linux-kernel - [RFC PATCH 5/7] audit: allow audit_cmd

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

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Thu, 22 Oct 2015 14:53:18 -0400
From:	Richard Guy Briggs <rgb@...hat.com>
To:	linux-audit@...hat.com, linux-kernel@...r.kernel.org
Cc:	Richard Guy Briggs <rgb@...hat.com>, sgrubb@...hat.com,
	pmoore@...hat.com, eparis@...hat.com, v.rathor@...il.com,
	ctcard@...mail.com
Subject: [RFC PATCH 5/7] audit: allow audit_cmd_mutex holders to use reserves

If we hold the audit_cmd_mutex, we should never sleep waiting for auditd
to drain the queue since auditd may need the mutex to shut down.

This was first implemented with mutex_trylock(), but since
audit_log_start() can be called in softirq context, that won't work.
Next, owner_running() was used to check audit_cmd_mutex but another
process could have this locked on another cpu.  Use rcu_read_lock() and
ACCESS_ONCE() to check audit_cmd_mutex.

Signed-off-by: Richard Guy Briggs <rgb@...hat.com>
---
 kernel/audit.c |    7 +++++--
 1 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/kernel/audit.c b/kernel/audit.c
index 02a5ec0..34411af 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -1376,12 +1376,15 @@ struct audit_buffer *audit_log_start(struct audit_context *ctx, gfp_t gfp_mask,
 		return NULL;
 
 	if (gfp_mask & __GFP_WAIT) {
-		if (current->tgid == 1 || (audit_pid && audit_pid == current->tgid))
+		rcu_read_lock();
+		if (ACCESS_ONCE(audit_cmd_mutex.owner) == current ||
+		    current->tgid == 1 ||
+		    (audit_pid && audit_pid == current->tgid))
 			gfp_mask &= ~__GFP_WAIT;
 		else
 			reserve = 0;
+		rcu_read_unlock();
 	}
-
 	while (audit_backlog_limit
 	       && skb_queue_len(&audit_skb_queue) > audit_backlog_limit + reserve) {
 		if (gfp_mask & __GFP_WAIT && audit_backlog_wait_time) {
-- 
1.7.1

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/