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Date: Thu, 25 Jul 2013 13:00:34 +0900
From: Kyungmin Park <kmpark@...radead.org>
To: Casey Schaufler <casey@...aufler-ca.com>
Cc: LSM <linux-security-module@...r.kernel.org>,
LKLM <linux-kernel@...r.kernel.org>,
Linus Torvalds <torvalds@...ux-foundation.org>,
James Morris <jmorris@...ei.org>
Subject: Re: [PATCH] Smack: IPv6 casting error fix
On Thu, Jul 25, 2013 at 9:49 AM, Casey Schaufler <casey@...aufler-ca.com> wrote:
> Subject: [PATCH] Smack: IPv6 casting error fix
>
> The original implementation of the Smack IPv6 port based
> local controls works most of the time using a sockaddr as
> a temporary variable, but not always as it overflows in
> some circumstances. The correct data is a sockaddr_in6.
> A struct sockaddr isn't as large as a struct sockaddr_in6.
> There would need to be casting one way or the other. This
> patch gets it the right way.
>
> This problem required some effort to make occur in development
> with 3.10, but hits every time in 3.11. This patch should go
> into 3.11.
>
> Signed-off-by: Casey Schaufler <casey@...aufler-ca.com>
>
> ---
> security/smack/smack_lsm.c | 24 +++++++++++-------------
> 1 files changed, 11 insertions(+), 13 deletions(-)
>
> diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
> index 3f7682a..eefbd10 100644
> --- a/security/smack/smack_lsm.c
> +++ b/security/smack/smack_lsm.c
> @@ -1998,12 +1998,11 @@ static void smk_ipv6_port_label(struct socket *sock, struct sockaddr *address)
> *
> * Create or update the port list entry
> */
> -static int smk_ipv6_port_check(struct sock *sk, struct sockaddr *address,
> +static int smk_ipv6_port_check(struct sock *sk, struct sockaddr_in6 *address,
> int act)
> {
> __be16 *bep;
> __be32 *be32p;
> - struct sockaddr_in6 *addr6;
> struct smk_port_label *spp;
> struct socket_smack *ssp = sk->sk_security;
> struct smack_known *skp;
> @@ -2025,10 +2024,9 @@ static int smk_ipv6_port_check(struct sock *sk, struct sockaddr *address,
> /*
> * Get the IP address and port from the address.
> */
> - addr6 = (struct sockaddr_in6 *)address;
> - port = ntohs(addr6->sin6_port);
> - bep = (__be16 *)(&addr6->sin6_addr);
> - be32p = (__be32 *)(&addr6->sin6_addr);
> + port = ntohs(address->sin6_port);
> + bep = (__be16 *)(&address->sin6_addr);
> + be32p = (__be32 *)(&address->sin6_addr);
>
> /*
> * It's remote, so port lookup does no good.
> @@ -2060,9 +2058,9 @@ auditout:
> ad.a.u.net->family = sk->sk_family;
> ad.a.u.net->dport = port;
> if (act == SMK_RECEIVING)
> - ad.a.u.net->v6info.saddr = addr6->sin6_addr;
> + ad.a.u.net->v6info.saddr = address->sin6_addr;
> else
> - ad.a.u.net->v6info.daddr = addr6->sin6_addr;
> + ad.a.u.net->v6info.daddr = address->sin6_addr;
> #endif
> return smk_access(skp, object, MAY_WRITE, &ad);
> }
> @@ -2201,7 +2199,8 @@ static int smack_socket_connect(struct socket *sock, struct sockaddr *sap,
> case PF_INET6:
> if (addrlen < sizeof(struct sockaddr_in6))
> return -EINVAL;
> - rc = smk_ipv6_port_check(sock->sk, sap, SMK_CONNECTING);
> + rc = smk_ipv6_port_check(sock->sk, (struct sockaddr_in6 *)sap,
I reviewed ipv4 and ipv6 codes at smack. the variable 'sap' is used
for both 'struct sockaddr' and 'struct sockaddr_in6'.
It's very confusing to know what's the exact usage. so I suggest to
use separate variable for each cases.
as you know, the sizeof(struct sockaddr_in6) is bigger than
sizeof(struct sockaddr). now it valid cast it as above.
but other case it corrupts the stack.
> + SMK_CONNECTING);
> break;
> }
> return rc;
> @@ -3034,7 +3033,7 @@ static int smack_socket_sendmsg(struct socket *sock, struct msghdr *msg,
> int size)
> {
> struct sockaddr_in *sip = (struct sockaddr_in *) msg->msg_name;
> - struct sockaddr *sap = (struct sockaddr *) msg->msg_name;
> + struct sockaddr_in6 *sap = (struct sockaddr_in6 *) msg->msg_name;
sap is used for struct sockaddr_in6.
> int rc = 0;
>
> /*
> @@ -3121,9 +3120,8 @@ static struct smack_known *smack_from_secattr(struct netlbl_lsm_secattr *sap,
> return smack_net_ambient;
> }
>
> -static int smk_skb_to_addr_ipv6(struct sk_buff *skb, struct sockaddr *sap)
> +static int smk_skb_to_addr_ipv6(struct sk_buff *skb, struct sockaddr_in6 *sip)
'sip' is used for struct sockaddr_in6.
> {
> - struct sockaddr_in6 *sip = (struct sockaddr_in6 *)sap;
> u8 nexthdr;
> int offset;
> int proto = -EINVAL;
> @@ -3181,7 +3179,7 @@ static int smack_socket_sock_rcv_skb(struct sock *sk, struct sk_buff *skb)
> struct netlbl_lsm_secattr secattr;
> struct socket_smack *ssp = sk->sk_security;
> struct smack_known *skp;
> - struct sockaddr sadd;
> + struct sockaddr_in6 sadd;
'sadd' is used for struct sockaddr_in6.
Thank you,
Kyungmin Park
> int rc = 0;
> struct smk_audit_info ad;
> #ifdef CONFIG_AUDIT
>
> --
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