[PATCH v2] ARM: Fix MAX_DMA_ADDRESS overflow

[PATCH v2] ARM: Fix MAX_DMA_ADDRESS overflow

[Florian Fainelli]

Commit 26f09e9b3a06 ("mm/memblock: add memblock memory allocation apis")
added a check to determine whether arm_dma_zone_size is exceeding the
amount of kernel virtual address space available between the upper 4GB
virtual address limit and PAGE_OFFSET in order to provide a suitable
definition of MAX_DMA_ADDRESS that should fit within the 32-bit virtual
address space. The quantity used for comparison was off by a missing
trailing 0, leading to MAX_DMA_ADDRESS to be overflowing a 32-bit
quantity.

This was caught with the bcm2711 platforms which defines a dma_zone_size
of 1GB, and using a PAGE_OFFSET of 0xc000_0000 (CONFIG_VMSPLIT_3G) with
CONFIG_DEBUG_VIRTUAL enabled would lead to MAX_DMA_ADDRESS being
0x1_0000_0000 which overflows the unsigned long type used throughout
__pa() and __virt_addr_valid(). Because the virtual address passed to
__virt_addr_valid() would now be 0, the function would loudly warn, thus
making the platform unable to boot properly.

Fixes: 26f09e9b3a06 ("mm/memblock: add memblock memory allocation apis")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
---
Changes in v2:

- simplify the patch and drop the first patch that attempted to fix an
  off by one in the calculation.

 arch/arm/include/asm/dma.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm/include/asm/dma.h b/arch/arm/include/asm/dma.h
index a81dda65c576..1ffa75beb709 100644
--- a/arch/arm/include/asm/dma.h
+++ b/arch/arm/include/asm/dma.h
@@ -10,7 +10,7 @@
 #else
 #define MAX_DMA_ADDRESS	({ \
 	extern phys_addr_t arm_dma_zone_size; \
-	arm_dma_zone_size && arm_dma_zone_size < (0x10000000 - PAGE_OFFSET) ? \
+	arm_dma_zone_size && arm_dma_zone_size < (0x100000000 - PAGE_OFFSET) ? \
 		(PAGE_OFFSET + arm_dma_zone_size) : 0xffffffffUL; })
 #endif
 
-- 
2.25.1

[PATCH v2] ARM: Fix MAX_DMA_ADDRESS overflow

[Florian Fainelli]

Commit 26f09e9b3a06 ("mm/memblock: add memblock memory allocation apis")
added a check to determine whether arm_dma_zone_size is exceeding the
amount of kernel virtual address space available between the upper 4GB
virtual address limit and PAGE_OFFSET in order to provide a suitable
definition of MAX_DMA_ADDRESS that should fit within the 32-bit virtual
address space. The quantity used for comparison was off by a missing
trailing 0, leading to MAX_DMA_ADDRESS to be overflowing a 32-bit
quantity.

This was caught with the bcm2711 platforms which defines a dma_zone_size
of 1GB, and using a PAGE_OFFSET of 0xc000_0000 (CONFIG_VMSPLIT_3G) with
CONFIG_DEBUG_VIRTUAL enabled would lead to MAX_DMA_ADDRESS being
0x1_0000_0000 which overflows the unsigned long type used throughout
__pa() and __virt_addr_valid(). Because the virtual address passed to
__virt_addr_valid() would now be 0, the function would loudly warn, thus
making the platform unable to boot properly.

Fixes: 26f09e9b3a06 ("mm/memblock: add memblock memory allocation apis")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
---
Changes in v2:

- simplify the patch and drop the first patch that attempted to fix an
  off by one in the calculation.

 arch/arm/include/asm/dma.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm/include/asm/dma.h b/arch/arm/include/asm/dma.h
index a81dda65c576..1ffa75beb709 100644
--- a/arch/arm/include/asm/dma.h
+++ b/arch/arm/include/asm/dma.h
@@ -10,7 +10,7 @@
 #else
 #define MAX_DMA_ADDRESS	({ \
 	extern phys_addr_t arm_dma_zone_size; \
-	arm_dma_zone_size && arm_dma_zone_size < (0x10000000 - PAGE_OFFSET) ? \
+	arm_dma_zone_size && arm_dma_zone_size < (0x100000000 - PAGE_OFFSET) ? \
 		(PAGE_OFFSET + arm_dma_zone_size) : 0xffffffffUL; })
 #endif
 
