On Sun, Jun 21, 2009 at 1:03 PM, Erich Hoover <ehoover@mines.edu> wrote:
On Sun, Jun 21, 2009 at 10:23 AM, Erich Hoover <ehoover@mines.edu> wrote:
On Sun, Jun 21, 2009 at 1:36 AM, Damjan Jovanovic <damjan.jov@gmail.com> wrote:
...
Maybe the memory is writable but not readable, and
WSARecvFrom()/recv() is reading it while memcpy() is not?�

Maybe the memory is from a DIB section which Wine lazily mprotects and
the kernel isn't raising SIGSEGV for the protection to be reapplied?
Does simply zero-filling buf before calling WSARecvFrom() help?

The memory should be a buffer from the calling application that it is using temporarily to store update data before saving it to the hard-disk.� Yes, oddly enough zero-filling the buffer before calling WSARecvFrom() also fixes the problem.

So, where exactly should I be looking to find the real problem?� As far as I can tell the memory for the buffer is being allocated immediate prior to the call and the request is for read/write access:
0009:Call KERNEL32.VirtualAlloc(01b85000,00040000,00001000,00000004) ret=79e74a2b
0009:Ret� KERNEL32.VirtualAlloc() retval=01b85000 ret=79e74a2b
0009:Call ws2_32.recv(00000380,01ba4fc1,000178d0,00000000) ret=0036a287
...

After looking over the documentation for VirtualAlloc, it appears that Wine should be zeroing the returned memory if MEM_COMMIT is specified.� Making this change (rather than playing around in the socket code) also fixes the problem (see attached patch).� Do you think this step occurs if write access isn't specified?


Erich Hoover
ehoover@mines.edu

Any thoughts on this?� Is there anything a "+relay" wouldn't catch that could occur between the call to KERNEL32.VirtualAlloc and the call to ws2_32.recv?� This behavior (the memory area having to be cleared before the recv call) seems a tad on the odd side.

Erich Hoover
ehoover@mines.edu