Re: [PATCH v2 7/9] vdpa: solidrun: Fix potential UB bug with devres

Philipp Stanner
2024-08-21T12:26:06Z

On Wed, 2024-08-21 at 08:12 -0400, Michael S. Tsirkin wrote:
> On Wed, Aug 21, 2024 at 09:18:40AM +0200, Philipp Stanner wrote:
> > In psnet_open_pf_bar() a string later passed to
> > pcim_iomap_regions() is
> > placed on the stack. Neither pcim_iomap_regions() nor the functions
> > it
> > calls copy that string.
> >
> > Should the string later ever be used, this, consequently, causes
> > undefined behavior since the stack frame will by then have
> > disappeared.
> >
> > Fix the bug by allocating the string on the heap through
> > devm_kasprintf().
> >
> > Cc: stable@vger.kernel.org # v6.3
> > Fixes: 51a8f9d7f587 ("virtio: vdpa: new SolidNET DPU driver.")
> > Reported-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
> > Closes:
> > https://lore.kernel.org/all/74e9109a-ac59-49e2-9b1d-d825c9c9f891@wanadoo.fr/
> > Suggested-by: Andy Shevchenko <andy@kernel.org>
> > Signed-off-by: Philipp Stanner <pstanner@redhat.com>
>
> I don't get why is this a part of a cleanup series -
> looks like an unrelated bugfix?

It was discovered in the discussion of v1 of this series.

It indeed is an unrelated bugfix and could be merged separately. But my
patch #8 depends on it.

So it would be convenient to merge it into mainline through this
series, and have stable just pick patch #7.

Or should it be done differently, in your opinion?

P.

>
>
> > ---
> >  drivers/vdpa/solidrun/snet_main.c | 7 +++++--
> >  1 file changed, 5 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/vdpa/solidrun/snet_main.c
> > b/drivers/vdpa/solidrun/snet_main.c
> > index 99428a04068d..4d42a05d70fc 100644
> > --- a/drivers/vdpa/solidrun/snet_main.c
> > +++ b/drivers/vdpa/solidrun/snet_main.c
> > @@ -555,7 +555,7 @@ static const struct vdpa_config_ops
> > snet_config_ops = {
> >
> >  static int psnet_open_pf_bar(struct pci_dev *pdev, struct psnet
> > *psnet)
> >  {
> > - char name[50];
> > + char *name;
> >   int ret, i, mask = 0;
> >   /* We don't know which BAR will be used to communicate..
> >   * We will map every bar with len > 0.
> > @@ -573,7 +573,10 @@ static int psnet_open_pf_bar(struct pci_dev
> > *pdev, struct psnet *psnet)
> >   return -ENODEV;
> >   }
> >
> > - snprintf(name, sizeof(name), "psnet[%s]-bars",
> > pci_name(pdev));
> > + name = devm_kasprintf(&pdev->dev, GFP_KERNEL, "psnet[%s]-
> > bars", pci_name(pdev));
> > + if (!name)
> > + return -ENOMEM;
> > +
> >   ret = pcim_iomap_regions(pdev, mask, name);
> >   if (ret) {
> >   SNET_ERR(pdev, "Failed to request and map PCI
> > BARs\n");
> > --
> > 2.46.0
>