-- 
2.25.1


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Re: [PATCH v2] ARM: Fix MAX_DMA_ADDRESS overflow

[Geert Uytterhoeven]

Hi Florian,

On Wed, Jul 6, 2022 at 6:46 PM Florian Fainelli <f.fainelli@gmail.com> wrote:
> Commit 26f09e9b3a06 ("mm/memblock: add memblock memory allocation apis")
> added a check to determine whether arm_dma_zone_size is exceeding the
> amount of kernel virtual address space available between the upper 4GB
> virtual address limit and PAGE_OFFSET in order to provide a suitable
> definition of MAX_DMA_ADDRESS that should fit within the 32-bit virtual
> address space. The quantity used for comparison was off by a missing
> trailing 0, leading to MAX_DMA_ADDRESS to be overflowing a 32-bit
> quantity.
>
> This was caught with the bcm2711 platforms which defines a dma_zone_size
> of 1GB, and using a PAGE_OFFSET of 0xc000_0000 (CONFIG_VMSPLIT_3G) with
> CONFIG_DEBUG_VIRTUAL enabled would lead to MAX_DMA_ADDRESS being
> 0x1_0000_0000 which overflows the unsigned long type used throughout
> __pa() and __virt_addr_valid(). Because the virtual address passed to
> __virt_addr_valid() would now be 0, the function would loudly warn, thus
> making the platform unable to boot properly.
>
> Fixes: 26f09e9b3a06 ("mm/memblock: add memblock memory allocation apis")
> Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
> ---
> Changes in v2:
>
> - simplify the patch and drop the first patch that attempted to fix an
>   off by one in the calculation.

Thanks for the update!

> --- a/arch/arm/include/asm/dma.h
> +++ b/arch/arm/include/asm/dma.h
> @@ -10,7 +10,7 @@
>  #else
>  #define MAX_DMA_ADDRESS        ({ \
>         extern phys_addr_t arm_dma_zone_size; \
> -       arm_dma_zone_size && arm_dma_zone_size < (0x10000000 - PAGE_OFFSET) ? \
                                                  ^^^^^^^^^^
0x10000000ULL, as the constant doesn't fit in 32-bit.
However, both gcc (9.4.0) and sparse don't seem to complain about
the missing suffix (anymore?).

> +       arm_dma_zone_size && arm_dma_zone_size < (0x100000000 - PAGE_OFFSET) ? \
>                 (PAGE_OFFSET + arm_dma_zone_size) : 0xffffffffUL; })
>  #endif

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

Re: [PATCH v2] ARM: Fix MAX_DMA_ADDRESS overflow

[Geert Uytterhoeven]

Hi Florian,

On Wed, Jul 6, 2022 at 6:46 PM Florian Fainelli <f.fainelli@gmail.com> wrote:
> Commit 26f09e9b3a06 ("mm/memblock: add memblock memory allocation apis")
> added a check to determine whether arm_dma_zone_size is exceeding the
> amount of kernel virtual address space available between the upper 4GB
> virtual address limit and PAGE_OFFSET in order to provide a suitable
> definition of MAX_DMA_ADDRESS that should fit within the 32-bit virtual
> address space. The quantity used for comparison was off by a missing
> trailing 0, leading to MAX_DMA_ADDRESS to be overflowing a 32-bit
> quantity.
>
> This was caught with the bcm2711 platforms which defines a dma_zone_size
> of 1GB, and using a PAGE_OFFSET of 0xc000_0000 (CONFIG_VMSPLIT_3G) with
> CONFIG_DEBUG_VIRTUAL enabled would lead to MAX_DMA_ADDRESS being
> 0x1_0000_0000 which overflows the unsigned long type used throughout
> __pa() and __virt_addr_valid(). Because the virtual address passed to
> __virt_addr_valid() would now be 0, the function would loudly warn, thus
> making the platform unable to boot properly.
>
> Fixes: 26f09e9b3a06 ("mm/memblock: add memblock memory allocation apis")
> Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
> ---
> Changes in v2:
>
> - simplify the patch and drop the first patch that attempted to fix an
>   off by one in the calculation.

