One of the more common cases of allocation size calculations is finding
the size of a structure that has a zero-sized array at the end, along
with memory for some number of elements for that array. For example:
struct nd_region {
...
struct nd_mapping mapping[0];
};
instance = kzalloc(sizeof(struct nd_region) + sizeof(struct nd_mapping) *
count, GFP_KERNEL);
Instead of leaving these open-coded and prone to type mistakes, we can
now use the new struct_size() helper:
instance = kzalloc(struct_size(instance, mapping, count), GFP_KERNEL);
This code was detected with the help of Coccinelle.
Signed-off-by: Gustavo A. R. Silva <[email protected]>
---
drivers/nvdimm/region_devs.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)
diff --git a/drivers/nvdimm/region_devs.c b/drivers/nvdimm/region_devs.c
index b4ef7d9ff22e..88becc87e234 100644
--- a/drivers/nvdimm/region_devs.c
+++ b/drivers/nvdimm/region_devs.c
@@ -1027,10 +1027,9 @@ static struct nd_region *nd_region_create(struct nvdimm_bus *nvdimm_bus,
}
region_buf = ndbr;
} else {
- nd_region = kzalloc(sizeof(struct nd_region)
- + sizeof(struct nd_mapping)
- * ndr_desc->num_mappings,
- GFP_KERNEL);
+ nd_region = kzalloc(struct_size(nd_region, mapping,
+ ndr_desc->num_mappings),
+ GFP_KERNEL);
region_buf = nd_region;
}
--
2.21.0
Hi all,
Friendly ping:
Who can take this, please?
Thanks
--
Gustavo
On 6/10/19 4:06 PM, Gustavo A. R. Silva wrote:
> One of the more common cases of allocation size calculations is finding
> the size of a structure that has a zero-sized array at the end, along
> with memory for some number of elements for that array. For example:
>
> struct nd_region {
> ...
> struct nd_mapping mapping[0];
> };
>
> instance = kzalloc(sizeof(struct nd_region) + sizeof(struct nd_mapping) *
> count, GFP_KERNEL);
>
> Instead of leaving these open-coded and prone to type mistakes, we can
> now use the new struct_size() helper:
>
> instance = kzalloc(struct_size(instance, mapping, count), GFP_KERNEL);
>
> This code was detected with the help of Coccinelle.
>
> Signed-off-by: Gustavo A. R. Silva <[email protected]>
> ---
> drivers/nvdimm/region_devs.c | 7 +++----
> 1 file changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/nvdimm/region_devs.c b/drivers/nvdimm/region_devs.c
> index b4ef7d9ff22e..88becc87e234 100644
> --- a/drivers/nvdimm/region_devs.c
> +++ b/drivers/nvdimm/region_devs.c
> @@ -1027,10 +1027,9 @@ static struct nd_region *nd_region_create(struct nvdimm_bus *nvdimm_bus,
> }
> region_buf = ndbr;
> } else {
> - nd_region = kzalloc(sizeof(struct nd_region)
> - + sizeof(struct nd_mapping)
> - * ndr_desc->num_mappings,
> - GFP_KERNEL);
> + nd_region = kzalloc(struct_size(nd_region, mapping,
> + ndr_desc->num_mappings),
> + GFP_KERNEL);
> region_buf = nd_region;
> }
>
>
On Mon, 2019-06-10 at 16:06 -0500, Gustavo A. R. Silva wrote:
> One of the more common cases of allocation size calculations is
> finding
> the size of a structure that has a zero-sized array at the end, along
> with memory for some number of elements for that array. For example:
>
> struct nd_region {
> ...
> struct nd_mapping mapping[0];
> };
>
> instance = kzalloc(sizeof(struct nd_region) + sizeof(struct
> nd_mapping) *
> count, GFP_KERNEL);
>
> Instead of leaving these open-coded and prone to type mistakes, we can
> now use the new struct_size() helper:
>
> instance = kzalloc(struct_size(instance, mapping, count), GFP_KERNEL);
>
> This code was detected with the help of Coccinelle.
>
> Signed-off-by: Gustavo A. R. Silva <[email protected]>
> ---
> drivers/nvdimm/region_devs.c | 7 +++----
> 1 file changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/nvdimm/region_devs.c
> b/drivers/nvdimm/region_devs.c
> index b4ef7d9ff22e..88becc87e234 100644
> --- a/drivers/nvdimm/region_devs.c
> +++ b/drivers/nvdimm/region_devs.c
> @@ -1027,10 +1027,9 @@ static struct nd_region
> *nd_region_create(struct nvdimm_bus *nvdimm_bus,
> }
> region_buf = ndbr;
> } else {
> - nd_region = kzalloc(sizeof(struct nd_region)
> - + sizeof(struct nd_mapping)
> - * ndr_desc->num_mappings,
> - GFP_KERNEL);
> + nd_region = kzalloc(struct_size(nd_region, mapping,
> + ndr_desc->num_mappings),
> + GFP_KERNEL);
> region_buf = nd_region;
> }
>
Hi Gustavo,
The patch looks good to me, however it looks like it might've missed
some instances where this replacement can be performed?
One is just a few lines below from the above, in the 'else' block[1].
Additionally, maybe the Coccinelle script can be augmented to catch
devm_kzalloc instances as well - there is one of those in this file[2].
Thanks,
-Vishal
[1]: https://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm.git/tree/drivers/nvdimm/region_devs.c#n1030
[2]: https://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm.git/tree/drivers/nvdimm/region_devs.c#n96
Hi Vishal,
On 8/28/19 1:51 PM, Verma, Vishal L wrote:
[..]
