[PATCH 1/4] NFS: Fix memory leaks and corruption in readdir

[Trond Myklebust <trondmy@xxxxxxxxx>]

nfs_readdir_xdr_to_array() must not exit without having initialised
the array, so that the page cache deletion routines can safely
call nfs_readdir_clear_array().
Furthermore, we should ensure that if we exit nfs_readdir_filler()
with an error, we free up any page contents to prevent a leak
if we try to fill the page again.

Fixes: 11de3b11e08c ("NFS: Fix a memory leak in nfs_readdir")
Cc: stable@xxxxxxxxxxxxxxx # v2.6.37+
Signed-off-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
---
 fs/nfs/dir.c | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index 76404f53cf21..ba0d55930e8a 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -163,6 +163,17 @@ typedef struct {
 	bool eof;
 } nfs_readdir_descriptor_t;
 
+static
+void nfs_readdir_init_array(struct page *page)
+{
+	struct nfs_cache_array *array;
+
+	array = kmap_atomic(page);
+	memset(array, 0, sizeof(struct nfs_cache_array));
+	array->eof_index = -1;
+	kunmap_atomic(array);
+}
+
 /*
  * we are freeing strings created by nfs_add_to_readdir_array()
  */
@@ -175,6 +186,7 @@ void nfs_readdir_clear_array(struct page *page)
 	array = kmap_atomic(page);
 	for (i = 0; i < array->size; i++)
 		kfree(array->array[i].string.name);
+	array->size = 0;
 	kunmap_atomic(array);
 }
 
@@ -613,6 +625,8 @@ int nfs_readdir_xdr_to_array(nfs_readdir_descriptor_t *desc, struct page *page,
 	int status = -ENOMEM;
 	unsigned int array_size = ARRAY_SIZE(pages);
 
+	nfs_readdir_init_array(page);
+
 	entry.prev_cookie = 0;
 	entry.cookie = desc->last_cookie;
 	entry.eof = 0;
@@ -629,8 +643,6 @@ int nfs_readdir_xdr_to_array(nfs_readdir_descriptor_t *desc, struct page *page,
 	}
 
 	array = kmap(page);
-	memset(array, 0, sizeof(struct nfs_cache_array));
-	array->eof_index = -1;
 
 	status = nfs_readdir_alloc_pages(pages, array_size);
 	if (status < 0)
@@ -685,6 +697,7 @@ int nfs_readdir_filler(void *data, struct page* page)
 	unlock_page(page);
 	return 0;
  error:
+	nfs_readdir_clear_array(page);
 	unlock_page(page);
 	return ret;
 }
-- 
2.24.1