vfs: ensure page symlinks are NUL-terminated

On-disk data corruption could cause a page link to have its i_size set to PAGE_SIZE (or a multiple thereof) and its contents all non-NUL. NUL-terminate the link name to ensure this doesn't cause further problems for the kernel. Cc: Al Viro <[email protected]> Cc: Andrew Morton <[email protected]> Signed-off-by: Duane Griffin <[email protected]> Signed-off-by: Al Viro <[email protected]>
chewitt · Dec 31, 2008 · ebd09ab · ebd09ab
1 parent 0351468
commit ebd09ab
Showing 1 changed file with 5 additions and 2 deletions.
diff --git a/fs/namei.c b/fs/namei.c
@@ -2786,13 +2786,16 @@ int vfs_follow_link(struct nameidata *nd, const char *link)
 /* get the link contents into pagecache */
 static char *page_getlink(struct dentry * dentry, struct page **ppage)
 {
-	struct page * page;
+	char *kaddr;
+	struct page *page;
 	struct address_space *mapping = dentry->d_inode->i_mapping;
 	page = read_mapping_page(mapping, 0, NULL);
 	if (IS_ERR(page))
 		return (char*)page;
 	*ppage = page;
-	return kmap(page);
+	kaddr = kmap(page);
+	nd_terminate_link(kaddr, dentry->d_inode->i_size, PAGE_SIZE - 1);
+	return kaddr;
 }
 
 int page_readlink(struct dentry *dentry, char __user *buffer, int buflen)