Re: [Xen-devel] [PATCH 2/4] fix XENMEM_add_to_physmap preemption handling

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Wed, 2013-12-18 at 14:35 +0000, Jan Beulich wrote:
> J
>          /* Check for continuation if it's not the last interation. */
> -        if ( xatp->size > 0 && hypercall_preempt_check() )
> +        if ( xatp->size > ++done && hypercall_preempt_check() )

Hiding the loop increment inside the preemption checking is a bit subtle
(it took me a while to find it). Can't it go either before or after this
loop? With a suitable +/- 1 to the rc below if necessary.

> @@ -724,6 +731,12 @@ long do_memory_op(unsigned long cmd, XEN
>      {
>          struct xen_add_to_physmap xatp;
>  
> +        BUILD_BUG_ON((typeof(xatp.size))-1 > (UINT_MAX >> 
> MEMOP_EXTENT_SHIFT));

What does "typeof(xatp.size)-1" evaluate to? typeof can't return an int,
cant it?

> +
> +        /* Check for faked input. */

Faked as in "malicious" or faked as in "something we made up for
continuation purposes" ?



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