Thanks for the update!

> --- a/arch/arm/include/asm/dma.h
> +++ b/arch/arm/include/asm/dma.h
> @@ -10,7 +10,7 @@
>  #else
>  #define MAX_DMA_ADDRESS        ({ \
>         extern phys_addr_t arm_dma_zone_size; \
> -       arm_dma_zone_size && arm_dma_zone_size < (0x10000000 - PAGE_OFFSET) ? \
                                                  ^^^^^^^^^^
0x10000000ULL, as the constant doesn't fit in 32-bit.
However, both gcc (9.4.0) and sparse don't seem to complain about
the missing suffix (anymore?).

> +       arm_dma_zone_size && arm_dma_zone_size < (0x100000000 - PAGE_OFFSET) ? \
>                 (PAGE_OFFSET + arm_dma_zone_size) : 0xffffffffUL; })
>  #endif

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

Re: [PATCH v2] ARM: Fix MAX_DMA_ADDRESS overflow

[Geert Uytterhoeven]

On Wed, Jul 6, 2022 at 9:44 PM Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> On Wed, Jul 6, 2022 at 6:46 PM Florian Fainelli <f.fainelli@gmail.com> wrote:
> > Commit 26f09e9b3a06 ("mm/memblock: add memblock memory allocation apis")
> > added a check to determine whether arm_dma_zone_size is exceeding the
> > amount of kernel virtual address space available between the upper 4GB
> > virtual address limit and PAGE_OFFSET in order to provide a suitable
> > definition of MAX_DMA_ADDRESS that should fit within the 32-bit virtual
> > address space. The quantity used for comparison was off by a missing
> > trailing 0, leading to MAX_DMA_ADDRESS to be overflowing a 32-bit
> > quantity.
> >
> > This was caught with the bcm2711 platforms which defines a dma_zone_size
> > of 1GB, and using a PAGE_OFFSET of 0xc000_0000 (CONFIG_VMSPLIT_3G) with
> > CONFIG_DEBUG_VIRTUAL enabled would lead to MAX_DMA_ADDRESS being
> > 0x1_0000_0000 which overflows the unsigned long type used throughout
> > __pa() and __virt_addr_valid(). Because the virtual address passed to
> > __virt_addr_valid() would now be 0, the function would loudly warn, thus
> > making the platform unable to boot properly.
> >
> > Fixes: 26f09e9b3a06 ("mm/memblock: add memblock memory allocation apis")
> > Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
> > ---
> > Changes in v2:
> >
> > - simplify the patch and drop the first patch that attempted to fix an
> >   off by one in the calculation.
>
> Thanks for the update!
>
> > --- a/arch/arm/include/asm/dma.h
> > +++ b/arch/arm/include/asm/dma.h
> > @@ -10,7 +10,7 @@
> >  #else
> >  #define MAX_DMA_ADDRESS        ({ \
> >         extern phys_addr_t arm_dma_zone_size; \
> > -       arm_dma_zone_size && arm_dma_zone_size < (0x10000000 - PAGE_OFFSET) ? \
>                                                   ^^^^^^^^^^
> 0x10000000ULL, as the constant doesn't fit in 32-bit.
> However, both gcc (9.4.0) and sparse don't seem to complain about
> the missing suffix (anymore?).
>
> > +       arm_dma_zone_size && arm_dma_zone_size < (0x100000000 - PAGE_OFFSET) ? \

Obviously my comment applies to the _new_ line, not to the removed
line...

> >                 (PAGE_OFFSET + arm_dma_zone_size) : 0xffffffffUL; })
> >  #endif

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

Re: [PATCH v2] ARM: Fix MAX_DMA_ADDRESS overflow

[Geert Uytterhoeven]

