From patchwork Thu Feb 20 20:49:09 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Eric W. Biederman" X-Patchwork-Id: 11395013 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 9666992A for ; Thu, 20 Feb 2020 20:51:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8044C208CD for ; Thu, 20 Feb 2020 20:51:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728865AbgBTUvY (ORCPT ); Thu, 20 Feb 2020 15:51:24 -0500 Received: from out02.mta.xmission.com ([166.70.13.232]:48810 "EHLO out02.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728618AbgBTUvX (ORCPT ); Thu, 20 Feb 2020 15:51:23 -0500 Received: from in01.mta.xmission.com ([166.70.13.51]) by out02.mta.xmission.com with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1j4sn4-0001ko-94; Thu, 20 Feb 2020 13:51:22 -0700 Received: from ip68-227-160-95.om.om.cox.net ([68.227.160.95] helo=x220.xmission.com) by in01.mta.xmission.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.87) (envelope-from ) id 1j4smw-0005SC-BW; Thu, 20 Feb 2020 13:51:21 -0700 From: ebiederm@xmission.com (Eric W. Biederman) To: Linus Torvalds Cc: Al Viro , LKML , Kernel Hardening , Linux API , Linux FS Devel , Linux Security Module , Akinobu Mita , Alexey Dobriyan , Andrew Morton , Andy Lutomirski , Daniel Micay , Djalal Harouni , "Dmitry V . Levin" , Greg Kroah-Hartman , Ingo Molnar , "J . Bruce Fields" , Jeff Layton , Jonathan Corbet , Kees Cook , Oleg Nesterov , Solar Designer References: <20200210150519.538333-8-gladkov.alexey@gmail.com> <87v9odlxbr.fsf@x220.int.ebiederm.org> <20200212144921.sykucj4mekcziicz@comp-core-i7-2640m-0182e6> <87tv3vkg1a.fsf@x220.int.ebiederm.org> <87v9obipk9.fsf@x220.int.ebiederm.org> <20200212200335.GO23230@ZenIV.linux.org.uk> <20200212203833.GQ23230@ZenIV.linux.org.uk> <20200212204124.GR23230@ZenIV.linux.org.uk> <87lfp7h422.fsf@x220.int.ebiederm.org> <87pnejf6fz.fsf@x220.int.ebiederm.org> <871rqpaswu.fsf_-_@x220.int.ebiederm.org> Date: Thu, 20 Feb 2020 14:49:09 -0600 In-Reply-To: <871rqpaswu.fsf_-_@x220.int.ebiederm.org> (Eric W. Biederman's message of "Thu, 20 Feb 2020 14:46:25 -0600") Message-ID: <87h7zl9e7u.fsf_-_@x220.int.ebiederm.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) MIME-Version: 1.0 X-XM-SPF: eid=1j4smw-0005SC-BW;;;mid=<87h7zl9e7u.fsf_-_@x220.int.ebiederm.org>;;;hst=in01.mta.xmission.com;;;ip=68.227.160.95;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX18yxsTIN6rEo+POZRFDqs4bpwfG8Bf38/Y= X-SA-Exim-Connect-IP: 68.227.160.95 X-SA-Exim-Mail-From: ebiederm@xmission.com X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on sa01.xmission.com X-Spam-Level: **** X-Spam-Status: No, score=4.0 required=8.0 tests=ALL_TRUSTED,BAYES_50, DCC_CHECK_NEGATIVE,NO_DNS_FOR_FROM,TR_Symld_Words,T_TooManySym_01, T_TooManySym_02,T_TooManySym_03,T_TooManySym_04,XMGappySubj_01, XMNoVowels,XMSubLong autolearn=disabled version=3.4.2 X-Spam-Virus: No X-Spam-Report: * -1.0 ALL_TRUSTED Passed through trusted hosts only via SMTP * 0.8 BAYES_50 BODY: Bayes spam probability is 40 to 