linux-kernel - [PATCH 3.16 95/99] NFS: Fix memory leaks and corruption in readdir

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Message-ID: <lsq.1589984009.495233844@decadent.org.uk>
Date:   Wed, 20 May 2020 15:15:03 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "Benjamin Coddington" <bcodding@...hat.com>,
        "Trond Myklebust" <trondmy@...il.com>,
        "Trond Myklebust" <trond.myklebust@...merspace.com>,
        "Anna Schumaker" <Anna.Schumaker@...app.com>
Subject: [PATCH 3.16 95/99] NFS: Fix memory leaks and corruption in readdir

3.16.84-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Trond Myklebust <trondmy@...il.com>

commit 4b310319c6a8ce708f1033d57145e2aa027a883c upstream.

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")
Signed-off-by: Trond Myklebust <trond.myklebust@...merspace.com>
Reviewed-by: Benjamin Coddington <bcodding@...hat.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@...app.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 fs/nfs/dir.c | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -169,6 +169,17 @@ typedef struct {
 	unsigned int	eof:1;
 } 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()
  */
@@ -181,6 +192,7 @@ void nfs_readdir_clear_array(struct page
 	array = kmap_atomic(page);
 	for (i = 0; i < array->size; i++)
 		kfree(array->array[i].string.name);
+	array->size = 0;
 	kunmap_atomic(array);
 }
 
@@ -580,6 +592,8 @@ int nfs_readdir_xdr_to_array(nfs_readdir
 	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;
@@ -596,8 +610,6 @@ int nfs_readdir_xdr_to_array(nfs_readdir
 	}
 
 	array = kmap(page);
-	memset(array, 0, sizeof(struct nfs_cache_array));
-	array->eof_index = -1;
 
 	status = nfs_readdir_large_page(pages, array_size);
 	if (status < 0)
@@ -651,6 +663,7 @@ int nfs_readdir_filler(nfs_readdir_descr
 	unlock_page(page);
 	return 0;
  error:
+	nfs_readdir_clear_array(page);
 	unlock_page(page);
 	return ret;
 }