Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759171Ab1D0NM3 (ORCPT ); Wed, 27 Apr 2011 09:12:29 -0400 Received: from cantor.suse.de ([195.135.220.2]:39855 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759118Ab1D0NM2 (ORCPT ); Wed, 27 Apr 2011 09:12:28 -0400 Date: Wed, 27 Apr 2011 15:12:23 +0200 (CEST) From: Jiri Kosina X-X-Sender: jikos@twin.jikos.cz To: Eric Paris Cc: Tony Jones , David Howells , linux-kernel@vger.kernel.org, linux-audit@redhat.com, Al Viro Subject: Re: PATCH [1/1]: audit: acquire creds selectively to reduce atomic op overhead In-Reply-To: <1300715854.2744.0.camel@unknown001a4b0c2895> Message-ID: References: <1300211077.3748.2.camel@localhost.localdomain> <20110310202516.GA16122@suse.de> <20110307210656.GA1750@suse.de> <18893.1299607373@redhat.com> <29980.1299861232@redhat.com> <20110315173810.GA12775@suse.de> <21526.1300219877@redhat.com> <20110317181159.GA31948@suse.de> <1300715854.2744.0.camel@unknown001a4b0c2895> User-Agent: Alpine 2.00 (LRH 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4600 Lines: 120 On Mon, 21 Mar 2011, Eric Paris wrote: > > Commit c69e8d9c01db added calls to get_task_cred and put_cred in > > audit_filter_rules. Profiling with a large number of audit rules active on the > > exit chain shows that we are spending upto 48% in this routine for syscall > > intensive tests, most of which is in the atomic ops. > > > > 1. The code should be accessing tsk->cred rather than tsk->real_cred. > > 2. Since tsk is current (or tsk is being created by copy_process) access to > > tsk->cred without rcu read lock is possible. At the request of the audit > > maintainer, a new flag has been added to audit_filter_rules in order to make > > this explicit and guide future code. > > > > Signed-off-by: Tony Jones > > Acked-by: Eric Paris I don't see the patch in linux-next as of today. As it has been acked by subsystem maintainer, I have picked it up into my tree ("retransmission mode"). If anyone has any objections, please let me know. Thanks. > > > --- > > kernel/auditsc.c | 27 +++++++++++++++++---------- > > 1 files changed, 17 insertions(+), 10 deletions(-) > > > > diff --git a/kernel/auditsc.c b/kernel/auditsc.c > > index f49a031..281dcf1 100644 > > --- a/kernel/auditsc.c > > +++ b/kernel/auditsc.c > > @@ -443,17 +443,25 @@ static int match_tree_refs(struct audit_context *ctx, struct audit_tree *tree) > > > > /* Determine if any context name data matches a rule's watch data */ > > /* Compare a task_struct with an audit_rule. Return 1 on match, 0 > > - * otherwise. */ > > + * otherwise. > > + * > > + * If task_creation is true, this is an explicit indication that we are > > + * filtering a task rule at task creation time. This and tsk == current are > > + * the only situations where tsk->cred may be accessed without an rcu read lock. > > + */ > > static int audit_filter_rules(struct task_struct *tsk, > > struct audit_krule *rule, > > struct audit_context *ctx, > > struct audit_names *name, > > - enum audit_state *state) > > + enum audit_state *state, > > + bool task_creation) > > { > > - const struct cred *cred = get_task_cred(tsk); > > + const struct cred *cred; > > int i, j, need_sid = 1; > > u32 sid; > > > > + cred = rcu_dereference_check(tsk->cred, tsk == current || task_creation); > > + > > for (i = 0; i < rule->field_count; i++) { > > struct audit_field *f = &rule->fields[i]; > > int result = 0; > > @@ -637,10 +645,8 @@ static int audit_filter_rules(struct task_struct *tsk, > > break; > > } > > > > - if (!result) { > > - put_cred(cred); > > + if (!result) > > return 0; > > - } > > } > > > > if (ctx) { > > @@ -656,7 +662,6 @@ static int audit_filter_rules(struct task_struct *tsk, > > case AUDIT_NEVER: *state = AUDIT_DISABLED; break; > > case AUDIT_ALWAYS: *state = AUDIT_RECORD_CONTEXT; break; > > } > > - put_cred(cred); > > return 1; > > } > > > > @@ -671,7 +676,8 @@ static enum audit_state audit_filter_task(struct task_struct *tsk, char **key) > > > > rcu_read_lock(); > > list_for_each_entry_rcu(e, &audit_filter_list[AUDIT_FILTER_TASK], list) { > > - if (audit_filter_rules(tsk, &e->rule, NULL, NULL, &state)) { > > + if (audit_filter_rules(tsk, &e->rule, NULL, NULL, > > + &state, true)) { > > if (state == AUDIT_RECORD_CONTEXT) > > *key = kstrdup(e->rule.filterkey, GFP_ATOMIC); > > rcu_read_unlock(); > > @@ -705,7 +711,7 @@ static enum audit_state audit_filter_syscall(struct task_struct *tsk, > > list_for_each_entry_rcu(e, list, list) { > > if ((e->rule.mask[word] & bit) == bit && > > audit_filter_rules(tsk, &e->rule, ctx, NULL, > > - &state)) { > > + &state, false)) { > > rcu_read_unlock(); > > ctx->current_state = state; > > return state; > > @@ -743,7 +749,8 @@ void audit_filter_inodes(struct task_struct *tsk, struct audit_context *ctx) > > > > list_for_each_entry_rcu(e, list, list) { > > if ((e->rule.mask[word] & bit) == bit && > > - audit_filter_rules(tsk, &e->rule, ctx, n, &state)) { > > + audit_filter_rules(tsk, &e->rule, ctx, n, > > + &state, false)) { > > rcu_read_unlock(); > > ctx->current_state = state; > > return; -- Jiri Kosina SUSE Labs, Novell Inc. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/