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NFS: Detect loops in a readdir due to bad cookies

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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 <bjschuma@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
This commit is contained in:
Bryan Schumaker 2011-03-23 15:04:31 -04:00 • committed by Trond Myklebust
parent 480c2006eb
commit 8ef2ce3e16
2 changed files with 29 additions and 1 deletions
Download patch file Download diff file Expand all files Collapse all files

28
fs/nfs/dir.c
View file

@ -139,7 +139,9 @@ static struct nfs_open_dir_context *alloc_nfs_open_dir_context(struct rpc_cred *
struct nfs_open_dir_context *ctx; struct nfs_open_dir_context *ctx;
ctx = kmalloc(sizeof(*ctx), GFP_KERNEL); ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
if (ctx != NULL) { if (ctx != NULL) {
ctx->duped = 0;
ctx->dir_cookie = 0; ctx->dir_cookie = 0;
ctx->dup_cookie = 0;
ctx->cred = get_rpccred(cred); ctx->cred = get_rpccred(cred);
} else } else
ctx = ERR_PTR(-ENOMEM); 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; loff_t diff = desc->file->f_pos - desc->current_index;
unsigned int index; unsigned int index;
struct nfs_open_dir_context *ctx = desc->file->private_data;
if (diff < 0) if (diff < 0)
goto out_eof; 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; index = (unsigned int)diff;
*desc->dir_cookie = array->array[index].cookie; *desc->dir_cookie = array->array[index].cookie;
desc->cache_entry_index = index; desc->cache_entry_index = index;
ctx->duped = 0;
return 0; return 0;
out_eof: out_eof:
desc->eof = 1; 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 nfs_readdir_search_for_cookie(struct nfs_cache_array *array, nfs_readdir_descriptor_t *desc)
{ {
int i; int i;
loff_t new_pos;
int status = -EAGAIN; int status = -EAGAIN;
struct nfs_open_dir_context *ctx = desc->file->private_data;
for (i = 0; i < array->size; i++) { for (i = 0; i < array->size; i++) {
if (array->array[i].cookie == *desc->dir_cookie) { 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; desc->cache_entry_index = i;
return 0; return 0;
} }
@ -732,6 +743,20 @@ int nfs_do_filldir(nfs_readdir_descriptor_t *desc, void *dirent,
int i = 0; int i = 0;
int res = 0; int res = 0;
struct nfs_cache_array *array = NULL; 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. "
"Offending cookie: %llu\n",
file->f_dentry->d_parent->d_name.name,
file->f_dentry->d_name.name,
*desc->dir_cookie);
}
res = -ELOOP;
goto out;
}
array = nfs_readdir_get_array(desc->page); array = nfs_readdir_get_array(desc->page);
if (IS_ERR(array)) { if (IS_ERR(array)) {
@ -914,6 +939,7 @@ static loff_t nfs_llseek_dir(struct file *filp, loff_t offset, int origin)
if (offset != filp->f_pos) { if (offset != filp->f_pos) {
filp->f_pos = offset; filp->f_pos = offset;
dir_ctx->dir_cookie = 0; dir_ctx->dir_cookie = 0;
dir_ctx->duped = 0;
} }
out: out:
mutex_unlock(&inode->i_mutex); mutex_unlock(&inode->i_mutex);

2
include/linux/nfs_fs.h
View file

@ -100,6 +100,8 @@ struct nfs_open_context {
struct nfs_open_dir_context { struct nfs_open_dir_context {
struct rpc_cred *cred; struct rpc_cred *cred;
__u64 dir_cookie; __u64 dir_cookie;
__u64 dup_cookie;
int duped;
}; };
/* /*