60% * [score: 0.5000] * 0.7 XMSubLong Long Subject * 0.5 XMGappySubj_01 Very gappy subject * 1.5 TR_Symld_Words too many words that have symbols inside * 1.5 XMNoVowels Alpha-numberic number with no vowels * -0.0 DCC_CHECK_NEGATIVE Not listed in DCC * [sa01 1397; Body=1 Fuz1=1 Fuz2=1] * 0.0 NO_DNS_FOR_FROM DNS: Envelope sender has no MX or A DNS records * 0.0 T_TooManySym_02 5+ unique symbols in subject * 0.0 T_TooManySym_01 4+ unique symbols in subject * 0.0 T_TooManySym_03 6+ unique symbols in subject * 0.0 T_TooManySym_04 7+ unique symbols in subject X-Spam-DCC: XMission; sa01 1397; Body=1 Fuz1=1 Fuz2=1 X-Spam-Combo: ****;Linus Torvalds X-Spam-Relay-Country: X-Spam-Timing: total 7271 ms - load_scoreonly_sql: 0.03 (0.0%), signal_user_changed: 2.9 (0.0%), b_tie_ro: 2.1 (0.0%), parse: 1.16 (0.0%), extract_message_metadata: 12 (0.2%), get_uri_detail_list: 1.32 (0.0%), tests_pri_-1000: 3.4 (0.0%), tests_pri_-950: 0.98 (0.0%), tests_pri_-900: 0.84 (0.0%), tests_pri_-90: 21 (0.3%), check_bayes: 20 (0.3%), b_tokenize: 6 (0.1%), b_tok_get_all: 7 (0.1%), b_comp_prob: 1.55 (0.0%), b_tok_touch_all: 3.9 (0.1%), b_finish: 0.62 (0.0%), tests_pri_0: 6184 (85.0%), check_dkim_signature: 0.38 (0.0%), check_dkim_adsp: 6008 (82.6%), poll_dns_idle: 7038 (96.8%), tests_pri_10: 1.66 (0.0%), tests_pri_500: 1041 (14.3%), rewrite_mail: 0.00 (0.0%) Subject: [PATCH 3/7] proc: Mov rcu_read_(lock|unlock) in proc_prune_siblings_dcache X-Spam-Flag: No X-SA-Exim-Version: 4.2.1 (built Thu, 05 May 2016 13:38:54 -0600) X-SA-Exim-Scanned: Yes (on in01.mta.xmission.com) Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: Don't make it look like rcu_read_lock is held over the entire loop instead just take the rcu_read_lock over the part of the loop that matters. This makes the intent of the code a little clearer. Signed-off-by: "Eric W. Biederman" --- fs/proc/inode.c | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-) diff --git a/fs/proc/inode.c b/fs/proc/inode.c index 74ce4a8d05eb..38a7baa41aba 100644 --- a/fs/proc/inode.c +++ b/fs/proc/inode.c @@ -110,11 +110,13 @@ void proc_prune_siblings_dcache(struct hlist_head *inodes, spinlock_t *lock) struct hlist_node *node; struct super_block *sb; - rcu_read_lock(); for (;;) { + rcu_read_lock(); node = hlist_first_rcu(inodes); - if (!node) + if (!node) { + rcu_read_unlock(); break; + } ei = hlist_entry(node, struct proc_inode, sibling_inodes); spin_lock(lock); hlist_del_init_rcu(&ei->sibling_inodes); @@ -122,23 +124,21 @@ void proc_prune_siblings_dcache(struct hlist_head *inodes, spinlock_t *lock) inode = &ei->vfs_inode; sb = inode->i_sb; - if (!atomic_inc_not_zero(&sb->s_active)) + if (!atomic_inc_not_zero(&sb->s_active)) { + rcu_read_unlock(); continue; + } inode = igrab(inode); rcu_read_unlock(); if (unlikely(!inode)) { deactivate_super(sb); - rcu_read_lock(); continue; } d_prune_aliases(inode); iput(inode); deactivate_super(sb); - - rcu_read_lock(); } - rcu_read_unlock(); } static int proc_show_options(struct seq_file *seq, struct dentry *root)