Re: [PATCH 08/14] net: ipa: Annotate struct ipa_power with __counted_by

[Alex Elder <elder@ieee.org>]

On 9/22/23 12:28 PM, Kees Cook wrote:
> Prepare for the coming implementation by GCC and Clang of the __counted_by
> attribute. Flexible array members annotated with __counted_by can have
> their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS
> (for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
> functions).
> 
> As found with Coccinelle[1], add __counted_by for struct ipa_power.

Looks good, thanks.

Reviewed-by: Alex Elder <elder@linaro.org>

Note that there is some interaction between struct ipa_power_data
and struct ipa_power (the former is used to initialize the latter).
Both of these contain flexible arrays counted by another field in
the structure.  It seems possible that the way these are initialized
might need slight modification to allow the compiler to do its
enforcement; if that's the case, please reach out to me.

					-Alex


> [1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci
> 
> Cc: Alex Elder <elder@kernel.org>
> Cc: "David S. Miller" <davem@davemloft.net>
> Cc: Eric Dumazet <edumazet@google.com>
> Cc: Jakub Kicinski <kuba@kernel.org>
> Cc: Paolo Abeni <pabeni@redhat.com>
> Cc: netdev@vger.kernel.org
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
>   drivers/net/ipa/ipa_power.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ipa/ipa_power.c b/drivers/net/ipa/ipa_power.c
> index 0eaa7a7f3343..e223886123ce 100644
> --- a/drivers/net/ipa/ipa_power.c
> +++ b/drivers/net/ipa/ipa_power.c
> @@ -67,7 +67,7 @@ struct ipa_power {
>   	spinlock_t spinlock;	/* used with STOPPED/STARTED power flags */
>   	DECLARE_BITMAP(flags, IPA_POWER_FLAG_COUNT);
>   	u32 interconnect_count;
> -	struct icc_bulk_data interconnect[];
> +	struct icc_bulk_data interconnect[] __counted_by(interconnect_count);
>   };
>   
>   /* Initialize interconnects required for IPA operation */