handle systems supporting LOAD_LIBRARY_SEARCH flags. Add comments to explain what the code is doing. Fix up comment preceeding this function. (std_dll_init): Move safe loading code to dll_load. * wincap.h (wincaps::has_load_lib_search_flags): New element. * wincap.cc: Implement above element throughout. Signed-off-by: Corinna Vinschen --- winsup/cygwin/autoload.cc | 52 +++++++++++++++++++++++++++++++---------------- 1 file changed, 34 insertions(+), 18 deletions(-) (limited to 'winsup/cygwin/autoload.cc') diff --git a/winsup/cygwin/autoload.cc b/winsup/cygwin/autoload.cc index 836597da8..7158e952b 100644 --- a/winsup/cygwin/autoload.cc +++ b/winsup/cygwin/autoload.cc @@ -333,20 +333,44 @@ union retchain }; -/* This function is a workaround for the problem reported here: +/* This function handles the problem described here: + + http://www.microsoft.com/technet/security/advisory/2269637.mspx + https://msdn.microsoft.com/library/ff919712 + + It also contains a workaround for the problem reported here: http://cygwin.com/ml/cygwin/2011-02/msg00552.html and discussed here: http://cygwin.com/ml/cygwin-developers/2011-02/threads.html#00007 To wit: winmm.dll calls FreeLibrary in its DllMain and that can result - in LoadLibraryExW returning an ERROR_INVALID_ADDRESS. */ + in LoadLibraryExW returning an ERROR_INVALID_ADDRESS. */ static __inline bool -dll_load (HANDLE& handle, WCHAR *name) +dll_load (HANDLE& handle, PWCHAR name) { - HANDLE h = LoadLibraryW (name); - if (!h && handle && wincap.use_dont_resolve_hack () - && GetLastError () == ERROR_INVALID_ADDRESS) - h = LoadLibraryExW (name, NULL, DONT_RESOLVE_DLL_REFERENCES); + HANDLE h; + + /* On systems supporting LOAD_LIBRARY_SEARCH flags, try to load + explicitely from the system dir first. */ + if (wincap.has_load_lib_search_flags ()) + h = LoadLibraryExW (name, NULL, LOAD_LIBRARY_SEARCH_SYSTEM32); + if (!h) + { + WCHAR dll_path[MAX_PATH]; + + /* If that failed, try loading with full path, which sometimes + fails for no good reason. */ + wcpcpy (wcpcpy (dll_path, windows_system_directory), name); + h = LoadLibraryW (dll_path); + /* If that failed according to the second problem outlined in the + comment preceeding this function. */ + if (!h && handle && wincap.use_dont_resolve_hack () + && GetLastError () == ERROR_INVALID_ADDRESS) + h = LoadLibraryExW (dll_path, NULL, DONT_RESOLVE_DLL_REFERENCES); + /* Last resort: Try loading just by name. */ + if (!h) + h = LoadLibraryW (name); + } if (!h) return false; handle = h; @@ -420,18 +444,15 @@ std_dll_init () { fenv_t fpuenv; fegetenv (&fpuenv); - WCHAR dll_path[MAX_PATH]; DWORD err = ERROR_SUCCESS; int i; - /* http://www.microsoft.com/technet/security/advisory/2269637.mspx */ - wcpcpy (wcpcpy (dll_path, windows_system_directory), dll->name); /* MSDN seems to imply that LoadLibrary can fail mysteriously, so, since there have been reports of this in the mailing list, retry several times before giving up. */ for (i = 1; i <= RETRY_COUNT; i++) { /* If loading the library succeeds, just leave the loop. */ - if (dll_load (dll->handle, dll_path)) + if (dll_load (dll->handle, dll->name)) break; /* Otherwise check error code returned by LoadLibrary. If the error code is neither NOACCESS nor DLL_INIT_FAILED, break out @@ -444,15 +465,10 @@ std_dll_init () } if ((uintptr_t) dll->handle <= 1) { - /* If LoadLibrary with full path returns one of the weird errors - reported on the Cygwin mailing list, retry with only the DLL - name. Only do this when the above retry loop has been exhausted. */ - if (i > RETRY_COUNT && dll_load (dll->handle, dll->name)) - /* got it with the fallback */; - else if ((func->decoration & 1)) + if ((func->decoration & 1)) dll->handle = INVALID_HANDLE_VALUE; else - api_fatal ("unable to load %W, %E", dll_path); + api_fatal ("unable to load %W, %E", dll->name); } fesetenv (&fpuenv); } -- cgit v1.2.3