From 4b3e4ed6b0d958d7fb2f160bb8ebfb4f0db19382 Mon Sep 17 00:00:00 2001 From: Richard Guy Briggs Date: Thu, 20 Apr 2017 13:07:30 -0400 Subject: audit: unswing cap_* fields in PATH records The cap_* fields swing in and out of PATH records. If no capabilities are set, the cap_* fields are completely missing and when one of the cap_fi or cap_fp values is empty, that field is omitted. Original: type=PATH msg=audit(04/20/2017 12:17:11.222:193) : item=1 name=/lib64/ld-linux-x86-64.so.2 inode=787694 dev=08:03 mode=file,755 ouid=root ogid=root rdev=00:00 obj=system_u:object_r:ld_so_t:s0 nametype=NORMAL type=PATH msg=audit(04/20/2017 12:17:11.222:193) : item=0 name=/home/sleep inode=1319469 dev=08:03 mode=file,suid,755 ouid=root ogid=root rdev=00:00 obj=system_u:object_r:bin_t:s0 nametype=NORMAL cap_fp=sys_admin cap_fe=1 cap_fver=2 Normalize the PATH record by always printing all 4 cap_* fields. Fixed: type=PATH msg=audit(04/20/2017 13:01:31.679:201) : item=1 name=/lib64/ld-linux-x86-64.so.2 inode=787694 dev=08:03 mode=file,755 ouid=root ogid=root rdev=00:00 obj=system_u:object_r:ld_so_t:s0 nametype=NORMAL cap_fp=none cap_fi=none cap_fe=0 cap_fver=0 type=PATH msg=audit(04/20/2017 13:01:31.679:201) : item=0 name=/home/sleep inode=1319469 dev=08:03 mode=file,suid,755 ouid=root ogid=root rdev=00:00 obj=system_u:object_r:bin_t:s0 nametype=NORMAL cap_fp=sys_admin cap_fi=none cap_fe=1 cap_fver=2 See: https://github.com/linux-audit/audit-kernel/issues/42 Signed-off-by: Richard Guy Briggs Signed-off-by: Paul Moore --- kernel/audit.c | 20 ++++---------------- 1 file changed, 4 insertions(+), 16 deletions(-) (limited to 'kernel/audit.c') diff --git a/kernel/audit.c b/kernel/audit.c index a7c6a50477aa..b2e877100242 100644 --- a/kernel/audit.c +++ b/kernel/audit.c @@ -1999,22 +1999,10 @@ void audit_log_cap(struct audit_buffer *ab, char *prefix, kernel_cap_t *cap) static void audit_log_fcaps(struct audit_buffer *ab, struct audit_names *name) { - kernel_cap_t *perm = &name->fcap.permitted; - kernel_cap_t *inh = &name->fcap.inheritable; - int log = 0; - - if (!cap_isclear(*perm)) { - audit_log_cap(ab, "cap_fp", perm); - log = 1; - } - if (!cap_isclear(*inh)) { - audit_log_cap(ab, "cap_fi", inh); - log = 1; - } - - if (log) - audit_log_format(ab, " cap_fe=%d cap_fver=%x", - name->fcap.fE, name->fcap_ver); + audit_log_cap(ab, "cap_fp", &name->fcap.permitted); + audit_log_cap(ab, "cap_fi", &name->fcap.inheritable); + audit_log_format(ab, " cap_fe=%d cap_fver=%x", + name->fcap.fE, name->fcap_ver); } static inline int audit_copy_fcaps(struct audit_names *name, -- cgit v1.2.3-55-g7522 From c81be52a3ac0267aa830a2c4cb769030ea3483c9 Mon Sep 17 00:00:00 2001 From: Paul Moore Date: Mon, 12 Jun 2017 09:35:24 -0400 Subject: audit: fix a race condition with the auditd tracking code Originally reported by Adam and Dusty, it appears we have a small race window in kauditd_thread(), as documented in the Fedora BZ: * https://bugzilla.redhat.com/show_bug.cgi?id=1459326#c35 "This issue is partly due to the read-copy nature of RCU, and partly due to how we sync the auditd_connection state across kauditd_thread and the audit control channel. The kauditd_thread thread is always running so it can service the record queues and emit the multicast messages, if it happens to be just past the "main_queue" label, but before the "if (sk == NULL || ...)" if-statement which calls auditd_reset() when the new auditd connection is registered it could end up resetting the auditd connection, regardless of if it is valid or not. This is a rather small window and the variable nature of multi-core scheduling explains why this is proving rather difficult to reproduce." The fix is to have functions only call auditd_reset() when they believe that the kernel/auditd connection is still valid, e.g. non-NULL, and to have these callers pass their local copy of the auditd_connection pointer to auditd_reset() where it can be compared with the current connection state before resetting. If the caller has a stale state tracking pointer then the reset is ignored. We also make a small change to kauditd_thread() so that if the kernel/auditd connection is dead we skip the retry queue and send the records straight to the hold queue. This is necessary as we used to rely on auditd_reset() to occasionally purge the retry queue but we are going to be calling the reset function much less now and we want to make sure the retry queue doesn't grow unbounded. Reported-by: Adam Williamson