ext4: in ext4_seek_{hole,data}, return -ENXIO for negative offsets

BugLink: http://bugs.launchpad.net/bugs/1724836

commit 1bd8d6cd upstream.

In the ext4 implementations of SEEK_HOLE and SEEK_DATA, make sure we
return -ENXIO for negative offsets instead of banging around inside
the extent code and returning -EFSCORRUPTED.
Reported-by: Mateusz S <muttdini@gmail.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

fs/ext4/file.c

@@ -558,7 +558,7 @@ static loff_t ext4_seek_data(struct file *file, loff_t offset, loff_t maxsize)
 	mutex_lock(&inode->i_mutex);
 
 	isize = i_size_read(inode);
-	if (offset >= isize) {
+	if (offset < 0 || offset >= isize) {
 		mutex_unlock(&inode->i_mutex);
 		return -ENXIO;
 	}
@@ -621,7 +621,7 @@ static loff_t ext4_seek_hole(struct file *file, loff_t offset, loff_t maxsize)
 	mutex_lock(&inode->i_mutex);
 
 	isize = i_size_read(inode);
-	if (offset >= isize) {
+	if (offset < 0 || offset >= isize) {
 		mutex_unlock(&inode->i_mutex);
 		return -ENXIO;
 	}