2021-04-29 11:04:16

by Colin King

Subject: [PATCH][next] PCI: mediatek-gen3: Add missing null pointer check

From: Colin Ian King <[email protected]>

The call to platform_get_resource_byname can potentially return null, so
add a null pointer check to avoid a null pointer dereference issue.

Addresses-Coverity: ("Dereference null return")
Fixes: 441903d9e8f0 ("PCI: mediatek-gen3: Add MediaTek Gen3 driver for MT8192")
Signed-off-by: Colin Ian King <[email protected]>
---
drivers/pci/controller/pcie-mediatek-gen3.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/drivers/pci/controller/pcie-mediatek-gen3.c b/drivers/pci/controller/pcie-mediatek-gen3.c
index 20165e4a75b2..3c5b97716d40 100644
--- a/drivers/pci/controller/pcie-mediatek-gen3.c
+++ b/drivers/pci/controller/pcie-mediatek-gen3.c
@@ -721,6 +721,8 @@ static int mtk_pcie_parse_port(struct mtk_pcie_port *port)
int ret;

regs = platform_get_resource_byname(pdev, IORESOURCE_MEM, "pcie-mac");
+ if (!regs)
+ return -EINVAL;
port->base = devm_ioremap_resource(dev, regs);
if (IS_ERR(port->base)) {
dev_err(dev, "failed to map register base\n");
--
2.30.2

2021-04-30 07:25:51

by Jianjun Wang (王建军)

Subject: Re: [PATCH][next] PCI: mediatek-gen3: Add missing null pointer check

Hi Colin,

On Thu, 2021-04-29 at 12:00 +0100, Colin King wrote:
> From: Colin Ian King <[email protected]>
>
> The call to platform_get_resource_byname can potentially return null, so
> add a null pointer check to avoid a null pointer dereference issue.
>
> Addresses-Coverity: ("Dereference null return")
> Fixes: 441903d9e8f0 ("PCI: mediatek-gen3: Add MediaTek Gen3 driver for MT8192")
> Signed-off-by: Colin Ian King <[email protected]>
> ---
> drivers/pci/controller/pcie-mediatek-gen3.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/drivers/pci/controller/pcie-mediatek-gen3.c b/drivers/pci/controller/pcie-mediatek-gen3.c
> index 20165e4a75b2..3c5b97716d40 100644
> --- a/drivers/pci/controller/pcie-mediatek-gen3.c
> +++ b/drivers/pci/controller/pcie-mediatek-gen3.c
> @@ -721,6 +721,8 @@ static int mtk_pcie_parse_port(struct mtk_pcie_port *port)
> int ret;
>
> regs = platform_get_resource_byname(pdev, IORESOURCE_MEM, "pcie-mac");
> + if (!regs)
> + return -EINVAL;

Thanks for your patch.

devm_ioremap_resource() will check and decode this null pointer
dereference error, so I don't think we need to check here.

Thanks.

> port->base = devm_ioremap_resource(dev, regs);
> if (IS_ERR(port->base)) {
> dev_err(dev, "failed to map register base\n");

2021-04-30 07:49:35

by Christophe JAILLET

Subject: Re: [PATCH][next] PCI: mediatek-gen3: Add missing null pointer check

Le 29/04/2021 à 13:00, Colin King a écrit :
> From: Colin Ian King <[email protected]>
>
> The call to platform_get_resource_byname can potentially return null, so
> add a null pointer check to avoid a null pointer dereference issue.
>
> Addresses-Coverity: ("Dereference null return")
> Fixes: 441903d9e8f0 ("PCI: mediatek-gen3: Add MediaTek Gen3 driver for MT8192")
> Signed-off-by: Colin Ian King <[email protected]>
> ---
> drivers/pci/controller/pcie-mediatek-gen3.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/drivers/pci/controller/pcie-mediatek-gen3.c b/drivers/pci/controller/pcie-mediatek-gen3.c
> index 20165e4a75b2..3c5b97716d40 100644
> --- a/drivers/pci/controller/pcie-mediatek-gen3.c
> +++ b/drivers/pci/controller/pcie-mediatek-gen3.c
> @@ -721,6 +721,8 @@ static int mtk_pcie_parse_port(struct mtk_pcie_port *port)
> int ret;
>
> regs = platform_get_resource_byname(pdev, IORESOURCE_MEM, "pcie-mac");
> + if (!regs)
> + return -EINVAL;
> port->base = devm_ioremap_resource(dev, regs);
> if (IS_ERR(port->base)) {
> dev_err(dev, "failed to map register base\n");
>

Nitpick:
Using 'devm_platform_ioremap_resource_byname' is slightly less
verbose and should please Coverity.


