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@xxxxxxxxxx>
---
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
--
To unsubscribe from this list: send the line "unsubscribe linux-nfs" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
