[PATCH] asm-generic: io: Fix ioport_map() for !CONFIG_GENERIC_IOMAP && CONFIG_INDIRECT_PIO

[PATCH] asm-generic: io: Fix ioport_map() for !CONFIG_GENERIC_IOMAP && CONFIG_INDIRECT_PIO

[Andrew Murray]

The !CONFIG_GENERIC_IOMAP version of ioport_map uses MMIO_UPPER_LIMIT to
prevent users from making I/O accesses outside the expected I/O range -
however it erroneously treats MMIO_UPPER_LIMIT as a mask which is
contradictory to its other users.

The introduction of CONFIG_INDIRECT_PIO, which subtracts an arbitrary
amount from IO_SPACE_LIMIT to form MMIO_UPPER_LIMIT, results in ioport_map
mangling the given port rather than capping it.

We address this by aligning more closely with the CONFIG_GENERIC_IOMAP
implementation of ioport_map by using the comparison operator and
returning NULL where the port exceeds MMIO_UPPER_LIMIT. Though note that
we preserve the existing behavior of masking with IO_SPACE_LIMIT such that
we don't break existing buggy drivers that somehow rely on this masking.

Fixes: 5745392e0c2b ("PCI: Apply the new generic I/O management on PCI IO hosts")
Reported-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Andrew Murray <andrew.murray@arm.com>
---
 include/asm-generic/io.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/include/asm-generic/io.h b/include/asm-generic/io.h
index 66d1d45..d356f80 100644
--- a/include/asm-generic/io.h
+++ b/include/asm-generic/io.h
@@ -1026,7 +1026,8 @@ static inline void __iomem *ioremap_wt(phys_addr_t offset, size_t size)
 #define ioport_map ioport_map
 static inline void __iomem *ioport_map(unsigned long port, unsigned int nr)
 {
-	return PCI_IOBASE + (port & MMIO_UPPER_LIMIT);
+	port &= IO_SPACE_LIMIT;
+	return (port > MMIO_UPPER_LIMIT) ? NULL : PCI_IOBASE + port;
 }
 #endif
 
-- 
2.7.4

Re: [PATCH] asm-generic: io: Fix ioport_map() for !CONFIG_GENERIC_IOMAP && CONFIG_INDIRECT_PIO

[Will Deacon]

On Thu, Sep 13, 2018 at 01:48:27PM +0100, Andrew Murray wrote:
> The !CONFIG_GENERIC_IOMAP version of ioport_map uses MMIO_UPPER_LIMIT to
> prevent users from making I/O accesses outside the expected I/O range -
> however it erroneously treats MMIO_UPPER_LIMIT as a mask which is
> contradictory to its other users.
> 
> The introduction of CONFIG_INDIRECT_PIO, which subtracts an arbitrary
> amount from IO_SPACE_LIMIT to form MMIO_UPPER_LIMIT, results in ioport_map
> mangling the given port rather than capping it.
> 
> We address this by aligning more closely with the CONFIG_GENERIC_IOMAP
> implementation of ioport_map by using the comparison operator and
> returning NULL where the port exceeds MMIO_UPPER_LIMIT. Though note that
> we preserve the existing behavior of masking with IO_SPACE_LIMIT such that
> we don't break existing buggy drivers that somehow rely on this masking.
> 
> Fixes: 5745392e0c2b ("PCI: Apply the new generic I/O management on PCI IO hosts")
> Reported-by: Will Deacon <will.deacon@arm.com>
> Signed-off-by: Andrew Murray <andrew.murray@arm.com>
> ---
>  include/asm-generic/io.h | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/include/asm-generic/io.h b/include/asm-generic/io.h
> index 66d1d45..d356f80 100644
> --- a/include/asm-generic/io.h
> +++ b/include/asm-generic/io.h
> @@ -1026,7 +1026,8 @@ static inline void __iomem *ioremap_wt(phys_addr_t offset, size_t size)
>  #define ioport_map ioport_map
>  static inline void __iomem *ioport_map(unsigned long port, unsigned int nr)
>  {
> -	return PCI_IOBASE + (port & MMIO_UPPER_LIMIT);
> +	port &= IO_SPACE_LIMIT;
> +	return (port > MMIO_UPPER_LIMIT) ? NULL : PCI_IOBASE + port;
>  }
>  #endif

Thanks, that fixes legacy virtio PCI devices under kvmtool, so:

Tested-by: Will Deacon <will.deacon@arm.com>

Will

Re: [PATCH] asm-generic: io: Fix ioport_map() for !CONFIG_GENERIC_IOMAP && CONFIG_INDIRECT_PIO

[Arnd Bergmann]

