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Message-ID: <20131209202157.GC1687@madcap2.tricolour.ca>
Date: Mon, 9 Dec 2013 15:21:57 -0500
From: Richard Guy Briggs <rgb@...hat.com>
To: Eric Paris <eparis@...hat.com>
Cc: linux-audit@...hat.com, linux-kernel@...r.kernel.org,
Steve Grubb <sgrubb@...hat.com>
Subject: Re: [PATCH] audit: process errors from filter user rules
On 13/12/05, Eric Paris wrote:
> I know we talked about this patch, and it seemed like a good idea at the
> time, but honestly, these races are so rare, it isn't worth the code
> complexity. I tried to simplify the readability of your code and got
> something better, but still the loop is needless...
Your original code suggestion was cleaner and simpler than mine, but I
tried to code it in a structured manner without gotos, perhaps naively
believing structured code to be superior. I think that effort backfired
and made it more complex. I'm ok going back to your original ideas.
I do still think that retry and passing back of error codes is the
better approach.
> Just log the messages on any error, even with a dontaudit rule... How
> about a function like:
I suspect this isn't what you intended. The way this is written, it
always breaks after the first rule, not checking any of the others.
> int audit_filter_user(int type)
> {
> enum audit_state state = AUDIT_DISABLED;
> struct audit_entry *e;
> int rc, ret;
>
> ret = 1; /* Audit by default */
>
> rcu_read_lock();
> list_for_each_entry_rcu(e, &audit_filter_list[AUDIT_FILTER_USER], list) {
> rc = audit_filter_user_rules(&e->rule, type, &state);
> if (rc > 0 && state == AUDIT_DISABLED)
> ret = 0;
> break;
> }
> rcu_read_unlock();
> return ret;
> }
Did you mean?
list_for_each_entry_rcu(e, &audit_filter_list[AUDIT_FILTER_USER], list) {
rc = audit_filter_user_rules(&e->rule, type, &state);
if (rc) {
if (rc > 0 && state == AUDIT_DISABLED)
ret = 0;
break;
}
}
> and use some sense with the 80 character line length rule. It's 81
> long. Just let it be long even if checkpatch whines....
Yeah, I haven't been too pedantic about line length warnings barely over
80 characters when it affects readability...
> -Eric
>
> On Wed, 2013-12-04 at 22:45 -0500, Richard Guy Briggs wrote:
> > Errors from filter user rules were previously ignored, and worse, an error on
> > a AUDIT_NEVER rule disabled logging on that rule. On -ESTALE, retry up to 5
> > times. On error on AUDIT_NEVER rules, log.
> >
> > Signed-off-by: Richard Guy Briggs <rgb@...hat.com>
> > ---
> > kernel/audit.c | 2 +-
> > kernel/auditfilter.c | 44 +++++++++++++++++++++++++++++++-------------
> > 2 files changed, 32 insertions(+), 14 deletions(-)
> >
> > diff --git a/kernel/audit.c b/kernel/audit.c
> > index 4cbc945..c93cf06 100644
> > --- a/kernel/audit.c
> > +++ b/kernel/audit.c
> > @@ -706,7 +706,7 @@ static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
> > return 0;
> >
> > err = audit_filter_user(msg_type);
> > - if (err == 1) {
> > + if (err) { /* match or error */
> > err = 0;
> > if (msg_type == AUDIT_USER_TTY) {
> > err = tty_audit_push_current();
> > diff --git a/kernel/auditfilter.c b/kernel/auditfilter.c
> > index b4c6e03..1a7dfa5 100644
> > --- a/kernel/auditfilter.c
> > +++ b/kernel/auditfilter.c
> > @@ -1272,8 +1272,8 @@ static int audit_filter_user_rules(struct audit_krule *rule, int type,
> > break;
> > }
> >
> > - if (!result)
> > - return 0;
> > + if (result <= 0)
> > + return result;
> > }
> > switch (rule->action) {
> > case AUDIT_NEVER: *state = AUDIT_DISABLED; break;
> > @@ -1286,19 +1286,37 @@ int audit_filter_user(int type)
> > {
> > enum audit_state state = AUDIT_DISABLED;
> > struct audit_entry *e;
> > - int ret = 1;
> > -
> > - rcu_read_lock();
> > - list_for_each_entry_rcu(e, &audit_filter_list[AUDIT_FILTER_USER], list) {
> > - if (audit_filter_user_rules(&e->rule, type, &state)) {
> > - if (state == AUDIT_DISABLED)
> > - ret = 0;
> > - break;
> > + int rc, count = 0, retry = 0, ret = 1; /* Audit by default */
> > +#define FILTER_RETRY_LIMIT 5
> > +
> > + do {
> > + rcu_read_lock();
> > + list_for_each_entry_rcu(e,
> > + &audit_filter_list[AUDIT_FILTER_USER],
> > + list) {
> > + retry = 0;
> > + rc = audit_filter_user_rules(&e->rule, type, &state);
> > + if (rc > 0) {
> > + if (state == AUDIT_DISABLED)
> > + ret = 0;
> > + break;
> > + } else if (rc < 0) {
> > + if (rc == -ESTALE && count < FILTER_RETRY_LIMIT) {
> > + rcu_read_unlock();
> > + count++;
> > + retry = 1;
> > + cond_resched();
> > + } else {
> > + ret = rc;
> > + }
> > + break;
> > + }
> > }
> > - }
> > - rcu_read_unlock();
> > + if (!retry)
> > + rcu_read_unlock();
> > + } while (retry);
> >
> > - return ret; /* Audit by default */
> > + return ret;
> > }
> >
> > int audit_filter_type(int type)
>
>
- RGB
--
Richard Guy Briggs <rbriggs@...hat.com>
Senior Software Engineer, Kernel Security, AMER ENG Base Operating Systems, Red Hat
Remote, Ottawa, Canada
Voice: +1.647.777.2635, Internal: (81) 32635, Alt: +1.613.693.0684x3545
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