Re: [PATCH v2] x86/resctrl: Fix potential memory leak

[Borislav Petkov <bp@alien8.de>]

On Fri, Dec 20, 2019 at 08:43:58AM -0800, Shakeel Butt wrote:
> The set_cache_qos_cfg() is leaking memory when the given level is not
> RDT_RESOURCE_L3 or RDT_RESOURCE_L2. However at the moment, this function
> is called with only valid levels but to make it more robust and future
> proof, we should be handling the error path gracefully.
> 
> Fixes: 99adde9b370de ("x86/intel_rdt: Enable L2 CDP in MSR IA32_L2_QOS_CFG")
> Signed-off-by: Shakeel Butt <shakeelb@google.com>
> Acked-by: Fenghua Yu <fenghua.yu@intel.com>
> ---
> Changes since v1:
> - Updated the commit message
> 
> 
>  arch/x86/kernel/cpu/resctrl/rdtgroup.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> index 2e3b06d6bbc6..a0c279c7f4b9 100644
> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> @@ -1748,8 +1748,10 @@ static int set_cache_qos_cfg(int level, bool enable)
>  		update = l3_qos_cfg_update;
>  	else if (level == RDT_RESOURCE_L2)
>  		update = l2_qos_cfg_update;
> -	else
> +	else {
> +		free_cpumask_var(cpu_mask);
>  		return -EINVAL;
> +	}

And why can't the level check happen first and the allocation second,
thus needing to allocate the cpu mask only when the level is valid?

-- 
Regards/Gruss,
    Boris.

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