Re: [PATCH v6 3/5] ntoskrnl.exe: Implement volume information queries for device files.

[Zebediah Figura (she/her)]

On 2/11/21 12:19 PM, Zebediah Figura (she/her) wrote:
> On 2/11/21 12:17 PM, Erich E. Hoover wrote:
> > On Wed, Feb 10, 2021 at 9:33 PM Zebediah Figura (she/her)
> > <zfigura(a)codeweavers.com> wrote:
> > > Taking a closer look since the last time I looked at this patch...
> > > > From: "Erich E. Hoover" <erich.e.hoover(a)gmail.com>
> > > > Subject: [PATCH v6 3/5] ntoskrnl.exe: Implement volume information queries for device files.
> > > > Message-Id: <CAEU2+vqrdb5u4fTQe80yUHBciFLwoF0RmiXMsFZ_s_wbndm+jQ(a)mail.gmail.com>
> > > > Date: Sat, 6 Feb 2021 11:25:22 -0700
> > > > ...
> > > > +    if (out_size)
> > > > +    {
> > > > +        if (out_size > context->in_size)
> > > > +        {
> > > > +            if (!(out_buff = HeapAlloc( GetProcessHeap(), 0, out_size ))) return STATUS_NO_MEMORY;
> > > > +            memcpy( out_buff, context->in_buff, context->in_size );
> > > > +            to_free = context->in_buff;
> > > > +            context->in_buff = out_buff;
> > > > +        }
> > > > +        else
> > > > +            out_buff = context->in_buff;
> > > > +    }
> > > > +
> > >
> > > This looks wrong. No data is ever passed in to this IRP, so it should
> > > probably just always allocate an output buffer, like dispatch_read().
> >
> > This was copied from dispatch_ioctl under the assumption that some
> > future usage might need it, but you are right - according to the
> > documentation this IRP has no need for this.  I'll go ahead and match
> > the behavior in dispatch_read.
> > > [There's probably an argument to reusing context.in_buff already
> > > allocated in dispatch_read() and here, but we'd need to store the
> > > capacity of the buffer somewhere. This patch will never reuse it, as
> > > in_size should always be 0.]
> >
> > It looks to me like dispatch_read doesn't use context->in_buff, am I
> > missing something here?  (Looks to me like it always does a heap
> > allocation.)
>
> Sorry, that was probably confusing phrasing, I mean it was already
> allocated in __wine_ntoskrnl_main_loop(), and we could potentially use
> it in dispatch_read() and here.

And to further clarify, I doubt that should be a part of this patch or
this series, if it's even worth doing at all.
> > > > ...
> > > > +        FILE_FS_VOLUME_INFORMATION *info = irp->AssociatedIrp.SystemBuffer;
> > > > +        static WCHAR label[] = L"WineTestDriver";
> > >
> > > Missing "const"?
> >
> > Yup, sorry about that.
> > > > +        ULONG serial = 0xdeadbeef;
> > > > +
> > > > +        if (length < sizeof(FILE_FS_VOLUME_INFORMATION))
> > > > +        {
> > > > +            ret = STATUS_INFO_LENGTH_MISMATCH;
> > > > +            break;
> > > > +        }
> > > > +
> > > > +        info->VolumeCreationTime.QuadPart = 0; /* FIXME */
> > >
> > > "FIXME" seems a bit odd in a test like this, was that a copy/paste error?
> >
> > Yes, that's a copy/paste error from patch 4.
> > > > ...