Reported-by: Dusty Mabe Reviewed-by: Richard Guy Briggs Signed-off-by: Paul Moore --- kernel/audit.c | 36 +++++++++++++++++++++++------------- 1 file changed, 23 insertions(+), 13 deletions(-) (limited to 'kernel/audit.c') diff --git a/kernel/audit.c b/kernel/audit.c index b2e877100242..e1e2b3abfb93 100644 --- a/kernel/audit.c +++ b/kernel/audit.c @@ -575,12 +575,16 @@ static void kauditd_retry_skb(struct sk_buff *skb) /** * auditd_reset - Disconnect the auditd connection + * @ac: auditd connection state * * Description: * Break the auditd/kauditd connection and move all the queued records into the - * hold queue in case auditd reconnects. + * hold queue in case auditd reconnects. It is important to note that the @ac + * pointer should never be dereferenced inside this function as it may be NULL + * or invalid, you can only compare the memory address! If @ac is NULL then + * the connection will always be reset. */ -static void auditd_reset(void) +static void auditd_reset(const struct auditd_connection *ac) { unsigned long flags; struct sk_buff *skb; @@ -590,6 +594,11 @@ static void auditd_reset(void) spin_lock_irqsave(&auditd_conn_lock, flags); ac_old = rcu_dereference_protected(auditd_conn, lockdep_is_held(&auditd_conn_lock)); + if (ac && ac != ac_old) { + /* someone already registered a new auditd connection */ + spin_unlock_irqrestore(&auditd_conn_lock, flags); + return; + } rcu_assign_pointer(auditd_conn, NULL); spin_unlock_irqrestore(&auditd_conn_lock, flags); @@ -649,8 +658,8 @@ static int auditd_send_unicast_skb(struct sk_buff *skb) return rc; err: - if (rc == -ECONNREFUSED) - auditd_reset(); + if (ac && rc == -ECONNREFUSED) + auditd_reset(ac); return rc; } @@ -795,9 +804,9 @@ static int kauditd_thread(void *dummy) rc = kauditd_send_queue(sk, portid, &audit_hold_queue, UNICAST_RETRIES, NULL, kauditd_rehold_skb); - if (rc < 0) { + if (ac && rc < 0) { sk = NULL; - auditd_reset(); + auditd_reset(ac); goto main_queue; } @@ -805,9 +814,9 @@ static int kauditd_thread(void *dummy) rc = kauditd_send_queue(sk, portid, &audit_retry_queue, UNICAST_RETRIES, NULL, kauditd_hold_skb); - if (rc < 0) { + if (ac && rc < 0) { sk = NULL; - auditd_reset(); + auditd_reset(ac); goto main_queue; } @@ -815,12 +824,13 @@ main_queue: /* process the main queue - do the multicast send and attempt * unicast, dump failed record sends to the retry queue; if * sk == NULL due to previous failures we will just do the - * multicast send and move the record to the retry queue */ + * multicast send and move the record to the hold queue */ rc = kauditd_send_queue(sk, portid, &audit_queue, 1, kauditd_send_multicast_skb, - kauditd_retry_skb); - if (sk == NULL || rc < 0) - auditd_reset(); + (sk ? + kauditd_retry_skb : kauditd_hold_skb)); + if (ac && rc < 0) + auditd_reset(ac); sk = NULL; /* drop our netns reference, no auditd sends past this line */ @@ -1230,7 +1240,7 @@ static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh) auditd_pid, 1); /* unregister the auditd connection */ - auditd_reset(); + auditd_reset(NULL); } } if (s.mask & AUDIT_STATUS_RATE_LIMIT) { -- cgit v1.2.3-55-g7522 From cd33f5f2cbfaadc21270f3ddac7c3c33e0a1a28c Mon Sep 17 00:00:00 2001 From: Paul Moore Date: Mon, 12 Jun 2017 11:53:09 -0400 Subject: audit: make sure we never skip the multicast broadcast When the auditd connection is reset, either intentionally or due to a failure, any records that were in the main backlog queue would not be sent in a multicast broadcast. This patch fixes this problem by not flushing the main backlog queue on a connection reset, the main kauditd_thread() will take care of that normally. Resolves: https://github.com/linux-audit/audit-kernel/issues/41 Reviewed-by: Richard Guy Briggs Signed-off-by: Paul Moore --- kernel/audit.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) (limited to 'kernel/audit.c') diff --git a/kernel/audit.c b/kernel/audit.c index e1e2b3abfb93..7cad70214b81 100644 --- a/kernel/audit.c +++ b/kernel/audit.c @@ -605,11 +605,10 @@ static void auditd_reset(const struct auditd_connection *ac) if (ac_old) call_rcu(&ac_old->rcu, auditd_conn_free); - /* flush all of the main and retry queues to the hold queue */ + /* flush the retry queue to the hold queue, but don't touch the main + * queue since we need to process that normally for multicast */ while ((skb = skb_dequeue(&audit_retry_queue))) kauditd_hold_skb(skb); - while ((skb = skb_dequeue(&audit_queue))) - kauditd_hold_skb(skb); } /** -- cgit v1.2.3-55-g7522