Re: [PATCH] Smack: fix a dereference before null check on sock->sk

walter harms
2017-02-09T13:09:11Z

Am 09.02.2017 13:03, schrieb Colin King:
> From: Colin Ian King <colin.king@canonical.com>
>
> The initialisation of pointer ssp is from a dereference on sock->sk
> before sock-sk is null checked, hence there is a potential for a
> null pointer deference. Fix this by moving the assignment of ssp
> to just before it is used in the call to smk_ipv6_check.
>
> Detected with CoverityScan, CID#1324196 ("Dereference before null check")
>
> Signed-off-by: Colin Ian King <colin.king@canonical.com>
> ---
> security/smack/smack_lsm.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
> index fc8fb31..bb17387 100644
> --- a/security/smack/smack_lsm.c
> +++ b/security/smack/smack_lsm.c
> @@ -2899,7 +2899,7 @@ static int smack_socket_connect(struct socket *sock, struct sockaddr *sap,
> #endif
> #ifdef SMACK_IPV6_SECMARK_LABELING
> struct smack_known *rsp;
> - struct socket_smack *ssp = sock->sk->sk_security;
> + struct socket_smack *ssp;
> #endif
>
> if (sock->sk = NULL)
> @@ -2916,9 +2916,11 @@ static int smack_socket_connect(struct socket *sock, struct sockaddr *sap,
> return -EINVAL;
> #ifdef SMACK_IPV6_SECMARK_LABELING
> rsp = smack_ipv6host_label(sip);
> - if (rsp != NULL)
> + if (rsp != NULL) {
> + ssp = sock->sk->sk_security;
> rc = smk_ipv6_check(ssp->smk_out, rsp, sip,
> SMK_CONNECTING);
> + }
> #endif
> #ifdef SMACK_IPV6_PORT_LABELING
> rc = smk_ipv6_port_check(sock->sk, sip, SMK_CONNECTING);

In the hope of reducing the ifdef forrest:
you could move the struct smack_known *rsp; and struct socket_smack *ssp; into the block like:

{
struct smack_known *rsp=smack_ipv6host_label(sip);

if (rsp != NULL) {
struct socket_smack *ssp= sock->sk->sk_security;
rc = smk_ipv6_check(ssp->smk_out, rsp, sip,
SMK_CONNECTING);
}
}

just my 2 cents ...

re,
wh