From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 2210) id 43E5B3851C39; Mon, 20 Jul 2020 16:08:00 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 43E5B3851C39 Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit From: Ken Brown To: cygwin-cvs@sourceware.org Subject: [newlib-cygwin] Cygwin: mmap: fix mapping beyond EOF on 64 bit X-Act-Checkin: newlib-cygwin X-Git-Author: Ken Brown X-Git-Refname: refs/heads/master X-Git-Oldrev: e0a53d66256ba720fa3ad9f4eaef94da1df11463 X-Git-Newrev: d8a8d2ce5953af3383aff019596bdf7f7aef6c41 Message-Id: <20200720160800.43E5B3851C39@sourceware.org> Date: Mon, 20 Jul 2020 16:08:00 +0000 (GMT) X-BeenThere: cygwin-cvs@cygwin.com X-Mailman-Version: 2.1.29 Precedence: list List-Id: Cygwin core component git logs List-Unsubscribe: , List-Archive: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 20 Jul 2020 16:08:00 -0000 https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=d8a8d2ce5953af3383aff019596bdf7f7aef6c41 commit d8a8d2ce5953af3383aff019596bdf7f7aef6c41 Author: Ken Brown Date: Mon Jul 20 08:59:09 2020 -0400 Cygwin: mmap: fix mapping beyond EOF on 64 bit Commit 605bdcd410384dda6db66b9b8cd19e863702e1bb enabled mapping beyond EOF in 64 bit environments. But the variable 'orig_len' did not get rounded up to a multiple of 64K. This rounding was done on 32 bit only. Fix this by rounding up orig_len on 64 bit, in the same place where 'len' is rounded up. Rounding up is needed to make sigbus_page_len a multiple of the allocation granularity. In addition, failing to round up could cause orig_len to be smaller than len. Since these are both unsigned values, the statement 'orig_len -= len' could then cause orig_len to be huge, and mmap would fail with errno EFBIG. I observed this failure while debugging the problem reported in https://sourceware.org/pipermail/cygwin/2020-July/245557.html. The failure can be seen by running the test case in that report under gdb or strace. Diff: --- winsup/cygwin/mmap.cc | 1 + 1 file changed, 1 insertion(+) diff --git a/winsup/cygwin/mmap.cc b/winsup/cygwin/mmap.cc index feb9e5d0e..a08d00f83 100644 --- a/winsup/cygwin/mmap.cc +++ b/winsup/cygwin/mmap.cc @@ -1144,6 +1144,7 @@ go_ahead: ends in, but there's nothing at all we can do about that. */ #ifdef __x86_64__ len = roundup2 (len, wincap.allocation_granularity ()); + orig_len = roundup2 (orig_len, wincap.allocation_granularity ()); #else len = roundup2 (len, wincap.is_wow64 () ? wincap.allocation_granularity () : wincap.page_size ());