>
> Hi Gustavo,
>
> The patch looks good to me, however it looks like it might've missed
> some instances where this replacement can be performed?
>
struct_size() does not apply to those scenarios. See below...
>
> [1]: https://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm.git/tree/drivers/nvdimm/region_devs.c#n1030
struct_size() only applies to structures of the following kind:
struct foo {
int stuff;
struct boo entry[];
};
and this scenario includes two different structures:
struct nd_region {
...
struct nd_mapping mapping[0];
};
struct nd_blk_region {
...
struct nd_region nd_region;
};
> [2]: https://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm.git/tree/drivers/nvdimm/region_devs.c#n96
>
In this scenario struct_size() does not apply directly because of the following
logic before the call to devm_kzalloc():
size_t flush_data_size = sizeof(void *);
[..]
for (i = 0; i < nd_region->ndr_mappings; i++) {
[..]
/* at least one null hint slot per-dimm for the "no-hint" case */
flush_data_size += sizeof(void *);
[..]
flush_data_size += nvdimm->num_flush * sizeof(void *);
}
Thanks
--
Gustavo
On Wed, Aug 28, 2019 at 01:30:24PM -0500, Gustavo A. R. Silva wrote:
> Hi all,
>
> Friendly ping:
>
> Who can take this, please?
>
> Thanks
> --
> Gustavo
>
> On 6/10/19 4:06 PM, Gustavo A. R. Silva wrote:
> > One of the more common cases of allocation size calculations is finding
> > the size of a structure that has a zero-sized array at the end, along
> > with memory for some number of elements for that array. For example:
> >
> > struct nd_region {
> > ...
> > struct nd_mapping mapping[0];
> > };
> >
> > instance = kzalloc(sizeof(struct nd_region) + sizeof(struct nd_mapping) *
> > count, GFP_KERNEL);
> >
> > Instead of leaving these open-coded and prone to type mistakes, we can
> > now use the new struct_size() helper:
> >
> > instance = kzalloc(struct_size(instance, mapping, count), GFP_KERNEL);
> >
> > This code was detected with the help of Coccinelle.
> >
> > Signed-off-by: Gustavo A. R. Silva <[email protected]>
FWIW,
Reviewed-by: Kees Cook <[email protected]>
-Kees
> > ---
> > drivers/nvdimm/region_devs.c | 7 +++----
> > 1 file changed, 3 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/nvdimm/region_devs.c b/drivers/nvdimm/region_devs.c
> > index b4ef7d9ff22e..88becc87e234 100644
> > --- a/drivers/nvdimm/region_devs.c
> > +++ b/drivers/nvdimm/region_devs.c
> > @@ -1027,10 +1027,9 @@ static struct nd_region *nd_region_create(struct nvdimm_bus *nvdimm_bus,
> > }
> > region_buf = ndbr;
> > } else {
> > - nd_region = kzalloc(sizeof(struct nd_region)
> > - + sizeof(struct nd_mapping)
> > - * ndr_desc->num_mappings,
> > - GFP_KERNEL);
> > + nd_region = kzalloc(struct_size(nd_region, mapping,
> > + ndr_desc->num_mappings),
> > + GFP_KERNEL);
> > region_buf = nd_region;
> > }
> >
> >
--
Kees Cook
On Wed, 2019-08-28 at 14:36 -0500, Gustavo A. R. Silva wrote:
> struct_size() does not apply to those scenarios. See below...
>
> > [1]:
> > https://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm.git/tree/drivers/nvdimm/region_devs.c#n1030
>
> struct_size() only applies to structures of the following kind:
>
> struct foo {
> int stuff;
> struct boo entry[];
> };
>
> and this scenario includes two different structures:
>
> struct nd_region {
> ...
> struct nd_mapping mapping[0];
> };
>
> struct nd_blk_region {
> ...
> struct nd_region nd_region;
> };
Yep - I neglected to actually look at the structures involved - you're
right, it doesn't apply here.
>
> > [2]:
> > https://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm.git/tree/drivers/nvdimm/region_devs.c#n96
> >
>
> In this scenario struct_size() does not apply directly because of the
> following
> logic before the call to devm_kzalloc():
Agreed, I missed that the calculation was more involved here.
Thanks for the clarifications, you can add:
Reviewed-by: Vishal Verma <[email protected]>
On Wed, Aug 28, 2019 at 1:24 PM Verma, Vishal L
<[email protected]> wrote:
>
> On Wed, 2019-08-28 at 14:36 -0500, Gustavo A. R. Silva wrote:
>
> > struct_size() does not apply to those scenarios. See below...
> >
> > > [1]:
> > > https://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm.git/tree/drivers/nvdimm/region_devs.c#n1030
> >
> > struct_size() only applies to structures of the following kind:
> >
> > struct foo {
> > int stuff;
> > struct boo entry[];
> > };
> >
> > and this scenario includes two different structures:
> >
> > struct nd_region {
> > ...
> > struct nd_mapping mapping[0];
> > };
> >
> > struct nd_blk_region {
> > ...
> > struct nd_region nd_region;
> > };
>
> Yep - I neglected to actually look at the structures involved - you're
> right, it doesn't apply here.
>
> >
> > > [2]:
> > > https://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm.git/tree/drivers/nvdimm/region_devs.c#n96
> > >
> >
> > In this scenario struct_size() does not apply directly because of the
> > following
> > logic before the call to devm_kzalloc():
>
> Agreed, I missed that the calculation was more involved here.
>
> Thanks for the clarifications, you can add:
> Reviewed-by: Vishal Verma <[email protected]>
Thanks, applied.