[v3] selinux: avoid uninitialized variable warning

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

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.

Link: https://lore.kernel.org/patchwork/patch/1053663/
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

---
v3: add missing ip_hdr(skb)->version == 6 check
v2: revise after discussing with Paul Moore
---
 security/selinux/netlabel.c | 14 +++++---------
 1 file changed, 5 insertions(+), 9 deletions(-)

-- 
2.20.0

On Mon, Mar 25, 2019 at 10:23 AM Arnd Bergmann <arnd@arndb.de> 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

>

> 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.

>

> Link: https://lore.kernel.org/patchwork/patch/1053663/

> Signed-off-by: Arnd Bergmann <arnd@arndb.de>

> ---

> v3: add missing ip_hdr(skb)->version == 6 check

> v2: revise after discussing with Paul Moore

> ---

>  security/selinux/netlabel.c | 14 +++++---------

>  1 file changed, 5 insertions(+), 9 deletions(-)


Better, thank you; merged into selinux/next.  FYI, I had to fix a
couple of style errors that checkpatch.pl was complaining about ("void
*" not "void*").

> diff --git a/security/selinux/netlabel.c b/security/selinux/netlabel.c

> index 186e727b737b..f10813e54d07 100644

> --- a/security/selinux/netlabel.c

> +++ b/security/selinux/netlabel.c

> @@ -288,11 +288,8 @@ 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;

> -#endif

>

>         if (ep->base.sk->sk_family != PF_INET &&

>                                 ep->base.sk->sk_family != PF_INET6)

> @@ -310,16 +307,15 @@ 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;

> -#if IS_ENABLED(CONFIG_IPV6)

> -       } else {

> +               rc = netlbl_conn_setattr(ep->base.sk, (void*)&addr4, &secattr);

> +       } else if (IS_ENABLED(CONFIG_IPV6) && ip_hdr(skb)->version == 6) {

>                 addr6.sin6_family = AF_INET6;

>                 addr6.sin6_addr = ipv6_hdr(skb)->saddr;

> -               addr = (struct sockaddr *)&addr6;

> -#endif

> +               rc = netlbl_conn_setattr(ep->base.sk, (void*)&addr6, &secattr);

> +       } else {

> +               rc = -EAFNOSUPPORT;

>         }

>

> -       rc = netlbl_conn_setattr(ep->base.sk, addr, &secattr);

>         if (rc == 0)

>                 sksec->nlbl_state = NLBL_LABELED;

>

> --

> 2.20.0


-- 
paul moore
www.paul-moore.com