mei: fix transfer over dma with extended header

The size in header field for packet transferred over DMA
includes size of the extended header.
Include extended header in size check.
Add size and sanity checks on extended header.

Cc: <stable@vger.kernel.org> # v5.10+
Signed-off-by: Alexander Usyskin <alexander.usyskin@intel.com>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Link: https://lore.kernel.org/r/20210129120752.850325-1-tomas.winkler@intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/misc/mei/interrupt.c

@@ -295,12 +295,17 @@ static inline bool hdr_is_fixed(struct mei_msg_hdr *mei_hdr)
 static inline int hdr_is_valid(u32 msg_hdr)
 {
 	struct mei_msg_hdr *mei_hdr;
+	u32 expected_len = 0;
 
 	mei_hdr = (struct mei_msg_hdr *)&msg_hdr;
 	if (!msg_hdr || mei_hdr->reserved)
 		return -EBADMSG;
 
-	if (mei_hdr->dma_ring && mei_hdr->length != MEI_SLOT_SIZE)
+	if (mei_hdr->dma_ring)
+		expected_len += MEI_SLOT_SIZE;
+	if (mei_hdr->extended)
+		expected_len += MEI_SLOT_SIZE;
+	if (mei_hdr->length < expected_len)
 		return -EBADMSG;
 
 	return 0;
@@ -324,6 +329,8 @@ int mei_irq_read_handler(struct mei_device *dev,
 	struct mei_cl *cl;
 	int ret;
 	u32 ext_meta_hdr_u32;
+	u32 hdr_size_left;
+	u32 hdr_size_ext;
 	int i;
 	int ext_hdr_end;
 
@@ -353,6 +360,7 @@ int mei_irq_read_handler(struct mei_device *dev,
 	}
 
 	ext_hdr_end = 1;
+	hdr_size_left = mei_hdr->length;
 
 	if (mei_hdr->extended) {
 		if (!dev->rd_msg_hdr[1]) {
@@ -363,8 +371,21 @@ int mei_irq_read_handler(struct mei_device *dev,
 			dev_dbg(dev->dev, "extended header is %08x\n",
 				ext_meta_hdr_u32);
 		}
-		meta_hdr = ((struct mei_ext_meta_hdr *)
-				dev->rd_msg_hdr + 1);
+		meta_hdr = ((struct mei_ext_meta_hdr *)dev->rd_msg_hdr + 1);
+		if (check_add_overflow((u32)sizeof(*meta_hdr),
+				       mei_slots2data(meta_hdr->size),
+				       &hdr_size_ext)) {
+			dev_err(dev->dev, "extended message size too big %d\n",
+				meta_hdr->size);
+			return -EBADMSG;
+		}
+		if (hdr_size_left < hdr_size_ext) {
+			dev_err(dev->dev, "corrupted message header len %d\n",
+				mei_hdr->length);
+			return -EBADMSG;
+		}
+		hdr_size_left -= hdr_size_ext;
+
 		ext_hdr_end = meta_hdr->size + 2;
 		for (i = dev->rd_msg_hdr_count; i < ext_hdr_end; i++) {
 			dev->rd_msg_hdr[i] = mei_read_hdr(dev);
@@ -376,6 +397,12 @@ int mei_irq_read_handler(struct mei_device *dev,
 	}
 
 	if (mei_hdr->dma_ring) {
+		if (hdr_size_left != sizeof(dev->rd_msg_hdr[ext_hdr_end])) {
+			dev_err(dev->dev, "corrupted message header len %d\n",
+				mei_hdr->length);
+			return -EBADMSG;
+		}
+
 		dev->rd_msg_hdr[ext_hdr_end] = mei_read_hdr(dev);
 		dev->rd_msg_hdr_count++;
 		(*slots)--;