On Wed, Jul 6, 2022 at 9:44 PM Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> On Wed, Jul 6, 2022 at 6:46 PM Florian Fainelli <f.fainelli@gmail.com> wrote:
> > Commit 26f09e9b3a06 ("mm/memblock: add memblock memory allocation apis")
> > added a check to determine whether arm_dma_zone_size is exceeding the
> > amount of kernel virtual address space available between the upper 4GB
> > virtual address limit and PAGE_OFFSET in order to provide a suitable
> > definition of MAX_DMA_ADDRESS that should fit within the 32-bit virtual
> > address space. The quantity used for comparison was off by a missing
> > trailing 0, leading to MAX_DMA_ADDRESS to be overflowing a 32-bit
> > quantity.
> >
> > This was caught with the bcm2711 platforms which defines a dma_zone_size
> > of 1GB, and using a PAGE_OFFSET of 0xc000_0000 (CONFIG_VMSPLIT_3G) with
> > CONFIG_DEBUG_VIRTUAL enabled would lead to MAX_DMA_ADDRESS being
> > 0x1_0000_0000 which overflows the unsigned long type used throughout
> > __pa() and __virt_addr_valid(). Because the virtual address passed to
> > __virt_addr_valid() would now be 0, the function would loudly warn, thus
> > making the platform unable to boot properly.
> >
> > Fixes: 26f09e9b3a06 ("mm/memblock: add memblock memory allocation apis")
> > Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
> > ---
> > Changes in v2:
> >
> > - simplify the patch and drop the first patch that attempted to fix an
> >   off by one in the calculation.
>
> Thanks for the update!
>
> > --- a/arch/arm/include/asm/dma.h
> > +++ b/arch/arm/include/asm/dma.h
> > @@ -10,7 +10,7 @@
> >  #else
> >  #define MAX_DMA_ADDRESS        ({ \
> >         extern phys_addr_t arm_dma_zone_size; \
> > -       arm_dma_zone_size && arm_dma_zone_size < (0x10000000 - PAGE_OFFSET) ? \
>                                                   ^^^^^^^^^^
> 0x10000000ULL, as the constant doesn't fit in 32-bit.
> However, both gcc (9.4.0) and sparse don't seem to complain about
> the missing suffix (anymore?).
>
> > +       arm_dma_zone_size && arm_dma_zone_size < (0x100000000 - PAGE_OFFSET) ? \

Obviously my comment applies to the _new_ line, not to the removed
line...

> >                 (PAGE_OFFSET + arm_dma_zone_size) : 0xffffffffUL; })
> >  #endif

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

Re: [PATCH v2] ARM: Fix MAX_DMA_ADDRESS overflow

[Florian Fainelli]

On 7/6/22 12:44, Geert Uytterhoeven wrote:
> Hi Florian,
> 
> On Wed, Jul 6, 2022 at 6:46 PM Florian Fainelli <f.fainelli@gmail.com> wrote:
>> Commit 26f09e9b3a06 ("mm/memblock: add memblock memory allocation apis")
>> added a check to determine whether arm_dma_zone_size is exceeding the
>> amount of kernel virtual address space available between the upper 4GB
>> virtual address limit and PAGE_OFFSET in order to provide a suitable
>> definition of MAX_DMA_ADDRESS that should fit within the 32-bit virtual
>> address space. The quantity used for comparison was off by a missing
>> trailing 0, leading to MAX_DMA_ADDRESS to be overflowing a 32-bit
>> quantity.
>>
>> This was caught with the bcm2711 platforms which defines a dma_zone_size
>> of 1GB, and using a PAGE_OFFSET of 0xc000_0000 (CONFIG_VMSPLIT_3G) with
>> CONFIG_DEBUG_VIRTUAL enabled would lead to MAX_DMA_ADDRESS being
>> 0x1_0000_0000 which overflows the unsigned long type used throughout
>> __pa() and __virt_addr_valid(). Because the virtual address passed to
>> __virt_addr_valid() would now be 0, the function would loudly warn, thus
>> making the platform unable to boot properly.
>>
>> Fixes: 26f09e9b3a06 ("mm/memblock: add memblock memory allocation apis")
>> Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
>> ---
>> Changes in v2:
>>
>> - simplify the patch and drop the first patch that attempted to fix an
>>    off by one in the calculation.
> 
> Thanks for the update!
> 
>> --- a/arch/arm/include/asm/dma.h
>> +++ b/arch/arm/include/asm/dma.h
>> @@ -10,7 +10,7 @@
>>   #else
>>   #define MAX_DMA_ADDRESS        ({ \
>>          extern phys_addr_t arm_dma_zone_size; \
>> -       arm_dma_zone_size && arm_dma_zone_size < (0x10000000 - PAGE_OFFSET) ? \
>                                                    ^^^^^^^^^^
> 0x10000000ULL, as the constant doesn't fit in 32-bit.
> However, both gcc (9.4.0) and sparse don't seem to complain about
> the missing suffix (anymore?).

