From: Arnd Bergmann <[email protected]>
The comparison against SIZE_MAX produces a harmless warning on 64-bit
architectures:
drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c:185:16: error: result of comparison of constant 419244183493398898 with expression of type 'unsigned int' is always false [-Werror,-Wtautological-constant-out-of-range-compare]
if (num_pages > (SIZE_MAX - sizeof(struct pagelist) -
~~~~~~~~~ ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Shut up that warning by adding a cast to a longer type.
Fixes: ca641bae6da9 ("staging: vc04_services: prevent integer overflow in create_pagelist()")
Signed-off-by: Arnd Bergmann <[email protected]>
---
drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
index b25369a13452..967f10b9582a 100644
--- a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
+++ b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
@@ -182,7 +182,7 @@ create_pagelist(char *buf, char __user *ubuf,
offset = (uintptr_t)ubuf & (PAGE_SIZE - 1);
num_pages = DIV_ROUND_UP(count + offset, PAGE_SIZE);
- if (num_pages > (SIZE_MAX - sizeof(struct pagelist) -
+ if ((size_t)num_pages > (SIZE_MAX - sizeof(struct pagelist) -
sizeof(struct vchiq_pagelist_info)) /
(sizeof(u32) + sizeof(pages[0]) +
sizeof(struct scatterlist)))
--
2.29.2
On Mon, Sep 27, 2021 at 01:36:56PM +0200, Arnd Bergmann wrote:
> From: Arnd Bergmann <[email protected]>
>
> The comparison against SIZE_MAX produces a harmless warning on 64-bit
> architectures:
>
> drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c:185:16: error: result of comparison of constant 419244183493398898 with expression of type 'unsigned int' is always false [-Werror,-Wtautological-constant-out-of-range-compare]
> if (num_pages > (SIZE_MAX - sizeof(struct pagelist) -
> ~~~~~~~~~ ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> Shut up that warning by adding a cast to a longer type.
>
> Fixes: ca641bae6da9 ("staging: vc04_services: prevent integer overflow in create_pagelist()")
> Signed-off-by: Arnd Bergmann <[email protected]>
> ---
> drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
> index b25369a13452..967f10b9582a 100644
> --- a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
> +++ b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
> @@ -182,7 +182,7 @@ create_pagelist(char *buf, char __user *ubuf,
> offset = (uintptr_t)ubuf & (PAGE_SIZE - 1);
> num_pages = DIV_ROUND_UP(count + offset, PAGE_SIZE);
>
> - if (num_pages > (SIZE_MAX - sizeof(struct pagelist) -
> + if ((size_t)num_pages > (SIZE_MAX - sizeof(struct pagelist) -
> sizeof(struct vchiq_pagelist_info)) /
> (sizeof(u32) + sizeof(pages[0]) +
> sizeof(struct scatterlist)))
The temptation would be to declare "num_pages" as size_t instead of
adding this cost. But then something will complain about the
"pagelistinfo->num_pages = num_pages;" assignment because
"pagelistinfo->num_pages" is a u32.
The next temptation is to change the SIZE_MAX to UINT_MAX. I didn't
do that originally because I can't test this and I was trying not to
break things... We probably still don't want to break things, but maybe
there is someone who is more familiar with this who knows if UINT_MAX is
okay?
regards,
dan carpenter
Hi Dan,
On 27/09/2021 13:26, Dan Carpenter wrote:
> On Mon, Sep 27, 2021 at 01:36:56PM +0200, Arnd Bergmann wrote:
>> From: Arnd Bergmann <[email protected]>
>>
>> The comparison against SIZE_MAX produces a harmless warning on 64-bit
>> architectures:
>>
>> drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c:185:16: error: result of comparison of constant 419244183493398898 with expression of type 'unsigned int' is always false [-Werror,-Wtautological-constant-out-of-range-compare]
>> if (num_pages > (SIZE_MAX - sizeof(struct pagelist) -
>> ~~~~~~~~~ ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>
>> Shut up that warning by adding a cast to a longer type.
>>
>> Fixes: ca641bae6da9 ("staging: vc04_services: prevent integer overflow in create_pagelist()")
>> Signed-off-by: Arnd Bergmann <[email protected]>
>> ---
>> drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
>> index b25369a13452..967f10b9582a 100644
>> --- a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
>> +++ b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
>> @@ -182,7 +182,7 @@ create_pagelist(char *buf, char __user *ubuf,
>> offset = (uintptr_t)ubuf & (PAGE_SIZE - 1);
>> num_pages = DIV_ROUND_UP(count + offset, PAGE_SIZE);
>>
>> - if (num_pages > (SIZE_MAX - sizeof(struct pagelist) -
>> + if ((size_t)num_pages > (SIZE_MAX - sizeof(struct pagelist) -
>> sizeof(struct vchiq_pagelist_info)) /
>> (sizeof(u32) + sizeof(pages[0]) +
>> sizeof(struct scatterlist)))
>
> The temptation would be to declare "num_pages" as size_t instead of
> adding this cost. But then something will complain about the
> "pagelistinfo->num_pages = num_pages;" assignment because
> "pagelistinfo->num_pages" is a u32.
>
> The next temptation is to change the SIZE_MAX to UINT_MAX. I didn't
> do that originally because I can't test this and I was trying not to
> break things... We probably still don't want to break things, but maybe
> there is someone who is more familiar with this who knows if UINT_MAX is
> okay?
The VPU can't address more than 1GB directly, so UINT_MAX is more than sufficient.
Phil
On Mon, Sep 27, 2021 at 3:22 PM Phil Elwell <[email protected]> wrote:
> On 27/09/2021 13:26, Dan Carpenter wrote:
> > On Mon, Sep 27, 2021 at 01:36:56PM +0200, Arnd Bergmann wrote:
> >> From: Arnd Bergmann <[email protected]>
> >>
> >> - if (num_pages > (SIZE_MAX - sizeof(struct pagelist) -
> >> + if ((size_t)num_pages > (SIZE_MAX - sizeof(struct pagelist) -
> >> sizeof(struct vchiq_pagelist_info)) /
> >> (sizeof(u32) + sizeof(pages[0]) +
> >> sizeof(struct scatterlist)))
> >
> > The temptation would be to declare "num_pages" as size_t instead of
> > adding this cost. But then something will complain about the
> > "pagelistinfo->num_pages = num_pages;" assignment because
> > "pagelistinfo->num_pages" is a u32.
> >
> > The next temptation is to change the SIZE_MAX to UINT_MAX. I didn't
> > do that originally because I can't test this and I was trying not to
> > break things... We probably still don't want to break things, but maybe
> > there is someone who is more familiar with this who knows if UINT_MAX is
> > okay?
>
> The VPU can't address more than 1GB directly, so UINT_MAX is more than sufficient.
Is there a macro that already defines that 1GB size, or maybe an even smaller
value that makes sense as an upper bound?
Arnd