| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Date: Mon, 12 Dec 2016 12:10:23 -0500
From: Paul Moore <paul@...l-moore.com>
To: Richard Guy Briggs <rgb@...hat.com>
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-audit@...hat.com, edumazet@...gle.com,
xiyou.wangcong@...il.com, dvyukov@...gle.com
Subject: Re: [PATCH v2] audit: use proper refcount locking on audit_sock
On Mon, Dec 12, 2016 at 5:03 AM, Richard Guy Briggs <rgb@...hat.com> wrote:
> Resetting audit_sock appears to be racy.
>
> audit_sock was being copied and dereferenced without using a refcount on
> the source sock.
>
> Bump the refcount on the underlying sock when we store a refrence in
> audit_sock and release it when we reset audit_sock. audit_sock
> modification needs the audit_cmd_mutex.
>
> See: https://lkml.org/lkml/2016/11/26/232
>
> Thanks to Eric Dumazet <edumazet@...gle.com> and Cong Wang
> <xiyou.wangcong@...il.com> on ideas how to fix it.
>
> Signed-off-by: Richard Guy Briggs <rgb@...hat.com>
> ---
> There has been a lot of change in the audit code that is about to go
> upstream to address audit queue issues. This patch is based on the
> source tree: git://git.infradead.org/users/pcmoore/audit#next
> ---
> kernel/audit.c | 34 ++++++++++++++++++++++++++++------
> 1 files changed, 28 insertions(+), 6 deletions(-)
This is coming in pretty late for the v4.10 merge window, much later
than I would usually take things, but this is arguably important, and
(at first glance) relatively low risk - what testing have you done on
this?
> diff --git a/kernel/audit.c b/kernel/audit.c
> index f20eee0..439f7f3 100644
> --- a/kernel/audit.c
> +++ b/kernel/audit.c
> @@ -452,7 +452,9 @@ static void auditd_reset(void)
> struct sk_buff *skb;
>
> /* break the connection */
> + sock_put(audit_sock);
> audit_pid = 0;
> + audit_nlk_portid = 0;
> audit_sock = NULL;
>
> /* flush all of the retry queue to the hold queue */
> @@ -478,6 +480,12 @@ static int kauditd_send_unicast_skb(struct sk_buff *skb)
> if (rc >= 0) {
> consume_skb(skb);
> rc = 0;
> + } else {
> + if (rc & (-ENOMEM|-EPERM|-ECONNREFUSED)) {
> + mutex_lock(&audit_cmd_mutex);
> + auditd_reset();
> + mutex_unlock(&audit_cmd_mutex);
> + }
> }
>
> return rc;
> @@ -579,7 +587,9 @@ static int kauditd_thread(void *dummy)
>
> auditd = 0;
> if (AUDITD_BAD(rc, reschedule)) {
> + mutex_lock(&audit_cmd_mutex);
> auditd_reset();
> + mutex_unlock(&audit_cmd_mutex);
> reschedule = 0;
> }
> } else
> @@ -594,7 +604,9 @@ static int kauditd_thread(void *dummy)
> auditd = 0;
> if (AUDITD_BAD(rc, reschedule)) {
> kauditd_hold_skb(skb);
> + mutex_lock(&audit_cmd_mutex);
> auditd_reset();
> + mutex_unlock(&audit_cmd_mutex);
> reschedule = 0;
> } else
> /* temporary problem (we hope), queue
> @@ -623,7 +635,9 @@ quick_loop:
> if (rc) {
> auditd = 0;
> if (AUDITD_BAD(rc, reschedule)) {
> + mutex_lock(&audit_cmd_mutex);
> auditd_reset();
> + mutex_unlock(&audit_cmd_mutex);
> reschedule = 0;
> }
>
> @@ -1004,17 +1018,22 @@ static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
> return -EACCES;
> }
> if (audit_pid && new_pid &&
> - audit_replace(requesting_pid) != -ECONNREFUSED) {
> + (audit_replace(requesting_pid) & (-ECONNREFUSED|-EPERM|-ENOMEM))) {
> audit_log_config_change("audit_pid", new_pid, audit_pid, 0);
> return -EEXIST;
> }
> if (audit_enabled != AUDIT_OFF)
> audit_log_config_change("audit_pid", new_pid, audit_pid, 1);
> - audit_pid = new_pid;
> - audit_nlk_portid = NETLINK_CB(skb).portid;
> - audit_sock = skb->sk;
> - if (!new_pid)
> + if (new_pid) {
> + if (audit_sock)
> + sock_put(audit_sock);
> + audit_pid = new_pid;
> + audit_nlk_portid = NETLINK_CB(skb).portid;
> + sock_hold(skb->sk);
> + audit_sock = skb->sk;
> + } else {
> auditd_reset();
> + }
> wake_up_interruptible(&kauditd_wait);
> }
> if (s.mask & AUDIT_STATUS_RATE_LIMIT) {
> @@ -1283,8 +1302,11 @@ static void __net_exit audit_net_exit(struct net *net)
> {
> struct audit_net *aunet = net_generic(net, audit_net_id);
> struct sock *sock = aunet->nlsk;
> - if (sock == audit_sock)
> + if (sock == audit_sock) {
> + mutex_lock(&audit_cmd_mutex);
> auditd_reset();
> + mutex_unlock(&audit_cmd_mutex);
> + }
>
> RCU_INIT_POINTER(aunet->nlsk, NULL);
> synchronize_net();
> --
> 1.7.1
>
> --
> Linux-audit mailing list
> Linux-audit@...hat.com
> https://www.redhat.com/mailman/listinfo/linux-audit
--
paul moore
www.paul-moore.com
Powered by blists - more mailing lists