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* [PATCH] nfp: Prefer struct_size over open coded arithmetic
@ 2021-09-12 13:10 Len Baker
  2021-09-12 19:07 ` Gustavo A. R. Silva
  2021-09-13  8:31 ` Simon Horman
  0 siblings, 2 replies; 3+ messages in thread
From: Len Baker @ 2021-09-12 13:10 UTC (permalink / raw)
  To: Simon Horman, Jakub Kicinski, David S. Miller
  Cc: Len Baker, Kees Cook, Gustavo A. R. Silva, oss-drivers, netdev,
	linux-hardening, linux-kernel

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 <len.baker@gmx.com>
---
 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


^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: [PATCH] nfp: Prefer struct_size over open coded arithmetic
  2021-09-12 13:10 [PATCH] nfp: Prefer struct_size over open coded arithmetic Len Baker
@ 2021-09-12 19:07 ` Gustavo A. R. Silva
  2021-09-13  8:31 ` Simon Horman
  1 sibling, 0 replies; 3+ messages in thread
From: Gustavo A. R. Silva @ 2021-09-12 19:07 UTC (permalink / raw)
  To: Len Baker
  Cc: Simon Horman, Jakub Kicinski, David S. Miller, Kees Cook,
	oss-drivers, netdev, linux-hardening, linux-kernel

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 <len.baker@gmx.com>

Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>

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
> 

^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: [PATCH] nfp: Prefer struct_size over open coded arithmetic
  2021-09-12 13:10 [PATCH] nfp: Prefer struct_size over open coded arithmetic Len Baker
  2021-09-12 19:07 ` Gustavo A. R. Silva
@ 2021-09-13  8:31 ` Simon Horman
  1 sibling, 0 replies; 3+ messages in thread
From: Simon Horman @ 2021-09-13  8:31 UTC (permalink / raw)
  To: Len Baker
  Cc: Jakub Kicinski, David S. Miller, Kees Cook, Gustavo A. R. Silva,
	oss-drivers, netdev, linux-hardening, linux-kernel

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 <len.baker@gmx.com>

Reviewed-by: Simon Horman <simon.horman@corigine.com>

> ---
>  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
> 

^ permalink raw reply	[flat|nested] 3+ messages in thread

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2021-09-12 13:10 [PATCH] nfp: Prefer struct_size over open coded arithmetic Len Baker
2021-09-12 19:07 ` Gustavo A. R. Silva
2021-09-13  8:31 ` Simon Horman

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