[PATCH] mlxsw: core_acl_flex_actions: Split memcpy() of struct flow_action_cookie flexible array

[PATCH] mlxsw: core_acl_flex_actions: Split memcpy() of struct flow_action_cookie flexible array

[Kees Cook]

To work around a misbehavior of the compiler's ability to see into
composite flexible array structs (as detailed in the coming memcpy()
hardening series[1]), split the memcpy() of the header and the payload
so no false positive run-time overflow warning will be generated.

[1] https://lore.kernel.org/linux-hardening/20220901065914.1417829-2-keescook@chromium.org

Cc: Ido Schimmel <idosch@nvidia.com>
Cc: Petr Machata <petrm@nvidia.com>
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/ethernet/mellanox/mlxsw/core_acl_flex_actions.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlxsw/core_acl_flex_actions.c b/drivers/net/ethernet/mellanox/mlxsw/core_acl_flex_actions.c
index 636db9a87457..9dfe7148199f 100644
--- a/drivers/net/ethernet/mellanox/mlxsw/core_acl_flex_actions.c
+++ b/drivers/net/ethernet/mellanox/mlxsw/core_acl_flex_actions.c
@@ -737,8 +737,9 @@ mlxsw_afa_cookie_create(struct mlxsw_afa *mlxsw_afa,
 	if (!cookie)
 		return ERR_PTR(-ENOMEM);
 	refcount_set(&cookie->ref_count, 1);
-	memcpy(&cookie->fa_cookie, fa_cookie,
-	       sizeof(*fa_cookie) + fa_cookie->cookie_len);
+	cookie->fa_cookie = *fa_cookie;
+	memcpy(cookie->fa_cookie.cookie, fa_cookie->cookie,
+	       fa_cookie->cookie_len);
 
 	err = rhashtable_insert_fast(&mlxsw_afa->cookie_ht, &cookie->ht_node,
 				     mlxsw_afa_cookie_ht_params);
-- 
2.34.1

Re: [PATCH] mlxsw: core_acl_flex_actions: Split memcpy() of struct flow_action_cookie flexible array

[Gustavo A. R. Silva]

On Mon, Sep 26, 2022 at 05:40:33PM -0700, Kees Cook wrote:
> To work around a misbehavior of the compiler's ability to see into
> composite flexible array structs (as detailed in the coming memcpy()
> hardening series[1]), split the memcpy() of the header and the payload
> so no false positive run-time overflow warning will be generated.
> 
> [1] https://lore.kernel.org/linux-hardening/20220901065914.1417829-2-keescook@chromium.org
> 
> Cc: Ido Schimmel <idosch@nvidia.com>
> Cc: Petr Machata <petrm@nvidia.com>
> 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>


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

Thanks!
--
Gustavo

> ---
>  drivers/net/ethernet/mellanox/mlxsw/core_acl_flex_actions.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/mellanox/mlxsw/core_acl_flex_actions.c b/drivers/net/ethernet/mellanox/mlxsw/core_acl_flex_actions.c
> index 636db9a87457..9dfe7148199f 100644
> --- a/drivers/net/ethernet/mellanox/mlxsw/core_acl_flex_actions.c
> +++ b/drivers/net/ethernet/mellanox/mlxsw/core_acl_flex_actions.c
> @@ -737,8 +737,9 @@ mlxsw_afa_cookie_create(struct mlxsw_afa *mlxsw_afa,
>  	if (!cookie)
>  		return ERR_PTR(-ENOMEM);
>  	refcount_set(&cookie->ref_count, 1);
> -	memcpy(&cookie->fa_cookie, fa_cookie,
> -	       sizeof(*fa_cookie) + fa_cookie->cookie_len);
> +	cookie->fa_cookie = *fa_cookie;
> +	memcpy(cookie->fa_cookie.cookie, fa_cookie->cookie,
> +	       fa_cookie->cookie_len);
>  
>  	err = rhashtable_insert_fast(&mlxsw_afa->cookie_ht, &cookie->ht_node,
>  				     mlxsw_afa_cookie_ht_params);
> -- 
> 2.34.1
> 

Re: [PATCH] mlxsw: core_acl_flex_actions: Split memcpy() of struct flow_action_cookie flexible array

[Petr Machata]

Kees Cook <keescook@chromium.org> writes:

> To work around a misbehavior of the compiler's ability to see into
> composite flexible array structs (as detailed in the coming memcpy()
> hardening series[1]), split the memcpy() of the header and the payload
> so no false positive run-time overflow warning will be generated.
>
> [1] https://lore.kernel.org/linux-hardening/20220901065914.1417829-2-keescook@chromium.org
>
> Cc: Ido Schimmel <idosch@nvidia.com>
> Cc: Petr Machata <petrm@nvidia.com>
> 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>

Reviewed-by: Petr Machata <petrm@nvidia.com>

Re: [PATCH] mlxsw: core_acl_flex_actions: Split memcpy() of struct flow_action_cookie flexible array

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net-next.git (master)
by Jakub Kicinski <kuba@kernel.org>:

On Mon, 26 Sep 2022 17:40:33 -0700 you wrote:
> To work around a misbehavior of the compiler's ability to see into
> composite flexible array structs (as detailed in the coming memcpy()
> hardening series[1]), split the memcpy() of the header and the payload
> so no false positive run-time overflow warning will be generated.
> 
> [1] https://lore.kernel.org/linux-hardening/20220901065914.1417829-2-keescook@chromium.org
> 
> [...]

Here is the summary with links:
  - mlxsw: core_acl_flex_actions: Split memcpy() of struct flow_action_cookie flexible array
    https://git.kernel.org/netdev/net-next/c/d89318bbdf2b

You are awesome, thank you!
-- 
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