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SubjectRE: [PATCHv2 1/1] omap: Ptr "isr_reg" tracked as NULL was dereferenced


<<snip>>

> > >
> > > From: Evgeny Kuznetsov <ext-eugeny.kuznetsov@nokia.com>
> > >
> > > Value of "isr_reg" pointer is depend on configuration and GPIO method.
> > > Potentially it may have NULL value and it is dereferenced later
> > > in code. If pointer is NULL there is some kernel issue.
> >
> > Can you elaborate?
> "isr_reg" should not be NULL. But if it is NULL then there is kernel
> bug. And WARN_ON() used to show it.
> I did not see this bug, this is potentially may happen.
> >
> > > Warning and exit from function are added in this case.
> > > Also compilation check is added for correct architecture
> > > configuration.
> > >
> > > Signed-off-by: Evgeny Kuznetsov <EXT-Eugeny.Kuznetsov@nokia.com>
> > > ---
> > > arch/arm/plat-omap/gpio.c | 18 ++++++++++++++++++
> > > 1 files changed, 18 insertions(+), 0 deletions(-)
> > >
> > > diff --git a/arch/arm/plat-omap/gpio.c b/arch/arm/plat-omap/gpio.c
> > > index c05c653..d04913c 100644
> > > --- a/arch/arm/plat-omap/gpio.c
> > > +++ b/arch/arm/plat-omap/gpio.c
> > > @@ -1318,6 +1318,23 @@ static void gpio_irq_handler(unsigned int irq,
> > > struct irq_desc *desc)
> > > if (bank->method == METHOD_GPIO_44XX)
> > > isr_reg = bank->base + OMAP4_GPIO_IRQSTATUS0;
> > > #endif
> > > +
> > > +#if !defined(CONFIG_ARCH_OMAP1) && \
> > > + !defined(CONFIG_ARCH_OMAP15XX) && \
> > > + !defined(CONFIG_ARCH_OMAP16XX) && \
> > > + !defined(CONFIG_ARCH_OMAP730) && \
> > > + !defined(CONFIG_ARCH_OMAP850) && \
> > > + !defined(CONFIG_ARCH_OMAP2) && \
> > > + !defined(CONFIG_ARCH_OMAP3) && \
> > > + !defined(CONFIG_ARCH_OMAP4)
> > > +
> > > +#error "Incorrect arch configuration"
> >
> > This is not required. If the architecture is not one of the above
> > mentioned, gpio_irq_handler() will not be used/called at all.
> This could be removed.
>
> > Also all the possible gpio methods for a given OMAP architecture are
> > already considered with "#ifdef"s and (bank->method) checks in
> > gpio_irq_handler().
> It is not cover all cased, e.g. for OMAP4 arch:
> ....
> #if defined(CONFIG_ARCH_OMAP4)
> if (bank->method == METHOD_GPIO_44XX)
> isr_reg = bank->base + OMAP4_GPIO_IRQSTATUS0;
> #endif
> .....
>
> If (bank->method != METHOD_GPIO_44XX) then isr_reg will be NULL.
> This should not happen, but potentially may have place.

When would it fail? If it is CONFIG_ARCH_OMAP4, the gpio method can
only be METHOD_GPIO_44XX. Else if it is for some other OMAP architecture,
the gpio_method is similarly taken care. So this cannot happen.

>
> >
> > > +
> > > +#endif
> > > +
> > > + if (WARN_ON(!isr_reg))
> > > + goto exit;
> >
> > For the above mentioned reason, this isr_reg would be non-NULL. Have
> > you observed this error anytime?
> I did not see this bug, this is potentially may happen.
> >
> > Also, the omap-gpio code has similar code spread all over and has to be
> > anyway cleaned-up. Is there any reason why gpio_irq_handler() alone is
> > addressed in this patch?
> Here "isr_reg" is used later in code and may cause oops if it is NULL.
> >
> > > +
> > > while(1) {
> > > u32 isr_saved, level_mask = 0;
> > > u32 enabled;
> > > @@ -1377,6 +1394,7 @@ static void gpio_irq_handler(unsigned int irq,
> > > struct irq_desc *desc)
> > > configured, we must unmask the bank interrupt only after
> > > handler(s) are executed in order to avoid spurious bank
> > > interrupt */
> > > +exit:
> > > if (!unmasked)
> > > desc->chip->unmask(irq);
> > >
> > > --
> > > 1.6.3.3
> >
>



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