ext3: ext3_bread usage audit

This is the ext3 version of the same patch applied to Ext4, where such goal is
to audit the usage of ext3_bread() due a possible misinterpretion of its return
value.

Focused on directory blocks, a NULL value returned from ext3_bread() means a
hole, which cannot exist into a directory inode. It can pass undetected after a
fix in an uninitialized error variable.

The (now) initialized variable into ext3_getblk() may lead to a zero'ed return
value of ext3_bread() to its callers, which can make the caller do not detect
the hole in the directory inode.

This patch creates a new wrapper function ext3_dir_bread() which checks for
holes properly, reports error, and returns EIO in that case.

Signed-off-by: Carlos Maiolino <cmaiolino@redhat.com>
Signed-off-by: Jan Kara <jack@suse.cz>

1 files changed, 19 insertions, 0 deletions

diff --git a/fs/ext3/namei.h b/fs/ext3/namei.h
index f2ce2b0..46304d8 100644
--- a/fs/ext3/namei.h
+++ b/fs/ext3/namei.h
@@ -6,3 +6,22 @@
 */
 
 extern struct dentry *ext3_get_parent(struct dentry *child);
+
+static inline struct buffer_head *ext3_dir_bread(handle_t *handle,
+						 struct inode *inode,
+						 int block, int create,
+						 int *err)
+{
+	struct buffer_head *bh;
+
+	bh = ext3_bread(handle, inode, block, create, err);
+
+	if (!bh && !(*err)) {
+		*err = -EIO;
+		ext3_error(inode->i_sb, __func__,
+			   "Directory hole detected on inode %lu\n",
+			   inode->i_ino);
+		return NULL;
+	}
+	return bh;
+}