On Sat, Jan 12, 2019 at 08:44:26AM +0300, Dan Carpenter wrote:
> On Sat, Jan 12, 2019 at 11:30:35AM +1100, Balbir Singh wrote:
> > On Wed, Jan 09, 2019 at 01:23:29PM +0300, Dan Carpenter wrote:
> > > There is a typo so we accidentally allocate enough memory for a pointer
> > > when we wanted to allocate enough for a struct.
> > >
> > > Fixes: 0bd971676e68 ("powerpc/powernv/npu: Add compound IOMMU groups")
> > > Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
> > > ---
> > > arch/powerpc/platforms/powernv/npu-dma.c | 2 +-
> > > 1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/arch/powerpc/platforms/powernv/npu-dma.c b/arch/powerpc/platforms/powernv/npu-dma.c
> > > index d7f742ed48ba..3f58c7dbd581 100644
> > > --- a/arch/powerpc/platforms/powernv/npu-dma.c
> > > +++ b/arch/powerpc/platforms/powernv/npu-dma.c
> > > @@ -564,7 +564,7 @@ struct iommu_table_group *pnv_try_setup_npu_table_group(struct pnv_ioda_pe *pe)
> > > }
> > > } else {
> > > /* Create a group for 1 GPU and attached NPUs for POWER8 */
> > > - pe->npucomp = kzalloc(sizeof(pe->npucomp), GFP_KERNEL);
> > > + pe->npucomp = kzalloc(sizeof(*pe->npucomp), GFP_KERNEL);
> >
> > To avoid these in the future, I wonder if instead of sizeof(pe->npucomp), we insist on
> > sizeof structure
> >
> > pe->npucomp = kzalloc(sizeof(struct npucomp), GFP_KERNEL);
> >
>
> The latest kernel fashion is sizeof(*ptr). It can go wrong either way.
> I don't have strong feelings about it. These sorts of bugs don't last
> long because they're caught in testing or with static analysis.
And it is easy to see someone forgot the * in "sizeof *ptr", and with
experience it will just automatically look wrong if it is forgotten; but
it isn't obvious at all if the wrong struct is used, which cannot happen
with the *ptr form, but happens frequently with the "sizeof(struct x)"
form.
Segher
