Re: [PATCH] hw/block/nvme: slba equal to nsze is out of bounds if nlb is 1-based

[Klaus Jensen]

On Apr  9 21:31, Minwoo Im wrote:
> On 21-04-09 13:55:01, Klaus Jensen wrote:
> > On Apr  9 20:05, Minwoo Im wrote:
> > > On 21-04-09 13:14:02, Gollu Appalanaidu wrote:
> > > > NSZE is the total size of the namespace in logical blocks. So the max
> > > > addressable logical block is NLB minus 1. So your starting logical
> > > > block is equal to NSZE it is a out of range.
> > > >
> > > > Signed-off-by: Gollu Appalanaidu <anaidu.gollu@samsung.com>
> > > > ---
> > > >  hw/block/nvme.c | 2 +-
> > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > >
> > > > diff --git a/hw/block/nvme.c b/hw/block/nvme.c
> > > > index 953ec64729..be9edb1158 100644
> > > > --- a/hw/block/nvme.c
> > > > +++ b/hw/block/nvme.c
> > > > @@ -2527,7 +2527,7 @@ static uint16_t nvme_dsm(NvmeCtrl *n, NvmeRequest 
> > *req)
> > > >              uint64_t slba = le64_to_cpu(range[i].slba);
> > > >              uint32_t nlb = le32_to_cpu(range[i].nlb);
> > > >
> > > > -            if (nvme_check_bounds(ns, slba, nlb)) {
> > > > +            if (nvme_check_bounds(ns, slba, nlb) || slba == 
> > ns->id_ns.nsze) {
> > >
> > > This patch also looks like check the boundary about slba.  Should it be
> > > also checked inside of nvme_check_bounds() ?
> >
> > The catch here is that DSM is like the only command where the number of
> > logical blocks is a 1s-based value. Otherwise we always have nlb > 0, which
> > means that nvme_check_bounds() will always "do the right thing".
> >
> > My main gripe here is that (in my mind), by definition, a "zero length
> > range" does not reference any LBAs at all. So how can it result in LBA Out
> > of Range?
>
> Even if this is not the LBA out of range case which is currently what
> nvme_check_bounds() checking, but I thought the function checks the
> bounds so that we can add one more check inside of that function like:
> (If SLBA is 0-based or not, slba should not be nsze, isn't it ?)
>
> diff --git a/hw/block/nvme.c b/hw/block/nvme.c
> index 7244534a89e9..25a7db5ecbd8 100644
> --- a/hw/block/nvme.c
> +++ b/hw/block/nvme.c
> @@ -1415,6 +1415,10 @@ static inline uint16_t nvme_check_bounds(NvmeNamespace 
> *ns, uint64_t slba,
> {
>     uint64_t nsze = le64_to_cpu(ns->id_ns.nsze);
>
> +    if (slba == nsze) {
> +        return NVME_INVALID_FIELD | NVME_DNR;
> +    }
> +
>     if (unlikely(UINT64_MAX - slba < nlb || slba + nlb > nsze)) {
>         return NVME_LBA_RANGE | NVME_DNR;
>     }
>
> Or am I missing something here ;) ?

No, not at all, it's just that this additional check is never needed for 
any other command than DSM since, as far as I remember, DSM is the only 
command with the 1s-based NLB value fuckup.

This means that nlb will always be at least 1, so slba + 1 > nsze will 
be false if slba == nsze.

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