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From: Corinna Vinschen <corinna@sourceware.org> To: cygwin-cvs@sourceware.org Subject: [newlib-cygwin] Cygwin: Make native clipboard layout same for 32- and 64-bit Date: Tue, 26 Oct 2021 10:42:28 +0000 (GMT) [thread overview] Message-ID: <20211026104228.6390C3858410@sourceware.org> (raw) https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=23b1400f83a5f64dfab60cba2e25b0d858f44b5c commit 23b1400f83a5f64dfab60cba2e25b0d858f44b5c Author: Mark Geisert <mark@maxrnd.com> Date: Mon Oct 25 02:25:40 2021 -0700 Cygwin: Make native clipboard layout same for 32- and 64-bit This patch unifies the layout of the clipboard descriptor cygcb_t for 32- and 64-bit Cygwin. It allows correct copy/paste between the two environments without corruption of user's copied data and without access violations due to interpreting that data as a size field. The definitions of CYGWIN_NATIVE and cygcb_t are moved to a new include file, sys/clipboard.h. The include file is used by fhandler_clipboard.cc as well as getclip.c and putclip.c in the Cygwin cygutils package. When copy/pasting between 32- and 64-bit Cygwin environments, both must be running version 3.3.0 or later for successful operation. Diff: --- winsup/cygwin/fhandler_clipboard.cc | 42 ++++++++++++++++++------------ winsup/cygwin/include/sys/clipboard.h | 49 +++++++++++++++++++++++++++++++++++ winsup/cygwin/release/3.3.0 | 4 +++ 3 files changed, 78 insertions(+), 17 deletions(-) diff --git a/winsup/cygwin/fhandler_clipboard.cc b/winsup/cygwin/fhandler_clipboard.cc index ccdb295f3..0b87dd352 100644 --- a/winsup/cygwin/fhandler_clipboard.cc +++ b/winsup/cygwin/fhandler_clipboard.cc @@ -17,6 +17,7 @@ details. */ #include "dtable.h" #include "cygheap.h" #include "child_info.h" +#include <sys/clipboard.h> /* * Robert Collins: @@ -24,15 +25,6 @@ details. */ * changed? How does /dev/clipboard operate under (say) linux? */ -static const WCHAR *CYGWIN_NATIVE = L"CYGWIN_NATIVE_CLIPBOARD"; - -typedef struct -{ - timestruc_t timestamp; - size_t len; - char data[1]; -} cygcb_t; - fhandler_dev_clipboard::fhandler_dev_clipboard () : fhandler_base (), pos (0), membuffer (NULL), msize (0) { @@ -74,9 +66,17 @@ fhandler_dev_clipboard::set_clipboard (const void *buf, size_t len) } clipbuf = (cygcb_t *) GlobalLock (hmem); - clock_gettime (CLOCK_REALTIME, &clipbuf->timestamp); - clipbuf->len = len; - memcpy (clipbuf->data, buf, len); + clock_gettime (CLOCK_REALTIME, &clipbuf->ts); +#ifdef __x86_64__ + /* ts overlays cb_sec and cb_nsec such that no conversion is needed */ +#elif __i386__ + /* Expand 32-bit timespec layout to 64-bit layout. + NOTE: Steps must be done in this order to avoid data loss. */ + clipbuf->cb_nsec = clipbuf->ts.tv_nsec; + clipbuf->cb_sec = clipbuf->ts.tv_sec; +#endif + clipbuf->cb_size = len; + memcpy (&clipbuf[1], buf, len); // append user-supplied data GlobalUnlock (hmem); EmptyClipboard (); @@ -179,8 +179,16 @@ fhandler_dev_clipboard::fstat (struct stat *buf) && (hglb = GetClipboardData (format)) && (clipbuf = (cygcb_t *) GlobalLock (hglb))) { - buf->st_atim = buf->st_mtim = clipbuf->timestamp; - buf->st_size = clipbuf->len; +#ifdef __x86_64__ + /* ts overlays cb_sec and cb_nsec such that no conversion is needed */ +#elif __i386__ + /* Compress 64-bit timespec layout to 32-bit layout. + NOTE: Steps must be done in this order to avoid data loss. */ + clipbuf->ts.tv_sec = clipbuf->cb_sec; + clipbuf->ts.tv_nsec = clipbuf->cb_nsec; +#endif + buf->st_atim = buf->st_mtim = clipbuf->ts; + buf->st_size = clipbuf->cb_size; GlobalUnlock (hglb); } CloseClipboard (); @@ -218,10 +226,10 @@ fhandler_dev_clipboard::read (void *ptr, size_t& len) { cygcb_t *clipbuf = (cygcb_t *) cb_data; - if (pos < (off_t) clipbuf->len) + if (pos < (off_t) clipbuf->cb_size) { - ret = ((len > (clipbuf->len - pos)) ? (clipbuf->len - pos) : len); - memcpy (ptr, clipbuf->data + pos , ret); + ret = (len > (clipbuf->cb_size - pos)) ? clipbuf->cb_size - pos : len; + memcpy (ptr, &clipbuf[1] + pos , ret); pos += ret; } } diff --git a/winsup/cygwin/include/sys/clipboard.h b/winsup/cygwin/include/sys/clipboard.h new file mode 100644 index 000000000..4c00c8ea1 --- /dev/null +++ b/winsup/cygwin/include/sys/clipboard.h @@ -0,0 +1,49 @@ +/* sys/clipboard.h + +This file is part of Cygwin. + +This software is a copyrighted work licensed under the terms of the +Cygwin license. Please consult the file "CYGWIN_LICENSE" for +details. */ + +#ifndef _SYS_CLIPBOARD_H_ +#define _SYS_CLIPBOARD_H_ + +/* + * These definitions are used in fhandler_clipboard.cc + * as well as in the Cygwin cygutils package, specifically + * getclip.c and putclip.c. + */ + +static const WCHAR *CYGWIN_NATIVE = L"CYGWIN_NATIVE_CLIPBOARD"; + +/* + * The following layout of cygcb_t is new with Cygwin 3.3.0. It aids in the + * transfer of clipboard contents between 32- and 64-bit Cygwin environments. + */ +typedef struct +{ + union + { + /* + * Note that ts below overlays the struct following it. On 32-bit Cygwin + * timespec values have to be converted to|from cygcb_t layout. On 64-bit + * Cygwin timespec values perfectly conform to the struct following, so + * no conversion is needed. + * + * We avoid directly using 'struct timespec' or 'size_t' here because they + * are different sizes on different architectures. When copy/pasting + * between 32- and 64-bit Cygwin, the pasted data could appear corrupted, + * or partially interpreted as a size which can cause an access violation. + */ + struct timespec ts; // 8 bytes on 32-bit Cygwin, 16 bytes on 64-bit Cygwin + struct + { + uint64_t cb_sec; // 8 bytes everywhere + uint64_t cb_nsec; // 8 bytes everywhere + }; + }; + uint64_t cb_size; // 8 bytes everywhere +} cygcb_t; + +#endif diff --git a/winsup/cygwin/release/3.3.0 b/winsup/cygwin/release/3.3.0 index 2df81a4ae..895c27397 100644 --- a/winsup/cygwin/release/3.3.0 +++ b/winsup/cygwin/release/3.3.0 @@ -74,3 +74,7 @@ Bug Fixes - Fix pty master closing error regarding attach_mutex. Addresses: https://cygwin.com/pipermail/cygwin-developers/2021-October/012418.html + +- Fix access violation that can sometimes occur when copy/pasting between + 32-bit and 64-bit Cygwin environments. Align clipboard descriptor layouts. + Addresses: https://cygwin.com/pipermail/cygwin-patches/2021q4/011517.html
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