linux-kernel - Re: [PATCH 2/3] [v2] sfc: fix uninitialized variable use

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Message-ID: <01bad0cf-f67c-3357-d373-cd2b46e26a90@gmail.com>
Date:   Mon, 19 Jun 2023 11:06:54 +0100
From:   Edward Cree <ecree.xilinx@...il.com>
To:     Arnd Bergmann <arnd@...nel.org>,
        Martin Habets <habetsm.xilinx@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Pieter Jansen van Vuuren <pieter.jansen-van-vuuren@....com>,
        Simon Horman <simon.horman@...igine.com>
Cc:     Arnd Bergmann <arnd@...db.de>, netdev@...r.kernel.org,
        linux-net-drivers@....com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] [v2] sfc: fix uninitialized variable use

On 19/06/2023 10:12, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@...db.de>
> 
> The new efx_bind_neigh() function contains a broken code path when IPV6 is
> disabled:
> 
> drivers/net/ethernet/sfc/tc_encap_actions.c:144:7: error: variable 'n' is used uninitialized whenever 'if' condition is true [-Werror,-Wsometimes-uninitialized]
>                 if (encap->type & EFX_ENCAP_FLAG_IPV6) {
>                     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> drivers/net/ethernet/sfc/tc_encap_actions.c:184:8: note: uninitialized use occurs here
>                 if (!n) {
>                      ^
> drivers/net/ethernet/sfc/tc_encap_actions.c:144:3: note: remove the 'if' if its condition is always false
>                 if (encap->type & EFX_ENCAP_FLAG_IPV6) {
>                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> drivers/net/ethernet/sfc/tc_encap_actions.c:141:22: note: initialize the variable 'n' to silence this warning
>                 struct neighbour *n;
>                                    ^
>                                     = NULL
> 
> Change it to use the existing error handling path here.
> 
> Fixes: 7e5e7d800011a ("sfc: neighbour lookup for TC encap action offload")
> Suggested-by: Edward Cree <ecree.xilinx@...il.com>
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

Reviewed-by: Edward Cree <ecree.xilinx@...il.com>

> ---
> v2: use 'goto' instead of incorrectly entering another error path
> ---
>  drivers/net/ethernet/sfc/tc_encap_actions.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/net/ethernet/sfc/tc_encap_actions.c b/drivers/net/ethernet/sfc/tc_encap_actions.c
> index aac259528e73e..7e8bcdb222ad1 100644
> --- a/drivers/net/ethernet/sfc/tc_encap_actions.c
> +++ b/drivers/net/ethernet/sfc/tc_encap_actions.c
> @@ -164,6 +164,7 @@ static int efx_bind_neigh(struct efx_nic *efx,
>  			 */
>  			rc = -EOPNOTSUPP;
>  			NL_SET_ERR_MSG_MOD(extack, "No IPv6 support (neigh bind)");
> +			goto out_free;
>  #endif
>  		} else {
>  			rt = ip_route_output_key(net, &flow4);
>