Thanks, I will the ULL suffix in v3.
-- 
Florian

Re: [PATCH v2] ARM: Fix MAX_DMA_ADDRESS overflow

[Florian Fainelli]

On 7/6/22 12:44, Geert Uytterhoeven wrote:
> Hi Florian,
> 
> On Wed, Jul 6, 2022 at 6:46 PM Florian Fainelli <f.fainelli@gmail.com> wrote:
>> Commit 26f09e9b3a06 ("mm/memblock: add memblock memory allocation apis")
>> added a check to determine whether arm_dma_zone_size is exceeding the
>> amount of kernel virtual address space available between the upper 4GB
>> virtual address limit and PAGE_OFFSET in order to provide a suitable
>> definition of MAX_DMA_ADDRESS that should fit within the 32-bit virtual
>> address space. The quantity used for comparison was off by a missing
>> trailing 0, leading to MAX_DMA_ADDRESS to be overflowing a 32-bit
>> quantity.
>>
>> This was caught with the bcm2711 platforms which defines a dma_zone_size
>> of 1GB, and using a PAGE_OFFSET of 0xc000_0000 (CONFIG_VMSPLIT_3G) with
>> CONFIG_DEBUG_VIRTUAL enabled would lead to MAX_DMA_ADDRESS being
>> 0x1_0000_0000 which overflows the unsigned long type used throughout
>> __pa() and __virt_addr_valid(). Because the virtual address passed to
>> __virt_addr_valid() would now be 0, the function would loudly warn, thus
>> making the platform unable to boot properly.
>>
>> Fixes: 26f09e9b3a06 ("mm/memblock: add memblock memory allocation apis")
>> Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
>> ---
>> Changes in v2:
>>
>> - simplify the patch and drop the first patch that attempted to fix an
>>    off by one in the calculation.
> 
> Thanks for the update!
> 
>> --- a/arch/arm/include/asm/dma.h
>> +++ b/arch/arm/include/asm/dma.h
>> @@ -10,7 +10,7 @@
>>   #else
>>   #define MAX_DMA_ADDRESS        ({ \
>>          extern phys_addr_t arm_dma_zone_size; \
>> -       arm_dma_zone_size && arm_dma_zone_size < (0x10000000 - PAGE_OFFSET) ? \
>                                                    ^^^^^^^^^^
> 0x10000000ULL, as the constant doesn't fit in 32-bit.
> However, both gcc (9.4.0) and sparse don't seem to complain about
> the missing suffix (anymore?).

Thanks, I will the ULL suffix in v3.
-- 
Florian

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Re: [PATCH v2] ARM: Fix MAX_DMA_ADDRESS overflow

[Geert Uytterhoeven]

Hi Florian,

On Wed, Jul 6, 2022 at 10:27 PM Florian Fainelli <f.fainelli@gmail.com> wrote:
> On 7/6/22 12:44, Geert Uytterhoeven wrote:
> > On Wed, Jul 6, 2022 at 6:46 PM Florian Fainelli <f.fainelli@gmail.com> wrote:
> >> Commit 26f09e9b3a06 ("mm/memblock: add memblock memory allocation apis")
> >> added a check to determine whether arm_dma_zone_size is exceeding the
> >> amount of kernel virtual address space available between the upper 4GB
> >> virtual address limit and PAGE_OFFSET in order to provide a suitable
> >> definition of MAX_DMA_ADDRESS that should fit within the 32-bit virtual
> >> address space. The quantity used for comparison was off by a missing
> >> trailing 0, leading to MAX_DMA_ADDRESS to be overflowing a 32-bit
> >> quantity.
> >>
> >> This was caught with the bcm2711 platforms which defines a dma_zone_size
> >> of 1GB, and using a PAGE_OFFSET of 0xc000_0000 (CONFIG_VMSPLIT_3G) with
> >> CONFIG_DEBUG_VIRTUAL enabled would lead to MAX_DMA_ADDRESS being
> >> 0x1_0000_0000 which overflows the unsigned long type used throughout
> >> __pa() and __virt_addr_valid(). Because the virtual address passed to
> >> __virt_addr_valid() would now be 0, the function would loudly warn, thus
> >> making the platform unable to boot properly.
> >>
> >> Fixes: 26f09e9b3a06 ("mm/memblock: add memblock memory allocation apis")
> >> Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
> >> ---
> >> Changes in v2:
> >>
> >> - simplify the patch and drop the first patch that attempted to fix an
> >>    off by one in the calculation.
> >
> > Thanks for the update!
> >
> >> --- a/arch/arm/include/asm/dma.h
> >> +++ b/arch/arm/include/asm/dma.h
> >> @@ -10,7 +10,7 @@
> >>   #else
> >>   #define MAX_DMA_ADDRESS        ({ \
> >>          extern phys_addr_t arm_dma_zone_size; \
> >> -       arm_dma_zone_size && arm_dma_zone_size < (0x10000000 - PAGE_OFFSET) ? \
> >                                                    ^^^^^^^^^^
> > 0x10000000ULL, as the constant doesn't fit in 32-bit.
> > However, both gcc (9.4.0) and sparse don't seem to complain about
> > the missing suffix (anymore?).
>
> Thanks, I will the ULL suffix in v3.

