linux-kernel - Re: [PATCH] selinux: avoid uninitialized variable warning

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Date:   Fri, 22 Mar 2019 08:17:45 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Paul Moore <paul@...l-moore.com>,
        Stephen Smalley <sds@...ho.nsa.gov>,
        Eric Paris <eparis@...isplace.org>,
        clang-built-linux@...glegroups.com,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        selinux@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] selinux: avoid uninitialized variable warning

On Fri, Mar 22, 2019 at 03:14:10PM +0100, Arnd Bergmann wrote:
> clang correctly points out a code path that would lead
> to an uninitialized variable use:
> 
> security/selinux/netlabel.c:310:6: error: variable 'addr' is used uninitialized whenever 'if' condition is false
>       [-Werror,-Wsometimes-uninitialized]
>         if (ip_hdr(skb)->version == 4) {
>             ^~~~~~~~~~~~~~~~~~~~~~~~~
> security/selinux/netlabel.c:322:40: note: uninitialized use occurs here
>         rc = netlbl_conn_setattr(ep->base.sk, addr, &secattr);
>                                               ^~~~
> security/selinux/netlabel.c:310:2: note: remove the 'if' if its condition is always true
>         if (ip_hdr(skb)->version == 4) {
>         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> security/selinux/netlabel.c:291:23: note: initialize the variable 'addr' to silence this warning
>         struct sockaddr *addr;
>                              ^
>                               = NULL
> 1 error generated.
> 
> This is probably harmless since we should not see ipv6 packets
> of CONFIG_IPV6 is disabled, but it's better to rearrange the code
> so this cannot happen.
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

Reviewed-by: Nathan Chancellor <natechancellor@...il.com>

> ---
>  security/selinux/netlabel.c | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/security/selinux/netlabel.c b/security/selinux/netlabel.c
> index 186e727b737b..d0e549d4f486 100644
> --- a/security/selinux/netlabel.c
> +++ b/security/selinux/netlabel.c
> @@ -288,7 +288,6 @@ int selinux_netlbl_sctp_assoc_request(struct sctp_endpoint *ep,
>  	int rc;
>  	struct netlbl_lsm_secattr secattr;
>  	struct sk_security_struct *sksec = ep->base.sk->sk_security;
> -	struct sockaddr *addr;
>  	struct sockaddr_in addr4;
>  #if IS_ENABLED(CONFIG_IPV6)
>  	struct sockaddr_in6 addr6;
> @@ -310,16 +309,15 @@ int selinux_netlbl_sctp_assoc_request(struct sctp_endpoint *ep,
>  	if (ip_hdr(skb)->version == 4) {
>  		addr4.sin_family = AF_INET;
>  		addr4.sin_addr.s_addr = ip_hdr(skb)->saddr;
> -		addr = (struct sockaddr *)&addr4;
> +		rc = netlbl_conn_setattr(ep->base.sk, (void*)&addr4, &secattr);
>  #if IS_ENABLED(CONFIG_IPV6)
>  	} else {
>  		addr6.sin6_family = AF_INET6;
>  		addr6.sin6_addr = ipv6_hdr(skb)->saddr;
> -		addr = (struct sockaddr *)&addr6;
> +		rc = netlbl_conn_setattr(ep->base.sk, (void*)&addr6, &secattr);
>  #endif
>  	}
>  
> -	rc = netlbl_conn_setattr(ep->base.sk, addr, &secattr);
>  	if (rc == 0)
>  		sksec->nlbl_state = NLBL_LABELED;
>  
> -- 
> 2.20.0
>