From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752031AbaBRV2v (ORCPT ); Tue, 18 Feb 2014 16:28:51 -0500 Received: from out02.mta.xmission.com ([166.70.13.232]:43767 "EHLO out02.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751005AbaBRV2t (ORCPT ); Tue, 18 Feb 2014 16:28:49 -0500 From: ebiederm@xmission.com (Eric W. Biederman) To: Miklos Szeredi Cc: Al Viro , "Serge E. Hallyn" , Linux-Fsdevel , Kernel Mailing List , Andy Lutomirski , Rob Landley , Linus Torvalds , Christoph Hellwig , Karel Zak , "J. Bruce Fields" References: <87a9kkax0j.fsf@xmission.com> <8761v7h2pt.fsf@tw-ebiederman.twitter.com> <87li281wx6.fsf_-_@xmission.com> <87ob28kqks.fsf_-_@xmission.com> <8761ogkqhl.fsf_-_@xmission.com> <20140218171252.GC4026@tucsk.piliscsaba.szeredi.hu> Date: Tue, 18 Feb 2014 13:28:36 -0800 In-Reply-To: <20140218171252.GC4026@tucsk.piliscsaba.szeredi.hu> (Miklos Szeredi's message of "Tue, 18 Feb 2014 18:12:52 +0100") Message-ID: <87ha7wrtyz.fsf@xmission.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-XM-AID: U2FsdGVkX18XcxEOcqnaXa6CyCUErwf7wEDKIecS17I= X-SA-Exim-Connect-IP: 98.207.154.105 X-SA-Exim-Mail-From: ebiederm@xmission.com X-Spam-Report: * -1.0 ALL_TRUSTED Passed through trusted hosts only via SMTP * 2.9 KHOP_BIG_TO_CC Sent to 10+ recipients instaed of Bcc or a list * 1.5 XMNoVowels Alpha-numberic number with no vowels * 0.7 XMSubLong Long Subject * 0.0 T_TM2_M_HEADER_IN_MSG BODY: T_TM2_M_HEADER_IN_MSG * -3.0 BAYES_00 BODY: Bayes spam probability is 0 to 1% * [score: 0.0024] * -0.0 DCC_CHECK_NEGATIVE Not listed in DCC * [sa03 1397; Body=1 Fuz1=1 Fuz2=1] * 0.0 T_TooManySym_01 4+ unique symbols in subject X-Spam-DCC: XMission; sa03 1397; Body=1 Fuz1=1 Fuz2=1 X-Spam-Combo: *;Miklos Szeredi X-Spam-Relay-Country: Subject: Re: [PATCH 03/11] vfs: Don't allow overwriting mounts in the current mount namespace X-Spam-Flag: No X-SA-Exim-Version: 4.2.1 (built Wed, 14 Nov 2012 14:26:46 -0700) X-SA-Exim-Scanned: Yes (on in02.mta.xmission.com) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org >> diff --git a/fs/namespace.c b/fs/namespace.c >> index 22e536705c45..6dc23614d44d 100644 >> --- a/fs/namespace.c >> +++ b/fs/namespace.c >> @@ -631,6 +631,41 @@ struct vfsmount *lookup_mnt(struct path *path) >> return m; >> } >> >> +/* >> + * __is_local_mountpoint - Test to see if dentry is a mountpoint in the >> + * current mount namespace. >> + * >> + * The common case is dentries are not mountpoints at all and that >> + * test is handled inline. For the slow case when we are actually >> + * dealing with a mountpoint of some kind, walk through all of the >> + * mounts in the current mount namespace and test to see if the dentry >> + * is a mountpoint. >> + * >> + * The mount_hashtable is not usable in the context because we >> + * need to identify all mounts that may be in the current mount >> + * namespace not just a mount that happens to have some specified >> + * parent mount. >> + */ >> +int __is_local_mountpoint(struct dentry *dentry) > > Minor nit: return value of any is_* function is either true or false, so why not > declare it bool? Because I am working on the core of the kernel and C compilers do weird things with bool variables (storing them in bytes...). I expected a type that the C compiler does not do weird things with would be more readily received on a path whose performance people are interested in. >> +{ >> + struct mnt_namespace *ns = current->nsproxy->mnt_ns; >> + struct mount *mnt; >> + int is_covered = 0; > > And the same for this var. > >> + >> + if (!d_mountpoint(dentry)) >> + goto out; >> + >> + down_read(&namespace_sem); >> + list_for_each_entry(mnt, &ns->list, mnt_list) { >> + is_covered = (mnt->mnt_mountpoint == dentry); >> + if (is_covered) >> + break; >> + } >> + up_read(&namespace_sem); >> +out: >> + return is_covered; >> +} >> + >> static struct mountpoint *new_mountpoint(struct dentry *dentry) >> { >> struct list_head *chain = mountpoint_hashtable + hash(NULL, dentry); >> -- >> 1.7.5.4 Eric