I just remembered the suffix is not needed (but doesn't hurt), because
hexadecimal constants automatically have the right unsigned type.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

Re: [PATCH v2] ARM: Fix MAX_DMA_ADDRESS overflow

[Geert Uytterhoeven]

Hi Florian,

On Wed, Jul 6, 2022 at 10:27 PM Florian Fainelli <f.fainelli@gmail.com> wrote:
> On 7/6/22 12:44, Geert Uytterhoeven wrote:
> > On Wed, Jul 6, 2022 at 6:46 PM Florian Fainelli <f.fainelli@gmail.com> wrote:
> >> Commit 26f09e9b3a06 ("mm/memblock: add memblock memory allocation apis")
> >> added a check to determine whether arm_dma_zone_size is exceeding the
> >> amount of kernel virtual address space available between the upper 4GB
> >> virtual address limit and PAGE_OFFSET in order to provide a suitable
> >> definition of MAX_DMA_ADDRESS that should fit within the 32-bit virtual
> >> address space. The quantity used for comparison was off by a missing
> >> trailing 0, leading to MAX_DMA_ADDRESS to be overflowing a 32-bit
> >> quantity.
> >>
> >> This was caught with the bcm2711 platforms which defines a dma_zone_size
> >> of 1GB, and using a PAGE_OFFSET of 0xc000_0000 (CONFIG_VMSPLIT_3G) with
> >> CONFIG_DEBUG_VIRTUAL enabled would lead to MAX_DMA_ADDRESS being
> >> 0x1_0000_0000 which overflows the unsigned long type used throughout
> >> __pa() and __virt_addr_valid(). Because the virtual address passed to
> >> __virt_addr_valid() would now be 0, the function would loudly warn, thus
> >> making the platform unable to boot properly.
> >>
> >> Fixes: 26f09e9b3a06 ("mm/memblock: add memblock memory allocation apis")
> >> Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
> >> ---
> >> Changes in v2:
> >>
> >> - simplify the patch and drop the first patch that attempted to fix an
> >>    off by one in the calculation.
> >
> > Thanks for the update!
> >
> >> --- a/arch/arm/include/asm/dma.h
> >> +++ b/arch/arm/include/asm/dma.h
> >> @@ -10,7 +10,7 @@
> >>   #else
> >>   #define MAX_DMA_ADDRESS        ({ \
> >>          extern phys_addr_t arm_dma_zone_size; \
> >> -       arm_dma_zone_size && arm_dma_zone_size < (0x10000000 - PAGE_OFFSET) ? \
> >                                                    ^^^^^^^^^^
> > 0x10000000ULL, as the constant doesn't fit in 32-bit.
> > However, both gcc (9.4.0) and sparse don't seem to complain about
> > the missing suffix (anymore?).
>
> Thanks, I will the ULL suffix in v3.

I just remembered the suffix is not needed (but doesn't hurt), because
hexadecimal constants automatically have the right unsigned type.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

_______________________________________________
linux-arm-kernel mailing list
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http://lists.infradead.org/mailman/listinfo/linux-arm-kernel