From: Bryan Schumaker Subject: [PATCH v2 3/3] NFS: Detect loops in a readdir due to bad cookies Date: Wed, 23 Mar 2011 14:48:31 -0400 Message-ID: <4D8A407F.40105@netapp.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Cc: "linux-nfs@vger.kernel.org" To: "Myklebust, Trond" Return-path: Received: from mx2.netapp.com ([216.240.18.37]:5931 "EHLO mx2.netapp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932587Ab1CWSsc (ORCPT ); Wed, 23 Mar 2011 14:48:32 -0400 Sender: linux-nfs-owner@vger.kernel.org List-ID: Some filesystems (such as ext4) can return the same cookie value for multiple files. If we try to start a readdir with one of these cookies, the server will return the first file found with a cookie of the same value. This can cause the client to enter an infinite loop. Signed-off-by: Bryan Schumaker --- fs/nfs/dir.c | 26 +++++++++++++++++++++++++- include/linux/nfs_fs.h | 2 ++ 2 files changed, 27 insertions(+), 1 deletions(-) diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c index 112494a..64fa9fc 100644 --- a/fs/nfs/dir.c +++ b/fs/nfs/dir.c @@ -139,7 +139,9 @@ static struct nfs_open_dir_context *alloc_nfs_open_dir_context(struct rpc_cred * struct nfs_open_dir_context *ctx; ctx = kmalloc(sizeof(*ctx), GFP_KERNEL); if (ctx != NULL) { + ctx->duped = 0; ctx->dir_cookie = 0; + ctx->dup_cookie = 0; ctx->cred = get_rpccred(cred); } else ctx = ERR_PTR(-ENOMEM); @@ -321,6 +323,7 @@ int nfs_readdir_search_for_pos(struct nfs_cache_array *array, nfs_readdir_descri { loff_t diff = desc->file->f_pos - desc->current_index; unsigned int index; + struct nfs_open_dir_context *ctx = desc->file->private_data; if (diff < 0) goto out_eof; @@ -333,6 +336,7 @@ int nfs_readdir_search_for_pos(struct nfs_cache_array *array, nfs_readdir_descri index = (unsigned int)diff; *desc->dir_cookie = array->array[index].cookie; desc->cache_entry_index = index; + ctx->duped = 0; return 0; out_eof: desc->eof = 1; @@ -343,11 +347,18 @@ static int nfs_readdir_search_for_cookie(struct nfs_cache_array *array, nfs_readdir_descriptor_t *desc) { int i; + loff_t new_pos; int status = -EAGAIN; + struct nfs_open_dir_context *ctx = desc->file->private_data; for (i = 0; i < array->size; i++) { if (array->array[i].cookie == *desc->dir_cookie) { - desc->file->f_pos = desc->current_index + i; + new_pos = desc->current_index + i; + if (new_pos < desc->file->f_pos) { + ctx->dup_cookie = *desc->dir_cookie; + ctx->duped = 1; + } + desc->file->f_pos = new_pos; desc->cache_entry_index = i; return 0; } @@ -732,6 +743,18 @@ int nfs_do_filldir(nfs_readdir_descriptor_t *desc, void *dirent, int i = 0; int res = 0; struct nfs_cache_array *array = NULL; + struct nfs_open_dir_context *ctx = file->private_data; + + if (ctx->duped != 0 && ctx->dup_cookie == *desc->dir_cookie) { + if (printk_ratelimit()) { + pr_notice("NFS: directory %s/%s contains a readdir loop. " + "Please contact your server vendor.", + file->f_dentry->d_parent->d_name.name, + file->f_dentry->d_name.name); + } + res = -ELOOP; + goto out; + } array = nfs_readdir_get_array(desc->page); if (IS_ERR(array)) { @@ -900,6 +923,7 @@ static loff_t nfs_llseek_dir(struct file *filp, loff_t offset, int origin) dentry->d_name.name, offset, origin); + dir_ctx->duped = 0; mutex_lock(&inode->i_mutex); switch (origin) { case 1: diff --git a/include/linux/nfs_fs.h b/include/linux/nfs_fs.h index 4b87c00..69d6fc9 100644 --- a/include/linux/nfs_fs.h +++ b/include/linux/nfs_fs.h @@ -98,6 +98,8 @@ struct nfs_open_context { struct nfs_open_dir_context { struct rpc_cred *cred; __u64 dir_cookie; + __u64 dup_cookie; + int duped; }; /* -- 1.7.4.1