udf: Return -ENOMEM when allocation fails in udf_get_filename()

Return -ENOMEM when allocation fails in udf_get_filename(). Update
udf_pc_to_char(), udf_readdir(), and udf_find_entry() to handle the
error appropriately. This allows us to pass appropriate error to
userspace instead of corrupting symlink contents by omitting some path
elements.

Signed-off-by: Fabian Frederick <fabf@skynet.be>
Signed-off-by: Jan Kara <jack@suse.cz>
diff --git a/fs/udf/symlink.c b/fs/udf/symlink.c
index 8dfbc40..862535b 100644
--- a/fs/udf/symlink.c
+++ b/fs/udf/symlink.c
@@ -82,6 +82,9 @@
 			comp_len = udf_get_filename(sb, pc->componentIdent,
 						    pc->lengthComponentIdent,
 						    p, tolen);
+			if (comp_len < 0)
+				return comp_len;
+
 			p += comp_len;
 			tolen -= comp_len;
 			if (tolen == 0)