linux-kernel - Re: [PATCH] KVM: use struct_size() and flex_array_size() helpers in kvm_io_bus_unregister

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Date:   Fri, 18 Sep 2020 19:09:25 -0500
From:   "Gustavo A. R. Silva" <gustavoars@...nel.org>
To:     Rustam Kovhaev <rkovhaev@...il.com>
Cc:     pbonzini@...hat.com, vkuznets@...hat.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, gregkh@...uxfoundation.org,
        stable@...r.kernel.org
Subject: Re: [PATCH] KVM: use struct_size() and flex_array_size() helpers in
 kvm_io_bus_unregister_dev()

On Fri, Sep 18, 2020 at 05:05:00AM -0700, Rustam Kovhaev wrote:
> Make use of the struct_size() helper to avoid any potential type
> mistakes and protect against potential integer overflows
> Make use of the flex_array_size() helper to calculate the size of a
> flexible array member within an enclosing structure
> 
> Cc: stable@...r.kernel.org

I don't think this change applies for -stable.

> Suggested-by: Gustavo A. R. Silva <gustavoars@...nel.org>
> Signed-off-by: Rustam Kovhaev <rkovhaev@...il.com>

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

Thanks!
--
Gustavo

> ---
>  virt/kvm/kvm_main.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index cf88233b819a..68edd25dcb11 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -4350,10 +4350,10 @@ void kvm_io_bus_unregister_dev(struct kvm *kvm, enum kvm_bus bus_idx,
>  	new_bus = kmalloc(struct_size(bus, range, bus->dev_count - 1),
>  			  GFP_KERNEL_ACCOUNT);
>  	if (new_bus) {
> -		memcpy(new_bus, bus, sizeof(*bus) + i * sizeof(struct kvm_io_range));
> +		memcpy(new_bus, bus, struct_size(bus, range, i));
>  		new_bus->dev_count--;
>  		memcpy(new_bus->range + i, bus->range + i + 1,
> -		       (new_bus->dev_count - i) * sizeof(struct kvm_io_range));
> +				flex_array_size(new_bus, range, new_bus->dev_count - i));
>  	} else {
>  		pr_err("kvm: failed to shrink bus, removing it completely\n");
>  		for (j = 0; j < bus->dev_count; j++) {
> -- 
> 2.28.0
>