From mboxrd@z Thu Jan 1 00:00:00 1970 From: Trond Myklebust Subject: [PATCH 24/24] NFS: Prevent the mount code from looping forever on broken exports Date: Fri, 16 Apr 2010 16:31:22 -0400 Message-ID: <1271449882-8580-25-git-send-email-Trond.Myklebust@netapp.com> References: <1271449882-8580-1-git-send-email-Trond.Myklebust@netapp.com> <1271449882-8580-2-git-send-email-Trond.Myklebust@netapp.com> <1271449882-8580-3-git-send-email-Trond.Myklebust@netapp.com> <1271449882-8580-4-git-send-email-Trond.Myklebust@netapp.com> <1271449882-8580-5-git-send-email-Trond.Myklebust@netapp.com> <1271449882-8580-6-git-send-email-Trond.Myklebust@netapp.com> <1271449882-8580-7-git-send-email-Trond.Myklebust@netapp.com> <1271449882-8580-8-git-send-email-Trond.Myklebust@netapp.com> <1271449882-8580-9-git-send-email-Trond.Myklebust@netapp.com> <1271449882-8580-10-git-send-email-Trond.Myklebust@netapp.com> <1271449882-8580-11-git-send-email-Trond.Myklebust@netapp.com> <1271449882-8580-12-git-send-email-Trond.Myklebust@netapp.com> <1271449882-8580-13-git-send-email-Trond.Myklebust@netapp.com> <1271449882-8580-14-git-send-email-Trond.Myklebust@netapp.com> <1271449882-8580-15-git-send-email-Trond.Myklebust@netapp.com> <1271449882-8580-16-git-send-email-Trond.Myklebust@netapp.com> <1271449882-8580-17-git-send-email-Trond.Myklebust@netapp.com> <1271449882-8580-18-git-send-email-Trond.Myklebust@netapp.com> <1271449882-8580-19-git-send-email-Trond.Myklebust@netapp.com> <1271449882-8580-20-git-send-email-Trond.Myklebust@netapp.com> <1271449882-8580-21-git-send-email-Trond.Myklebust@netapp.com> <1271449882-8580-22-git-send-email-Trond.Myklebust@netapp.com> <1271449882-8580-23-git-send-email-Trond.Myklebust@netapp.com> <1271449882-8580-24-git-send-email-Trond.Myklebust@netapp.com> To: linux-nfs@vger.kernel.org Return-path: Received: from mx2.netapp.com ([216.240.18.37]:16405 "EHLO mx2.netapp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932488Ab0DPUbn (ORCPT ); Fri, 16 Apr 2010 16:31:43 -0400 Received: from localhost.localdomain (marilynd-lxp.hq.netapp.com [10.58.50.136] (may be forged)) by smtp1.corp.netapp.com (8.13.1/8.13.1/NTAP-1.6) with ESMTP id o3GKVMlJ026251 for ; Fri, 16 Apr 2010 13:31:39 -0700 (PDT) In-Reply-To: <1271449882-8580-24-git-send-email-Trond.Myklebust@netapp.com> Sender: linux-nfs-owner@vger.kernel.org List-ID: Keep a global count of how many referrals that the current task has traversed on a path lookup. Return ELOOP if the count exceeds MAX_NESTED_LINKS. Signed-off-by: Trond Myklebust --- fs/nfs/super.c | 73 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 files changed, 73 insertions(+), 0 deletions(-) diff --git a/fs/nfs/super.c b/fs/nfs/super.c index cb196eb..33f355f 100644 --- a/fs/nfs/super.c +++ b/fs/nfs/super.c @@ -2672,6 +2672,72 @@ out_freepage: free_page((unsigned long)page); } +struct nfs_referral_count { + struct list_head list; + const struct task_struct *task; + unsigned int referral_count; +}; + +static LIST_HEAD(nfs_referral_count_list); +static DEFINE_SPINLOCK(nfs_referral_count_list_lock); + +static struct nfs_referral_count *nfs_find_referral_count(void) +{ + struct nfs_referral_count *p; + + list_for_each_entry(p, &nfs_referral_count_list, list) { + if (p->task == current) + return p; + } + return NULL; +} + +#define NFS_MAX_NESTED_REFERRALS 2 + +static int nfs_referral_loop_protect(void) +{ + struct nfs_referral_count *p, *new; + int ret = -ENOMEM; + + new = kmalloc(sizeof(*new), GFP_KERNEL); + if (!new) + goto out; + new->task = current; + new->referral_count = 1; + + ret = 0; + spin_lock(&nfs_referral_count_list_lock); + p = nfs_find_referral_count(); + if (p != NULL) { + if (p->referral_count >= NFS_MAX_NESTED_REFERRALS) + ret = -ELOOP; + else + p->referral_count++; + } else { + list_add(&new->list, &nfs_referral_count_list); + new = NULL; + } + spin_unlock(&nfs_referral_count_list_lock); + kfree(new); +out: + return ret; +} + +static void nfs_referral_loop_unprotect(void) +{ + struct nfs_referral_count *p; + + spin_lock(&nfs_referral_count_list_lock); + p = nfs_find_referral_count(); + p->referral_count--; + if (p->referral_count == 0) + list_del(&p->list); + else + p = NULL; + spin_unlock(&nfs_referral_count_list_lock); + kfree(p); +} + static int nfs_follow_remote_path(struct vfsmount *root_mnt, const char *export_path, struct vfsmount *mnt_target) { @@ -2689,9 +2755,14 @@ static int nfs_follow_remote_path(struct vfsmount *root_mnt, if (IS_ERR(ns_private)) goto out_mntput; + ret = nfs_referral_loop_protect(); + if (ret != 0) + goto out_put_mnt_ns; + ret = vfs_path_lookup(root_mnt->mnt_root, root_mnt, export_path, LOOKUP_FOLLOW, nd); + nfs_referral_loop_unprotect(); put_mnt_ns(ns_private); if (ret != 0) @@ -2709,6 +2780,8 @@ static int nfs_follow_remote_path(struct vfsmount *root_mnt, kfree(nd); down_write(&s->s_umount); return 0; +out_put_mnt_ns: + put_mnt_ns(ns_private); out_mntput: mntput(root_mnt); out_err: -- 1.6.6.1