Also, which git repo are you using? On linux-next ([1)], your proposed
patch is already part of "PCI: mediatek-gen3: Add MediaTek Gen3 driver
for MT8192".

[1]:
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/log/drivers/pci/controller/pcie-mediatek-gen3.c

CJ

2021-04-30 08:42:56

by Lorenzo Pieralisi

Subject: Re: [PATCH][next] PCI: mediatek-gen3: Add missing null pointer check

On Thu, Apr 29, 2021 at 12:00:40PM +0100, Colin King wrote:
> From: Colin Ian King <[email protected]>
>
> The call to platform_get_resource_byname can potentially return null, so
> add a null pointer check to avoid a null pointer dereference issue.
>
> Addresses-Coverity: ("Dereference null return")
> Fixes: 441903d9e8f0 ("PCI: mediatek-gen3: Add MediaTek Gen3 driver for MT8192")
> Signed-off-by: Colin Ian King <[email protected]>
> ---
> drivers/pci/controller/pcie-mediatek-gen3.c | 2 ++
> 1 file changed, 2 insertions(+)

Squashed into the commit it is fixing, in my pci/mediatek branch.

Thanks,
Lorenzo

> diff --git a/drivers/pci/controller/pcie-mediatek-gen3.c b/drivers/pci/controller/pcie-mediatek-gen3.c
> index 20165e4a75b2..3c5b97716d40 100644
> --- a/drivers/pci/controller/pcie-mediatek-gen3.c
> +++ b/drivers/pci/controller/pcie-mediatek-gen3.c
> @@ -721,6 +721,8 @@ static int mtk_pcie_parse_port(struct mtk_pcie_port *port)
> int ret;
>
> regs = platform_get_resource_byname(pdev, IORESOURCE_MEM, "pcie-mac");
> + if (!regs)
> + return -EINVAL;
> port->base = devm_ioremap_resource(dev, regs);
> if (IS_ERR(port->base)) {
> dev_err(dev, "failed to map register base\n");
> --
> 2.30.2
>

2021-04-30 16:36:16

by Bjorn Helgaas

Subject: Re: [PATCH][next] PCI: mediatek-gen3: Add missing null pointer check

On Fri, Apr 30, 2021 at 09:47:06AM +0200, Christophe JAILLET wrote:
> Le 29/04/2021 ? 13:00, Colin King a ?crit?:
> > From: Colin Ian King <[email protected]>
> >
> > The call to platform_get_resource_byname can potentially return null, so
> > add a null pointer check to avoid a null pointer dereference issue.
> >
> > Addresses-Coverity: ("Dereference null return")
> > Fixes: 441903d9e8f0 ("PCI: mediatek-gen3: Add MediaTek Gen3 driver for MT8192")
> > Signed-off-by: Colin Ian King <[email protected]>
> > ---
> > drivers/pci/controller/pcie-mediatek-gen3.c | 2 ++
> > 1 file changed, 2 insertions(+)
> >
> > diff --git a/drivers/pci/controller/pcie-mediatek-gen3.c b/drivers/pci/controller/pcie-mediatek-gen3.c
> > index 20165e4a75b2..3c5b97716d40 100644
> > --- a/drivers/pci/controller/pcie-mediatek-gen3.c
> > +++ b/drivers/pci/controller/pcie-mediatek-gen3.c
> > @@ -721,6 +721,8 @@ static int mtk_pcie_parse_port(struct mtk_pcie_port *port)
> > int ret;
> > regs = platform_get_resource_byname(pdev, IORESOURCE_MEM, "pcie-mac");
> > + if (!regs)
> > + return -EINVAL;
> > port->base = devm_ioremap_resource(dev, regs);
> > if (IS_ERR(port->base)) {
> > dev_err(dev, "failed to map register base\n");
> >
>
> Nitpick:
> Using 'devm_platform_ioremap_resource_byname' is slightly less verbose
> and should please Coverity.

