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 kvm_irq_routing_table.

[1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: kvm@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 include/linux/kvm_host.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index fb6c6109fdca..4944136efaa2 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -664,7 +664,7 @@ struct kvm_irq_routing_table {
 	 * Array indexed by gsi. Each entry contains list of irq chips
 	 * the gsi is connected to.
 	 */
-	struct hlist_head map[];
+	struct hlist_head map[] __counted_by(nr_rt_entries);
 };
 #endif
 
-- 
2.34.1

On Fri, 22 Sep 2023 10:51:21 -0700, 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 kvm_irq_routing_table.
> 
> [...]

Applied to for-next/hardening, thanks!

[1/1] KVM: Annotate struct kvm_irq_routing_table with __counted_by
      https://git.kernel.org/kees/c/bbf75528039a

Take care,

-- 
Kees Cook

On 9/22/23 11:51, 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 kvm_irq_routing_table.
> 
> [1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci
> 
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: kvm@vger.kernel.org
> Signed-off-by: Kees Cook <keescook@chromium.org>

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

Thanks
-- 
Gustavo

> ---
>   include/linux/kvm_host.h | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index fb6c6109fdca..4944136efaa2 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -664,7 +664,7 @@ struct kvm_irq_routing_table {
>   	 * Array indexed by gsi. Each entry contains list of irq chips
>   	 * the gsi is connected to.
>   	 */
> -	struct hlist_head map[];
> +	struct hlist_head map[] __counted_by(nr_rt_entries);
>   };
>   #endif
>