On Fri, Oct 13, 2017 at 12:00:50PM +0100, Marc Zyngier wrote:
> On 13/10/17 11:52, Christoffer Dall wrote:
> > We currently allocate an entry dynamically, but we never check if the
> > allocation actually succeeded. We actually don't need a dynamic
> > allocation, because we know the maximum size of an ITS table entry, so
> > we can simply use an allocation on the stack.
> >
> > Cc: <stable@xxxxxxxxxxxxxxx>
> > Signed-off-by: Christoffer Dall <christoffer.dall@xxxxxxxxxx>
> > ---
> > virt/kvm/arm/vgic/vgic-its.c | 19 ++++++++-----------
> > 1 file changed, 8 insertions(+), 11 deletions(-)
> >
> > diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c
> > index f51c1e1..555f42f 100644
> > --- a/virt/kvm/arm/vgic/vgic-its.c
> > +++ b/virt/kvm/arm/vgic/vgic-its.c
> > @@ -176,6 +176,7 @@ static const struct vgic_its_abi its_table_abi_versions[] = {
> > };
> >
> > #define NR_ITS_ABIS ARRAY_SIZE(its_table_abi_versions)
> > +#define MAX_ENTRY_SIZE 8 /* Max Entry size across all ABI versions */
> >
> > inline const struct vgic_its_abi *vgic_its_get_abi(struct vgic_its *its)
> > {
> > @@ -1801,37 +1802,33 @@ typedef int (*entry_fn_t)(struct vgic_its *its, u32 id, void *entry,
> > static int scan_its_table(struct vgic_its *its, gpa_t base, int size, int esz,
> > int start_id, entry_fn_t fn, void *opaque)
> > {
> > - void *entry = kzalloc(esz, GFP_KERNEL);
> > struct kvm *kvm = its->dev->kvm;
> > unsigned long len = size;
> > int id = start_id;
> > gpa_t gpa = base;
> > + char entry[MAX_ENTRY_SIZE];
>
> Nit: you can drop the memset below if you initialize immediately, and
> GCC supporting dynamic arrays allows you to write this:
>
> char entry[esz] = { 0, };
>
> so that you don't have to add the MAX_ENTRY_SIZE.
>
Using a dynamic sized array is a great idea, but trying to initalize it
at the same time gives me:
error: variable-sized object may not be initialized
Is there a trick I'm unfamiliar with?
> > int ret;
> >
> > + memset(entry, 0, MAX_ENTRY_SIZE);
> > +
> > while (len > 0) {
> > int next_offset;
> > size_t byte_offset;
> >
> > ret = kvm_read_guest(kvm, gpa, entry, esz);
> > if (ret)
> > - goto out;
> > + return ret;
> >
> > next_offset = fn(its, id, entry, opaque);
> > - if (next_offset <= 0) {
> > - ret = next_offset;
> > - goto out;
> > - }
> > + if (next_offset <= 0)
> > + return next_offset;
> >
> > byte_offset = next_offset * esz;
> > id += next_offset;
> > gpa += byte_offset;
> > len -= byte_offset;
> > }
> > - ret = 1;
> > -
> > -out:
> > - kfree(entry);
> > - return ret;
> > + return 1;
> > }
> >
> > /**
> >
>
> Otherwise:
>
> Acked-by: Marc Zyngier <marc.zyngier@xxxxxxx>
>
Thanks!
-Christoffer