[PATCH] audit: printk USER_AVC messages when audit isn't enabled
Richard Guy Briggs
rgb at redhat.com
Tue Aug 20 14:45:48 UTC 2013
On Thu, Jul 25, 2013 at 06:02:55PM -0700, Tyler Hicks wrote:
> When the audit=1 kernel parameter is absent and auditd is not running,
> AUDIT_USER_AVC messages are being silently discarded.
>
> AUDIT_USER_AVC messages should be sent to userspace using printk(), as
> mentioned in the commit message of
> 4a4cd633b575609b741a1de7837223a2d9e1c34c ("AUDIT: Optimise the
> audit-disabled case for discarding user messages").
>
> When audit_enabled is 0, audit_receive_msg() discards all user messages
> except for AUDIT_USER_AVC messages. However, audit_log_common_recv_msg()
> refuses to allocate an audit_buffer if audit_enabled is 0. The fix is to
> special case AUDIT_USER_AVC messages in both functions.
>
> Signed-off-by: Tyler Hicks <tyhicks at canonical.com>
> Cc: Al Viro <viro at zeniv.linux.org.uk>
> Cc: Eric Paris <eparis at redhat.com>
> Cc: linux-audit at redhat.com
> ---
>
> It looks like commit 50397bd1e471391d27f64efad9271459c913de87 ("[AUDIT] clean
> up audit_receive_msg()") introduced this bug, so I think that this patch should
> also get the tag:
>
> Cc: <stable at kernel.org> # v2.6.25+
>
> Al and Eric, I'll leave that up to you two.
Hi Tyler,
This patch looks entirely reasonable to me.
Acked-by: Richard Guy Briggs <rbriggs at redhat.com>
> Here's my test matrix showing where messages end up as a result of a call to
> libaudit's audit_log_user_avc_message():
>
> | unpatched patched
> ----------------+--------------------------------
> w/o audit=1 & | *dropped* syslog
> w/o auditd |
> |
> w/ audit=1 & | syslog syslog
> w/o auditd |
> |
> w/o audit=1 & | audit.log audit.log
> w/ auditd |
> |
> w/ audit=1 & | audit.log audit.log
> w/ auditd |
>
> Thanks!
>
> kernel/audit.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/audit.c b/kernel/audit.c
> index 91e53d0..f4f2773 100644
> --- a/kernel/audit.c
> +++ b/kernel/audit.c
> @@ -613,7 +613,7 @@ static int audit_log_common_recv_msg(struct audit_buffer **ab, u16 msg_type)
> int rc = 0;
> uid_t uid = from_kuid(&init_user_ns, current_uid());
>
> - if (!audit_enabled) {
> + if (!audit_enabled && msg_type != AUDIT_USER_AVC) {
> *ab = NULL;
> return rc;
> }
> --
> 1.8.3.2
>
> --
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> Linux-audit at redhat.com
> https://www.redhat.com/mailman/listinfo/linux-audit
- RGB
--
Richard Guy Briggs <rbriggs at redhat.com>
Senior Software Engineer
Kernel Security
AMER ENG Base Operating Systems
Remote, Ottawa, Canada
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