linux-kernel - [PATCH 4.19 65/89] mt76: fix array overflow on receiving too many fragments for a packet

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Date:   Tue, 17 Mar 2020 11:55:14 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Felix Fietkau <nbd@....name>,
        Kalle Valo <kvalo@...eaurora.org>
Subject: [PATCH 4.19 65/89] mt76: fix array overflow on receiving too many fragments for a packet

From: Felix Fietkau <nbd@....name>

commit b102f0c522cf668c8382c56a4f771b37d011cda2 upstream.

If the hardware receives an oversized packet with too many rx fragments,
skb_shinfo(skb)->frags can overflow and corrupt memory of adjacent pages.
This becomes especially visible if it corrupts the freelist pointer of
a slab page.

Cc: stable@...r.kernel.org
Signed-off-by: Felix Fietkau <nbd@....name>
Signed-off-by: Kalle Valo <kvalo@...eaurora.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/net/wireless/mediatek/mt76/dma.c |    9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

--- a/drivers/net/wireless/mediatek/mt76/dma.c
+++ b/drivers/net/wireless/mediatek/mt76/dma.c
@@ -396,10 +396,13 @@ mt76_add_fragment(struct mt76_dev *dev,
 	struct page *page = virt_to_head_page(data);
 	int offset = data - page_address(page);
 	struct sk_buff *skb = q->rx_head;
+	struct skb_shared_info *shinfo = skb_shinfo(skb);
 
-	offset += q->buf_offset;
-	skb_add_rx_frag(skb, skb_shinfo(skb)->nr_frags, page, offset, len,
-			q->buf_size);
+	if (shinfo->nr_frags < ARRAY_SIZE(shinfo->frags)) {
+		offset += q->buf_offset;
+		skb_add_rx_frag(skb, shinfo->nr_frags, page, offset, len,
+				q->buf_size);
+	}
 
 	if (more)
 		return;