UBIFS: Fix potential integer overflow in allocation

There is potential for the size and len fields in ubifs_data_node to be
too large causing either a negative value for the length fields or an
integer overflow leading to an incorrect memory allocation. Likewise,
when the len field is small, an integer underflow may occur.

Signed-off-by: Silvio Cesare <silvio.cesare@gmail.com>
Fixes: 1e51764a3c2ac ("UBIFS: add new flash file system")
Cc: stable@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>

fs/ubifs/journal.c

@@ -1282,10 +1282,11 @@ static int truncate_data_node(const struct ubifs_info *c, const struct inode *in
 			      int *new_len)
 {
 	void *buf;
-	int err, dlen, compr_type, out_len, old_dlen;
+	int err, compr_type;
+	u32 dlen, out_len, old_dlen;
 
 	out_len = le32_to_cpu(dn->size);
-	buf = kmalloc(out_len * WORST_COMPR_FACTOR, GFP_NOFS);
+	buf = kmalloc_array(out_len, WORST_COMPR_FACTOR, GFP_NOFS);
 	if (!buf)
 		return -ENOMEM;