2021-09-12 13:13:47

by Len Baker

Subject: [PATCH] nfp: Prefer struct_size over open coded arithmetic

As noted in the "Deprecated Interfaces, Language Features, Attributes,
and Conventions" documentation [1], size calculations (especially
multiplication) should not be performed in memory allocator (or similar)
function arguments due to the risk of them overflowing. This could lead
to values wrapping around and a smaller allocation being made than the
caller was expecting. Using those allocations could lead to linear
overflows of heap memory and other misbehaviors.

So, use the struct_size() helper to do the arithmetic instead of the
argument "size + count * size" in the kzalloc() function.

[1] https://www.kernel.org/doc/html/v5.14/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments

Signed-off-by: Len Baker <[email protected]>
---
drivers/net/ethernet/netronome/nfp/nfp_net_repr.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/netronome/nfp/nfp_net_repr.c b/drivers/net/ethernet/netronome/nfp/nfp_net_repr.c
index 3b8e675087de..369f6ae700c7 100644
--- a/drivers/net/ethernet/netronome/nfp/nfp_net_repr.c
+++ b/drivers/net/ethernet/netronome/nfp/nfp_net_repr.c
@@ -499,8 +499,7 @@ struct nfp_reprs *nfp_reprs_alloc(unsigned int num_reprs)
{
struct nfp_reprs *reprs;

- reprs = kzalloc(sizeof(*reprs) +
- num_reprs * sizeof(struct net_device *), GFP_KERNEL);
+ reprs = kzalloc(struct_size(reprs, reprs, num_reprs), GFP_KERNEL);
if (!reprs)
return NULL;
reprs->num_reprs = num_reprs;
--
2.25.1

2021-09-12 19:10:10

by Gustavo A. R. Silva

Subject: Re: [PATCH] nfp: Prefer struct_size over open coded arithmetic

On Sun, Sep 12, 2021 at 03:10:57PM +0200, Len Baker wrote:
> As noted in the "Deprecated Interfaces, Language Features, Attributes,
> and Conventions" documentation [1], size calculations (especially
> multiplication) should not be performed in memory allocator (or similar)
> function arguments due to the risk of them overflowing. This could lead
> to values wrapping around and a smaller allocation being made than the
> caller was expecting. Using those allocations could lead to linear
> overflows of heap memory and other misbehaviors.
>
> So, use the struct_size() helper to do the arithmetic instead of the
> argument "size + count * size" in the kzalloc() function.
>
> [1] https://www.kernel.org/doc/html/v5.14/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments
>
> Signed-off-by: Len Baker <[email protected]>

Reviewed-by: Gustavo A. R. Silva <[email protected]>

I'll take this in my -next tree. :)

Thanks, Len.
--
Gustavo

> ---
> drivers/net/ethernet/netronome/nfp/nfp_net_repr.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/drivers/net/ethernet/netronome/nfp/nfp_net_repr.c b/drivers/net/ethernet/netronome/nfp/nfp_net_repr.c
> index 3b8e675087de..369f6ae700c7 100644
> --- a/drivers/net/ethernet/netronome/nfp/nfp_net_repr.c
> +++ b/drivers/net/ethernet/netronome/nfp/nfp_net_repr.c
> @@ -499,8 +499,7 @@ struct nfp_reprs *nfp_reprs_alloc(unsigned int num_reprs)
> {
> struct nfp_reprs *reprs;
>
> - reprs = kzalloc(sizeof(*reprs) +
> - num_reprs * sizeof(struct net_device *), GFP_KERNEL);
> + reprs = kzalloc(struct_size(reprs, reprs, num_reprs), GFP_KERNEL);
> if (!reprs)
> return NULL;
> reprs->num_reprs = num_reprs;
> --
> 2.25.1
>

2021-09-13 08:34:09

by Simon Horman

Subject: Re: [PATCH] nfp: Prefer struct_size over open coded arithmetic

On Sun, Sep 12, 2021 at 03:10:57PM +0200, Len Baker wrote:
> As noted in the "Deprecated Interfaces, Language Features, Attributes,
> and Conventions" documentation [1], size calculations (especially
> multiplication) should not be performed in memory allocator (or similar)
> function arguments due to the risk of them overflowing. This could lead
> to values wrapping around and a smaller allocation being made than the
> caller was expecting. Using those allocations could lead to linear
> overflows of heap memory and other misbehaviors.
>
> So, use the struct_size() helper to do the arithmetic instead of the
> argument "size + count * size" in the kzalloc() function.
>
> [1] https://www.kernel.org/doc/html/v5.14/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments
>
> Signed-off-by: Len Baker <[email protected]>

Reviewed-by: Simon Horman <[email protected]>

> ---
> drivers/net/ethernet/netronome/nfp/nfp_net_repr.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/drivers/net/ethernet/netronome/nfp/nfp_net_repr.c b/drivers/net/ethernet/netronome/nfp/nfp_net_repr.c
> index 3b8e675087de..369f6ae700c7 100644
> --- a/drivers/net/ethernet/netronome/nfp/nfp_net_repr.c
> +++ b/drivers/net/ethernet/netronome/nfp/nfp_net_repr.c
> @@ -499,8 +499,7 @@ struct nfp_reprs *nfp_reprs_alloc(unsigned int num_reprs)
> {
> struct nfp_reprs *reprs;
>
> - reprs = kzalloc(sizeof(*reprs) +
> - num_reprs * sizeof(struct net_device *), GFP_KERNEL);
> + reprs = kzalloc(struct_size(reprs, reprs, num_reprs), GFP_KERNEL);
> if (!reprs)
> return NULL;
> reprs->num_reprs = num_reprs;
> --
> 2.25.1
>