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 <eduma...@google.com> and Cong Wang <xiyou.wangc...@gmail.com> on ideas how to fix it. Signed-off-by: Richard Guy Briggs <r...@redhat.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 | 28 +++++++++++++++++++++++----- 1 files changed, 23 insertions(+), 5 deletions(-) diff --git a/kernel/audit.c b/kernel/audit.c index f20eee0..3bb4126 100644 --- a/kernel/audit.c +++ b/kernel/audit.c @@ -446,14 +446,19 @@ static void kauditd_retry_skb(struct sk_buff *skb) * Description: * Break the auditd/kauditd connection and move all the records in the retry * queue into the hold queue in case auditd reconnects. + * The audit_cmd_mutex must be held when calling this function. */ static void auditd_reset(void) { struct sk_buff *skb; /* break the connection */ + if (audit_sock) { + sock_put(audit_sock); + audit_sock = NULL; + } audit_pid = 0; - audit_sock = NULL; + audit_nlk_portid = 0; /* flush all of the retry queue to the hold queue */ while ((skb = skb_dequeue(&audit_retry_queue))) @@ -579,7 +584,9 @@ 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 +601,9 @@ 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 +632,9 @@ 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; } @@ -1010,11 +1021,16 @@ static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh) } 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 +1299,10 @@ 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; + mutex_lock(&audit_cmd_mutex); if (sock == audit_sock) auditd_reset(); + mutex_unlock(&audit_cmd_mutex); RCU_INIT_POINTER(aunet->nlsk, NULL); synchronize_net(); -- 1.7.1
