Re: [PATCH v6 1/4] cacheinfo: Check for null last-level cache info

[Borislav Petkov]

On Wed, Sep 04, 2024 at 11:00:33PM -0700, Ricardo Neri wrote:
> Before determining the validity of the last-level cache info, ensure that
> it has been allocated. Simply checking for non-zero cache_leaves() is not
> sufficient, as some architectures (e.g., Intel processors) have non-zero
> cache_leaves() before allocation.
>
> Dereferencing NULL cacheinfo can occur in update_per_cpu_data_slice_size().
> This function iterates over all online CPUs. However, a CPU may have come
> online recently, but its cacheinfo may not have been allocated yet.
> 
> Reviewed-by: Andreas Herrmann <aherrmann@xxxxxxx>
> Reviewed-by: Sudeep Holla <sudeep.holla@xxxxxxx>
> Tested-by: Andreas Herrmann <aherrmann@xxxxxxx>
> Signed-off-by: Ricardo Neri <ricardo.neri-calderon@xxxxxxxxxxxxxxx>

While at it, pls fix the formatting insanity of allocate_cache_info() into:

static inline int allocate_cache_info(int cpu)
{
        per_cpu_cacheinfo(cpu) = kcalloc(cache_leaves(cpu), sizeof(struct cacheinfo), GFP_ATOMIC);
        if (!per_cpu_cacheinfo(cpu)) {
                cache_leaves(cpu) = 0;
                return -ENOMEM;
        }
            
        return 0;
}

Thx.

-- 
Regards/Gruss,
    Boris.

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