configfs: Zero terminate data in configfs attribute writes.

Attributes in configfs are text files.  As such, most handlers expect to be
able to call functions like simple_strtoul() without checking the bounds
of the buffer.  Change the call to zero terminate the buffer before calling
the client's ->store() method.  This does reduce the attribute size from
PAGE_SIZE to PAGE_SIZE-1.

Also, change get_zeroed_page() to alloc_page(), as we are handling the
termination.

Signed-off-by: Joel Becker <joel.becker@oracle.com>
Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>

1 files changed, 6 insertions, 3 deletions

diff --git a/fs/configfs/file.c b/fs/configfs/file.c
index 2a7cb086e80..d98be5e0132 100644
--- a/fs/configfs/file.c
+++ b/fs/configfs/file.c
@@ -162,14 +162,17 @@ fill_write_buffer(struct configfs_buffer * buffer, const char __user * buf, size
         int error;
 
         if (!buffer->page)
-                buffer->page = (char *)get_zeroed_page(GFP_KERNEL);
+                buffer->page = (char *)__get_free_pages(GFP_KERNEL, 0);
         if (!buffer->page)
                 return -ENOMEM;
 
-        if (count > PAGE_SIZE)
-                count = PAGE_SIZE;
+        if (count >= PAGE_SIZE)
+                count = PAGE_SIZE - 1;
         error = copy_from_user(buffer->page,buf,count);
         buffer->needs_read_fill = 1;
+        /* if buf is assumed to contain a string, terminate it by \0,
+         * so e.g. sscanf() can scan the string easily */
+        buffer->page[count] = 0;
         return error ? -EFAULT : count;
 }