Re: [PATCH][next] powerpc/vas: Fix potential NULL pointer dereference

Gustavo A. R. Silva
2021-10-18T21:21:40Z

On Mon, Oct 18, 2021 at 02:09:31PM -0700, Tyrel Datwyler wrote:
> On 10/14/21 10:03 PM, Gustavo A. R. Silva wrote:
> > (!ptr && !ptr->foo) strikes again. :)
> >
> > The expression (!ptr && !ptr->foo) is bogus and in case ptr is NULL,
> > it leads to a NULL pointer dereference: ptr->foo.
> >
> > Fix this by converting && to ||
> >
> > This issue was detected with the help of Coccinelle, and audited and
> > fixed manually.
> >
> > Fixes: 1a0d0d5ed5e3 ("powerpc/vas: Add platform specific user window operations")
> > Cc: stable@vger.kernel.org
> > Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
> Looking at the usage pattern it is obvious that if we determine !ptr attempting
> to also confirm !ptr->ops is going to blow up.
>
> LGTM.
>
> Reviewed-by: Tyrel Datwyler <tyreld@linux.ibm.com>

Thanks, Tyrel.
--
Gustavo

>
> > ---
> > arch/powerpc/platforms/book3s/vas-api.c | 4 ++--
> > 1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/powerpc/platforms/book3s/vas-api.c b/arch/powerpc/platforms/book3s/vas-api.c
> > index 30172e52e16b..4d82c92ddd52 100644
> > --- a/arch/powerpc/platforms/book3s/vas-api.c
> > +++ b/arch/powerpc/platforms/book3s/vas-api.c
> > @@ -303,7 +303,7 @@ static int coproc_ioc_tx_win_open(struct file *fp, unsigned long arg)
> > return -EINVAL;
> > }
> >
> > - if (!cp_inst->coproc->vops && !cp_inst->coproc->vops->open_win) {
> > + if (!cp_inst->coproc->vops || !cp_inst->coproc->vops->open_win) {
> > pr_err("VAS API is not registered\n");
> > return -EACCES;
> > }
> > @@ -373,7 +373,7 @@ static int coproc_mmap(struct file *fp, struct vm_area_struct *vma)
> > return -EINVAL;
> > }
> >
> > - if (!cp_inst->coproc->vops && !cp_inst->coproc->vops->paste_addr) {
> > + if (!cp_inst->coproc->vops || !cp_inst->coproc->vops->paste_addr) {
> > pr_err("%s(): VAS API is not registered\n", __func__);
> > return -EACCES;
> > }
> >
>