On Thu, Sep 13, 2018 at 2:48 PM Andrew Murray <andrew.murray@arm.com> wrote:
>
> The !CONFIG_GENERIC_IOMAP version of ioport_map uses MMIO_UPPER_LIMIT to
> prevent users from making I/O accesses outside the expected I/O range -
> however it erroneously treats MMIO_UPPER_LIMIT as a mask which is
> contradictory to its other users.
>
> The introduction of CONFIG_INDIRECT_PIO, which subtracts an arbitrary
> amount from IO_SPACE_LIMIT to form MMIO_UPPER_LIMIT, results in ioport_map
> mangling the given port rather than capping it.
>
> We address this by aligning more closely with the CONFIG_GENERIC_IOMAP
> implementation of ioport_map by using the comparison operator and
> returning NULL where the port exceeds MMIO_UPPER_LIMIT. Though note that
> we preserve the existing behavior of masking with IO_SPACE_LIMIT such that
> we don't break existing buggy drivers that somehow rely on this masking.
>
> Fixes: 5745392e0c2b ("PCI: Apply the new generic I/O management on PCI IO hosts")
> Reported-by: Will Deacon <will.deacon@arm.com>
> Signed-off-by: Andrew Murray <andrew.murray@arm.com>

Looks good to me,
Reviewed-by: Arnd Bergmann <arnd@arndb.de>

Can you take this through the arm64 tree?

Re: [PATCH] asm-generic: io: Fix ioport_map() for !CONFIG_GENERIC_IOMAP && CONFIG_INDIRECT_PIO

[Will Deacon]

On Thu, Sep 13, 2018 at 04:00:54PM +0200, Arnd Bergmann wrote:
> On Thu, Sep 13, 2018 at 2:48 PM Andrew Murray <andrew.murray@arm.com> wrote:
> >
> > The !CONFIG_GENERIC_IOMAP version of ioport_map uses MMIO_UPPER_LIMIT to
> > prevent users from making I/O accesses outside the expected I/O range -
> > however it erroneously treats MMIO_UPPER_LIMIT as a mask which is
> > contradictory to its other users.
> >
> > The introduction of CONFIG_INDIRECT_PIO, which subtracts an arbitrary
> > amount from IO_SPACE_LIMIT to form MMIO_UPPER_LIMIT, results in ioport_map
> > mangling the given port rather than capping it.
> >
> > We address this by aligning more closely with the CONFIG_GENERIC_IOMAP
> > implementation of ioport_map by using the comparison operator and
> > returning NULL where the port exceeds MMIO_UPPER_LIMIT. Though note that
> > we preserve the existing behavior of masking with IO_SPACE_LIMIT such that
> > we don't break existing buggy drivers that somehow rely on this masking.
> >
> > Fixes: 5745392e0c2b ("PCI: Apply the new generic I/O management on PCI IO hosts")
> > Reported-by: Will Deacon <will.deacon@arm.com>
> > Signed-off-by: Andrew Murray <andrew.murray@arm.com>
> 
> Looks good to me,
> Reviewed-by: Arnd Bergmann <arnd@arndb.de>
> 
> Can you take this through the arm64 tree?

Yup, I'll queue it up as a fix.

Cheers,

Will

Re: [PATCH] asm-generic: io: Fix ioport_map() for !CONFIG_GENERIC_IOMAP && CONFIG_INDIRECT_PIO

[John Garry]

- dead e-mail addresses (Zhichang, Gabriele)

On 13/09/2018 13:48, Andrew Murray wrote:

Hi Andrew,

> The !CONFIG_GENERIC_IOMAP version of ioport_map uses MMIO_UPPER_LIMIT to
> prevent users from making I/O accesses outside the expected I/O range -
> however it erroneously treats MMIO_UPPER_LIMIT as a mask which is
> contradictory to its other users.
>
> The introduction of CONFIG_INDIRECT_PIO, which subtracts an arbitrary
> amount from IO_SPACE_LIMIT to form MMIO_UPPER_LIMIT, results in ioport_map
> mangling the given port rather than capping it.
>
> We address this by aligning more closely with the CONFIG_GENERIC_IOMAP
> implementation of ioport_map by using the comparison operator and
> returning NULL where the port exceeds MMIO_UPPER_LIMIT. Though note that
> we preserve the existing behavior of masking with IO_SPACE_LIMIT such that
> we don't break existing buggy drivers that somehow rely on this masking.

I wouldn't say any drivers rely on this - for the only device driver 
which uses the "Indirect" IO space region above MMIO_UPPER_LIMIT 
(HiSilicon LPC), no child device driver for that host uses ioport_map() 
[those being ipmi si and 8250 generic+of drivers].

Regardless of that, it seems better to return NULL when the port is 
out-of-range, rather than masking it.

