diff options
| author | Ken Brown <kbrown@cornell.edu> | 2020-07-20 15:59:09 +0300 |
|---|---|---|
| committer | Ken Brown <kbrown@cornell.edu> | 2020-07-20 18:56:29 +0300 |
| commit | d8a8d2ce5953af3383aff019596bdf7f7aef6c41 (patch) | |
| tree | 589eb5fef2e6e54942b16879947284bf26efe0bf /winsup | |
| parent | e0a53d66256ba720fa3ad9f4eaef94da1df11463 (diff) | |
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.
Diffstat (limited to 'winsup')
| -rw-r--r-- | winsup/cygwin/mmap.cc | 1 |
1 files changed, 1 insertions, 0 deletions
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 ()); |