Re: [Qemu-devel] [PATCH] linux-user: fix host_to_target_cmsg in case of multiple headers

[Peter Maydell]

On 29 August 2015 at 17:04, Jonathan Neuschäfer <address@hidden> wrote:
> On Thu, Aug 27, 2015 at 07:06:24PM +0100, Peter Maydell wrote:
>> This definitely looks like a bug, but I don't think this is
>> a sufficient fix, because if DEBUG_REMAP is defined then the
>> locked-memory which the target_cmsghdr* is in is not a
>> simple g2h() away from the host pointer.
>>
>> What you need to do is change target_to_host_cmsg and
>> host_to_target_cmsg so that when at the top of the function
>> we do:
>>     target_cmsg_addr = tswapal(target_msgh->msg_control);
>>     target_cmsg = lock_user(VERIFY_READ, target_cmsg_addr, msg_controllen, 
>> 1);
>
> After following your advice, I found two more bugs in related code,
> which I had to fix. I probably missed something, but my test case
> (wine), which receives two headers via a single recvmsg call, is now
> working properly. Perhaps an isolated test case would be nice.

I generally test linux-user with the LTP tests:
http://wiki.qemu.org/Testing/LTP
though they're not always as good at flushing out QEMU
bugs as you might hope. Still, LTP is probably the best
home for syscall tests.

thanks
-- PMM