Re: [Xen-devel] [PATCH v5 6/8] xen/arm: introduce GNTTABOP_cache_flush

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 16.10.14 at 12:55, <stefano.stabellini@xxxxxxxxxxxxx> wrote:
> On Tue, 14 Oct 2014, Jan Beulich wrote:
>> >>> On 13.10.14 at 16:58, <stefano.stabellini@xxxxxxxxxxxxx> wrote:
>> > +static bool_t grant_map_exists(const struct domain *ld,
>> > +                        struct grant_table *rgt,
>> > +                        unsigned long mfn)
>> > +{
>> > +    const struct active_grant_entry *act;
>> > +    grant_ref_t ref;
>> > +
>> > +    ASSERT(spin_is_locked(&rgt->lock));
>> > +
>> > +    for ( ref = 0; ref != nr_grant_entries(rgt); ref++ )
>> 
>> Unless I overlooked something here or in an earlier patch I think
>> you're _still_ not enforcing a suitably low upper limit on the
>> variable that controls the maximum iteration count here. Whether
>> you enforce this the hard way (by just capping an eventual
>> command line specified value) or the soft way (by issuing a
>> warning that such a setting may hamper security, plus
>> documenting the supported value range) is up to you.
> 
> What value range do you suggest?

Whatever is suitable to limit the loop to no more than a few thousand
iterations.

Jan


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