Not a nitpick at all. Jianjun is correct that devm_ioremap_resource()
does check "regs" for NULL and it fails gracefully before trying to
dereference it, so the extra check shouldn't be needed. And most
cases in drivers/pci/ look like this, without the extra check:

res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "app");
base = devm_ioremap_resource(dev, res);
if (IS_ERR(base))
...

If devm_platform_ioremap_resource_byname() keeps Coverity happy, I
think that's what we should be doing across drivers/pci/. Coverity
false positives are a hassle.

Seems like something for next cycle since we're in the middle of the
merge window.

> Also, which git repo are you using? On linux-next ([1)], your proposed patch
> is already part of "PCI: mediatek-gen3: Add MediaTek Gen3 driver for
> MT8192".
>
> [1]: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/log/drivers/pci/controller/pcie-mediatek-gen3.c

I think this is because Lorenzo already squashed Colin's change in.

Bjorn

2021-05-03 07:06:22

by Dan Carpenter

Subject: Re: [PATCH][next] PCI: mediatek-gen3: Add missing null pointer check

On Fri, Apr 30, 2021 at 11:34:50AM -0500, Bjorn Helgaas wrote:
> On Fri, Apr 30, 2021 at 09:47:06AM +0200, Christophe JAILLET wrote:
> > Le 29/04/2021 ? 13:00, Colin King a ?crit?:
> > > From: Colin Ian King <[email protected]>
> > >
> > > The call to platform_get_resource_byname can potentially return null, so
> > > add a null pointer check to avoid a null pointer dereference issue.
> > >
> > > Addresses-Coverity: ("Dereference null return")
> > > Fixes: 441903d9e8f0 ("PCI: mediatek-gen3: Add MediaTek Gen3 driver for MT8192")
> > > Signed-off-by: Colin Ian King <[email protected]>
> > > ---
> > > drivers/pci/controller/pcie-mediatek-gen3.c | 2 ++
> > > 1 file changed, 2 insertions(+)
> > >
> > > diff --git a/drivers/pci/controller/pcie-mediatek-gen3.c b/drivers/pci/controller/pcie-mediatek-gen3.c
> > > index 20165e4a75b2..3c5b97716d40 100644
> > > --- a/drivers/pci/controller/pcie-mediatek-gen3.c
> > > +++ b/drivers/pci/controller/pcie-mediatek-gen3.c
> > > @@ -721,6 +721,8 @@ static int mtk_pcie_parse_port(struct mtk_pcie_port *port)
> > > int ret;
> > > regs = platform_get_resource_byname(pdev, IORESOURCE_MEM, "pcie-mac");
> > > + if (!regs)
> > > + return -EINVAL;
> > > port->base = devm_ioremap_resource(dev, regs);
> > > if (IS_ERR(port->base)) {
> > > dev_err(dev, "failed to map register base\n");
> > >
> >
> > Nitpick:
> > Using 'devm_platform_ioremap_resource_byname' is slightly less verbose
> > and should please Coverity.
>
> Not a nitpick at all. Jianjun is correct that devm_ioremap_resource()
> does check "regs" for NULL and it fails gracefully before trying to
> dereference it, so the extra check shouldn't be needed. And most
> cases in drivers/pci/ look like this, without the extra check:
>
> res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "app");
> base = devm_ioremap_resource(dev, res);
> if (IS_ERR(base))
> ...
>
> If devm_platform_ioremap_resource_byname() keeps Coverity happy, I
> think that's what we should be doing across drivers/pci/. Coverity
> false positives are a hassle.

Smatch knows that devm_ioremap_resource() will return ERR_PTR(-EINVAL)
when we pass it a NULL. ;)

regards,
dan carpenter