On Fri, Mar 22, 2019 at 10:14 AM Arnd Bergmann <arnd@xxxxxxxx> 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@xxxxxxxx>
> ---
> security/selinux/netlabel.c | 6 ++----
> 1 file changed, 2 insertions(+), 4 deletions(-)
Hi Arnd,
Thanks for pointing this out and providing a fix. I think you're
right in that the should be pretty harmless, but I also agree that we
should fix it; some thoughts on the patch below ...
> 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
While we are hardening the code a bit, I'm thinking we should probably
refactor this if-else a bit, some pseudo code for example:
if (ip_hdr == 4) {
rc = netlbl_conn_setattr();
#if CONFIG_IPV6
} else if (ip_hdr == 6) {
rc = netlbl_conn_setattr();
#endif
} else {
rc = -EAFNOSUPPORT;
}
Thoughts?
> }
>
> - 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