Cheers

>
> Fixes: 5745392e0c2b ("PCI: Apply the new generic I/O management on PCI IO hosts")
> Reported-by: Will Deacon <will.deacon@arm.com>
> Signed-off-by: Andrew Murray <andrew.murray@arm.com>

Reviewed-by: John Garry <john.garry@huawei.com>

> ---
>  include/asm-generic/io.h | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/include/asm-generic/io.h b/include/asm-generic/io.h
> index 66d1d45..d356f80 100644
> --- a/include/asm-generic/io.h
> +++ b/include/asm-generic/io.h
> @@ -1026,7 +1026,8 @@ static inline void __iomem *ioremap_wt(phys_addr_t offset, size_t size)
>  #define ioport_map ioport_map
>  static inline void __iomem *ioport_map(unsigned long port, unsigned int nr)
>  {
> -	return PCI_IOBASE + (port & MMIO_UPPER_LIMIT);
> +	port &= IO_SPACE_LIMIT;
> +	return (port > MMIO_UPPER_LIMIT) ? NULL : PCI_IOBASE + port;
>  }
>  #endif
>
>

Re: [PATCH] asm-generic: io: Fix ioport_map() for !CONFIG_GENERIC_IOMAP && CONFIG_INDIRECT_PIO

[Andrew Murray]

On Mon, Sep 17, 2018 at 03:42:32PM +0100, John Garry wrote:
> - dead e-mail addresses (Zhichang, Gabriele)
> 
> On 13/09/2018 13:48, Andrew Murray wrote:
> 
> Hi Andrew,
> 
> > The !CONFIG_GENERIC_IOMAP version of ioport_map uses MMIO_UPPER_LIMIT to
> > prevent users from making I/O accesses outside the expected I/O range -
> > however it erroneously treats MMIO_UPPER_LIMIT as a mask which is
> > contradictory to its other users.
> > 
> > The introduction of CONFIG_INDIRECT_PIO, which subtracts an arbitrary
> > amount from IO_SPACE_LIMIT to form MMIO_UPPER_LIMIT, results in ioport_map
> > mangling the given port rather than capping it.
> > 
> > We address this by aligning more closely with the CONFIG_GENERIC_IOMAP
> > implementation of ioport_map by using the comparison operator and
> > returning NULL where the port exceeds MMIO_UPPER_LIMIT. Though note that
> > we preserve the existing behavior of masking with IO_SPACE_LIMIT such that
> > we don't break existing buggy drivers that somehow rely on this masking.
> 
> I wouldn't say any drivers rely on this - for the only device driver which
> uses the "Indirect" IO space region above MMIO_UPPER_LIMIT (HiSilicon LPC),
> no child device driver for that host uses ioport_map() [those being ipmi si
> and 8250 generic+of drivers].

I was really referring to the existing !CONFIG_GENERIC_IOMAP && 
!CONFIG_INDIRECT_PIO use cases where there may be drivers (however unlikely)
that provide ioport_map an incorrect address which, due to the masking, gets
converted into a valid address. Returning NULL for these would result in new
run-time errors therefore it seemed safer to change this to support the new
"indirect IO" whilst not breaking existing bad drivers.

A more correct implementation would always return NULL if
port > IO_SPACE_LIMIT - it would fully align it with the CONFIG_GENERIC_IOMAP
implementation - in my view these two implementations should behave the same
with respect to error handling - at the moment they don't.


> 
> Regardless of that, it seems better to return NULL when the port is
> out-of-range, rather than masking it.
> 
> Cheers
> 
> > 
> > Fixes: 5745392e0c2b ("PCI: Apply the new generic I/O management on PCI IO hosts")
> > Reported-by: Will Deacon <will.deacon@arm.com>
> > Signed-off-by: Andrew Murray <andrew.murray@arm.com>
> 
> Reviewed-by: John Garry <john.garry@huawei.com>

Thanks for the review.

Andrew Murray

> 
> > ---
> >  include/asm-generic/io.h | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> > 
> > diff --git a/include/asm-generic/io.h b/include/asm-generic/io.h
> > index 66d1d45..d356f80 100644
> > --- a/include/asm-generic/io.h
> > +++ b/include/asm-generic/io.h
> > @@ -1026,7 +1026,8 @@ static inline void __iomem *ioremap_wt(phys_addr_t offset, size_t size)
> >  #define ioport_map ioport_map
> >  static inline void __iomem *ioport_map(unsigned long port, unsigned int nr)
> >  {
> > -	return PCI_IOBASE + (port & MMIO_UPPER_LIMIT);
> > +	port &= IO_SPACE_LIMIT;
> > +	return (port > MMIO_UPPER_LIMIT) ? NULL : PCI_IOBASE + port;
> >  }
> >  #endif
> > 
> > 
> 
>