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SubjectRe: [PATCH BUGFIX -v2 -rc4] Smack: Respect 'unlabeled' netlabel mode

--- "Ahmed S. Darwish" <darwish.07@gmail.com> wrote:
> Hi!,
>
> [ Sorry, Fix: Acquire smack_ambient_lock before reading smack_net_ambient ]
>
> -->
>
> In case of Smack 'unlabeled' netlabel option, Smack passes a _zero_
> initialized 'secattr' to label a packet/sock. This causes an
> [unfound domain label error]/-ENOENT by netlbl_sock_setattr().
> Above Netlabel failure leads to Smack socket hooks failure causing
> an always-on socket() -EPERM error.
>
> Such packets should have a netlabel domain agreed with netlabel to
> represent unlabeled packets. Fortunately Smack net ambient label
> packets are agreed with netlabel to be treated as unlabeled packets.
>
> Treat all packets coming out from a 'unlabeled' Smack system as
> coming from the smack net ambient label.
>
> Signed-off-by: Ahmed S. Darwish <darwish.07@gmail.com>
> ---
>
> diff --git a/security/smack/smack.h b/security/smack/smack.h
> index 4a4477f..81b94ba 100644
> --- a/security/smack/smack.h
> +++ b/security/smack/smack.h
> @@ -16,6 +16,7 @@
> #include <linux/capability.h>
> #include <linux/spinlock.h>
> #include <linux/security.h>
> +#include <linux/mutex.h>
> #include <net/netlabel.h>
>
> /*
> @@ -178,6 +179,7 @@ u32 smack_to_secid(const char *);
> extern int smack_cipso_direct;
> extern int smack_net_nltype;
> extern char *smack_net_ambient;
> +extern struct mutex smack_ambient_lock;
>
> extern struct smack_known *smack_known;
> extern struct smack_known smack_known_floor;
> diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
> index b5c8f92..0d9c7dc 100644
> --- a/security/smack/smack_lsm.c
> +++ b/security/smack/smack_lsm.c
> @@ -1292,6 +1292,11 @@ static void smack_to_secattr(char *smack, struct
> netlbl_lsm_secattr *nlsp)
> }
> break;
> default:
> + mutex_lock(&smack_ambient_lock);
> + nlsp->domain = kstrdup(smack_net_ambient, GFP_ATOMIC);
> + mutex_unlock(&smack_ambient_lock);
> +
> + nlsp->flags = NETLBL_SECATTR_DOMAIN;
> break;
> }
> }

This is truely awful. I suggest that instead of doing this
locking you disallow changes to the ambient label if the
nltype is not a well handled type, that is, CIPSO. The overhead
you're introducing to handle a case that will cause the system
to be pretty well useless (if ambient isn't the floor label
your system isn't going to work very well) seems ill advised.

> diff --git a/security/smack/smackfs.c b/security/smack/smackfs.c
> index 271a835..cc357dc 100644
> --- a/security/smack/smackfs.c
> +++ b/security/smack/smackfs.c
> @@ -46,7 +46,7 @@ enum smk_inos {
> */
> static DEFINE_MUTEX(smack_list_lock);
> static DEFINE_MUTEX(smack_cipso_lock);
> -static DEFINE_MUTEX(smack_ambient_lock);
> +DEFINE_MUTEX(smack_ambient_lock);
>
> /*
> * This is the "ambient" label for network traffic.
>
> --
>
> "Better to light a candle, than curse the darkness"
>
> Ahmed S. Darwish
> Homepage: http://darwish.07.googlepages.com
> Blog: http://darwish-07.blogspot.com
>
>


Casey Schaufler
casey@schaufler-ca.com


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