From 0be0b8f0335ec0fad6188b3570dffeba4ec94fea Mon Sep 17 00:00:00 2001 From: Corinna Vinschen Date: Sat, 9 Feb 2019 15:36:02 +0100 Subject: [PATCH] Cygwin: execve: fix setting O_APPEND file offset for native child dtable::set_file_pointers_for_exec is called from child_info_spawn::worker to move the file position of O_APPEND files to EOF if the child is a native child. However, this only works correctly for the first O_APPEND file descriptor: - set_file_pointers_for_exec calls SetFilePointer. The higher 4 bytes of the desired file offset are given to SetFilePointer as pointer to a DWORD value. On return, SetFilePointer returns the higher 4 bytes of the new file position in this DWORD. - So for the second and subsequent descriptors the higher 4 byte of the file position depend on what the actual file position of the previous file has been set to: - If the file is > 2 Gigs, the high offset will not be 0 anymore. - If the desciptor points to a non-seekable file (i.e., a pipe or socket), SetFilePosition returns an error and sets the high position to -1. Fix this by calling SetFilePointerEx instead, which does not modify the incoming position value. Signed-off-by: Corinna Vinschen --- winsup/cygwin/dtable.cc | 5 +++-- winsup/cygwin/release/3.0 | 3 +++ 2 files changed, 6 insertions(+), 2 deletions(-) diff --git a/winsup/cygwin/dtable.cc b/winsup/cygwin/dtable.cc index 663f99b34..86e0c716d 100644 --- a/winsup/cygwin/dtable.cc +++ b/winsup/cygwin/dtable.cc @@ -857,12 +857,13 @@ dtable::set_file_pointers_for_exec () { /* This is not POSIX-compliant so the function is only called for non-Cygwin processes. */ - LONG off_high = 0; + LARGE_INTEGER eof = { QuadPart: 0 }; + lock (); fhandler_base *fh; for (size_t i = 0; i < size; i++) if ((fh = fds[i]) != NULL && fh->get_flags () & O_APPEND) - SetFilePointer (fh->get_handle (), 0, &off_high, FILE_END); + SetFilePointerEx (fh->get_handle (), eof, NULL, FILE_END); unlock (); } diff --git a/winsup/cygwin/release/3.0 b/winsup/cygwin/release/3.0 index 4cd422a56..da0fe0961 100644 --- a/winsup/cygwin/release/3.0 +++ b/winsup/cygwin/release/3.0 @@ -100,3 +100,6 @@ Bug Fixes - Fix exception handling in pthreads. Addresses: https://cygwin.com/ml/cygwin/2019-01/msg00149.html + +- Fix O_APPEND handling on files when calling non-Cygwin applications + Addresses: https://cygwin.com/ml/cygwin/2019-02/msg00081.html -- 2.43.5