From patchwork Mon Feb 24 16:27:49 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: 11400959 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 99C601395 for ; Mon, 24 Feb 2020 16:30:08 +0000 (UTC) Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.kernel.org (Postfix) with SMTP id 0AE5A2080D for ; Mon, 24 Feb 2020 16:30:07 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0AE5A2080D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=xmission.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kernel-hardening-return-17894-patchwork-kernel-hardening=patchwork.kernel.org@lists.openwall.com Received: (qmail 22265 invoked by uid 550); 24 Feb 2020 16:30:06 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Delivered-To: mailing list kernel-hardening@lists.openwall.com Received: (qmail 22226 invoked from network); 24 Feb 2020 16:30:05 -0000 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 , Alexey Gladkov 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> <871rqk2brn.fsf_-_@x220.int.ebiederm.org> Date: Mon, 24 Feb 2020 10:27:49 -0600 In-Reply-To: <871rqk2brn.fsf_-_@x220.int.ebiederm.org> (Eric W. Biederman's message of "Mon, 24 Feb 2020 10:25:16 -0600") Message-ID: <87k14c0x2y.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=1j6GcC-0007x0-LM;;;mid=<87k14c0x2y.fsf_-_@x220.int.ebiederm.org>;;;hst=in01.mta.xmission.com;;;ip=68.227.160.95;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX1/PBz/fWPf6jpbA0LkgeAc4T35MgRRLVLo= 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 sa06.xmission.com X-Spam-Level: * X-Spam-Status: No, score=1.0 required=8.0 tests=ALL_TRUSTED,BAYES_50, DCC_CHECK_NEGATIVE,T_TooManySym_01,XMGappySubj_01,XMSubLong autolearn=disabled version=3.4.2 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] * 0.5 XMGappySubj_01 Very gappy subject * 0.7 XMSubLong Long Subject * -0.0 DCC_CHECK_NEGATIVE Not listed in DCC * [sa06 1397; Body=1 Fuz1=1 Fuz2=1] * 0.0 T_TooManySym_01 4+ unique symbols in subject X-Spam-DCC: XMission; sa06 1397; Body=1 Fuz1=1 Fuz2=1 X-Spam-Combo: *;Linus Torvalds X-Spam-Relay-Country: X-Spam-Timing: total 473 ms - load_scoreonly_sql: 0.12 (0.0%), signal_user_changed: 3.2 (0.7%), b_tie_ro: 2.0 (0.4%), parse: 2.1 (0.4%), extract_message_metadata: 14 (3.0%), get_uri_detail_list: 1.62 (0.3%), tests_pri_-1000: 16 (3.3%), tests_pri_-950: 1.35 (0.3%), tests_pri_-900: 1.15 (0.2%), tests_pri_-90: 28 (6.0%), check_bayes: 27 (5.6%), b_tokenize: 9 (1.9%), b_tok_get_all: 7 (1.5%), b_comp_prob: 2.5 (0.5%), b_tok_touch_all: 6 (1.2%), b_finish: 0.95 (0.2%), tests_pri_0: 390 (82.4%), check_dkim_signature: 0.81 (0.2%), check_dkim_adsp: 2.5 (0.5%), poll_dns_idle: 0.57 (0.1%), tests_pri_10: 2.1 (0.4%), tests_pri_500: 11 (2.3%), rewrite_mail: 0.00 (0.0%) Subject: [PATCH v2 3/6] proc: In proc_prune_siblings_dcache cache an aquired super block 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) Because there are likely to be several sysctls in a row on the same superblock cache the super_block after the count has been raised and don't deactivate it until we are processing another super_block. Signed-off-by: "Eric W. Biederman" --- fs/proc/inode.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) diff --git a/fs/proc/inode.c b/fs/proc/inode.c index 74ce4a8d05eb..fa2dc732cd77 100644 --- a/fs/proc/inode.c +++ b/fs/proc/inode.c @@ -108,10 +108,11 @@ void proc_prune_siblings_dcache(struct hlist_head *inodes, spinlock_t *lock) struct inode *inode; struct proc_inode *ei; struct hlist_node *node; - struct super_block *sb; + struct super_block *old_sb = NULL; rcu_read_lock(); for (;;) { + struct super_block *sb; node = hlist_first_rcu(inodes); if (!node) break; @@ -122,23 +123,28 @@ 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 ((sb != old_sb) && !atomic_inc_not_zero(&sb->s_active)) continue; inode = igrab(inode); rcu_read_unlock(); + if (sb != old_sb) { + if (old_sb) + deactivate_super(old_sb); + old_sb = sb; + } 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(); + if (old_sb) + deactivate_super(old_sb); } static int proc_show_options(struct seq_file *seq, struct dentry *root)