Re: [PATCH] PCI: endpoint: pci-epf-vntb: Use array_index_nospec() on mws_size[] access

On Tue, Feb 17, 2026 at 07:20:23PM +0530, Manivannan Sadhasivam wrote:
> On Mon, Jan 05, 2026 at 04:56:06PM +0900, Koichiro Den wrote:
> > Follow common kernel idioms for indices derived from configfs attributes
> > and suppress Smatch warnings:
> > 
> >   epf_ntb_mw1_show() warn: potential spectre issue 'ntb->mws_size' [r]
> >   epf_ntb_mw1_store() warn: potential spectre issue 'ntb->mws_size' [w]
> > 
> > Also fix the error message for out-of-range MW indices and %lld format
> > for unsigned values.
> > 
> > Reviewed-by: Frank Li <[email protected]>
> > Signed-off-by: Koichiro Den <[email protected]>
> > ---
> > Base: https://github.com/jonmason/ntb/commit/68113d260674 (ntb-next)
> > This is a spin-off patch from the following series:
> > https://lore.kernel.org/all/[email protected]/
> > 
> >  drivers/pci/endpoint/functions/pci-epf-vntb.c | 24 +++++++++++--------
> >  1 file changed, 14 insertions(+), 10 deletions(-)
> > 
> > diff --git a/drivers/pci/endpoint/functions/pci-epf-vntb.c b/drivers/pci/endpoint/functions/pci-epf-vntb.c
> > index 83e9ab10f9c4..192dd4f4de8d 100644
> > --- a/drivers/pci/endpoint/functions/pci-epf-vntb.c
> > +++ b/drivers/pci/endpoint/functions/pci-epf-vntb.c
> > @@ -876,17 +876,19 @@ static ssize_t epf_ntb_##_name##_show(struct config_item *item,		\
> >  	struct config_group *group = to_config_group(item);		\
> >  	struct epf_ntb *ntb = to_epf_ntb(group);			\
> >  	struct device *dev = &ntb->epf->dev;				\
> > -	int win_no;							\
> > +	int win_no, idx;						\
> >  									\
> >  	if (sscanf(#_name, "mw%d", &win_no) != 1)			\
> >  		return -EINVAL;						\
> >  									\
> > -	if (win_no <= 0 || win_no > ntb->num_mws) {			\
> > -		dev_err(dev, "Invalid num_nws: %d value\n", ntb->num_mws); \
> > +	idx = win_no - 1;						\
> > +	if (idx < 0 || idx >= ntb->num_mws) {				\
> > +		dev_err(dev, "MW%d out of range (num_mws=%d)\n",	\
> > +			win_no, ntb->num_mws);				\
> >  		return -EINVAL;						\
> 
> This should be -ERANGE, but in a separate patch.
> 
> >  	}								\
> > -									\
> > -	return sprintf(page, "%lld\n", ntb->mws_size[win_no - 1]);	\
> > +	idx = array_index_nospec(idx, ntb->num_mws);			\
> > +	return sprintf(page, "%llu\n", ntb->mws_size[idx]);		\
> >  }
> >  
> >  #define EPF_NTB_MW_W(_name)						\
> > @@ -896,7 +898,7 @@ static ssize_t epf_ntb_##_name##_store(struct config_item *item,	\
> >  	struct config_group *group = to_config_group(item);		\
> >  	struct epf_ntb *ntb = to_epf_ntb(group);			\
> >  	struct device *dev = &ntb->epf->dev;				\
> > -	int win_no;							\
> > +	int win_no, idx;						\
> >  	u64 val;							\
> >  	int ret;							\
> >  									\
> > @@ -907,12 +909,14 @@ static ssize_t epf_ntb_##_name##_store(struct config_item *item,	\
> >  	if (sscanf(#_name, "mw%d", &win_no) != 1)			\
> >  		return -EINVAL;						\
> >  									\
> > -	if (win_no <= 0 || win_no > ntb->num_mws) {			\
> > -		dev_err(dev, "Invalid num_nws: %d value\n", ntb->num_mws); \
> > +	idx = win_no - 1;						\
> > +	if (idx < 0 || idx >= ntb->num_mws) {				\
> > +		dev_err(dev, "MW%d out of range (num_mws=%d)\n",	\
> > +			win_no, ntb->num_mws);				\
> >  		return -EINVAL;						\
> 
> Same here.
> 
> - Mani

Thanks for the comment. I will send a separate patch for that.

Before doing so, I have a quick question regarding the routing of pci-epf-vntb
patches.

Commit e4fe2a2fc423 ("MAINTAINERS: add PCI Endpoint NTB drivers to NTB files")
places pci-epf-vntb under the NTB subsystem. However, I'm not entirely sure
which tree (NTB or PCI EP) is expected to take changes to pci-epf-vntb.

Should updates be based on the NTB tree or the PCI EP tree?
Sorry if this has already been clarified and I just overlooked it.

Best regards,
Koichiro

> 
> >  	}								\
> > -									\
> > -	ntb->mws_size[win_no - 1] = val;				\
> > +	idx = array_index_nospec(idx, ntb->num_mws);			\
> > +	ntb->mws_size[idx] = val;					\
> >  									\
> >  	return len;							\
> >  }
> > -- 
> > 2.51.0
> > 
> 
> -- 
> மணிவண்ணன் சதாசிவம்