linux-kernel - [PATCH][RESEND 2] Revert "AUDIT: Allow login in non-init namespaces"

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Message-ID: <20150109014448.GF27996@mail.thefacebook.com>
Date:	Thu, 8 Jan 2015 17:44:48 -0800
From:	Calvin Owens <calvinowens@...com>
To:	Eric Paris <eparis@...hat.com>, <rgb@...hat.com>,
	<ebiederm@...ssion.com>, <paul@...l-moore.com>
CC:	<linux-kernel@...r.kernel.org>, <kernel-team@...com>,
	<stable@...r.kernel.org>, <linux-audit@...hat.com>
Subject: [PATCH][RESEND 2] Revert "AUDIT: Allow login in non-init namespaces"

This reverts 543bc6a1a987 "AUDIT: Allow login in non-init namespaces".

This commit incorrectly assumes that libpam treats -ECONNREFUSED as
an indicator that audit is disabled, and -EPERM or any other error
as a fatal error that prevents the login from continuing.

The opposite is in fact true: -EPERM allows the login to continue,
and -ECONNREFUSED causes it to refuse the login. This behavior has
been unchanged in upstream linux-pam since at least 2008.

Reverting this change allows libpam to again work as expected in
non-init user namespaces.

Signed-off-by: Calvin Owens <calvinowens@...com>
Cc: stable@...r.kernel.org
---
Relevant code in linux-pam:
https://git.fedorahosted.org/cgit/linux-pam.git/tree/libpam/pam_audit.c#n56

 kernel/audit.c | 12 +-----------
 1 file changed, 1 insertion(+), 11 deletions(-)

diff --git a/kernel/audit.c b/kernel/audit.c
index 80983df..656e8ce 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -640,18 +640,8 @@ static int audit_netlink_ok(struct sk_buff *skb, u16 msg_type)
 	int err = 0;
 
 	/* Only support initial user namespace for now. */
-	/*
-	 * We return ECONNREFUSED because it tricks userspace into thinking
-	 * that audit was not configured into the kernel.  Lots of users
-	 * configure their PAM stack (because that's what the distro does)
-	 * to reject login if unable to send messages to audit.  If we return
-	 * ECONNREFUSED the PAM stack thinks the kernel does not have audit
-	 * configured in and will let login proceed.  If we return EPERM
-	 * userspace will reject all logins.  This should be removed when we
-	 * support non init namespaces!!
-	 */
 	if (current_user_ns() != &init_user_ns)
-		return -ECONNREFUSED;
+		return -EPERM;
 
 	switch (msg_type) {
 	case AUDIT_LIST:
-- 
2.1.1
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