Re: [PATCH v2] perf/x86/amd/uncore: Use kcalloc*() instead of kzalloc*()

[Ingo Molnar]

* Erick Archer <erick.archer@xxxxxxxxxxx> 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 purpose specific kcalloc*() function instead of the argument
> size * count in the kzalloc*() function.
> 
> [1] https://www.kernel.org/doc/html/next/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments
> 
> Link: https://github.com/KSPP/linux/issues/162
> Reviewed-by: Gustavo A. R. Silva <gustavoars@xxxxxxxxxx>
> Signed-off-by: Erick Archer <erick.archer@xxxxxxxxxxx>
> ---
> Changes in v2:
> - Add the "Reviewed-by:" tag.
> - Rebase against linux-next.
> 
> Previous versions:
> v1 -> https://lore.kernel.org/linux-hardening/20240116125813.3754-1-erick.archer@xxxxxxx/
> 
> Hi everyone,
> 
> This patch seems to be lost. Gustavo reviewed it on January 16, 2024
> but the patch has not been applied since.
> 
> Thanks,
> Erick
> ---
>  arch/x86/events/amd/uncore.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/events/amd/uncore.c b/arch/x86/events/amd/uncore.c
> index 4ccb8fa483e6..61c0a2114183 100644
> --- a/arch/x86/events/amd/uncore.c
> +++ b/arch/x86/events/amd/uncore.c
> @@ -479,8 +479,8 @@ static int amd_uncore_ctx_init(struct amd_uncore *uncore, unsigned int cpu)
>  				goto fail;
>  
>  			curr->cpu = cpu;
> -			curr->events = kzalloc_node(sizeof(*curr->events) *
> -						    pmu->num_counters,
> +			curr->events = kcalloc_node(pmu->num_counters,
> +						    sizeof(*curr->events),
>  						    GFP_KERNEL, node);
>  			if (!curr->events) {
>  				kfree(curr);
> @@ -928,7 +928,7 @@ int amd_uncore_umc_ctx_init(struct amd_uncore *uncore, unsigned int cpu)
>  		uncore->num_pmus += group_num_pmus[gid];
>  	}
>  
> -	uncore->pmus = kzalloc(sizeof(*uncore->pmus) * uncore->num_pmus,
> +	uncore->pmus = kcalloc(uncore->num_pmus, sizeof(*uncore->pmus),
>  			       GFP_KERNEL);
>  	if (!uncore->pmus) {
>  		uncore->num_pmus = 0;

This change is nonsense, kzalloc() is a perfectly usable interface, and 
none of the arguments are user-controlled, so I don't see how there 
could be a real overflow bug here.

Thanks,

	Ingo