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From:   Peilin Ye <yepeilin.cs@gmail.com>
To:     Marcel Holtmann <marcel@holtmann.org>,
        Johan Hedberg <johan.hedberg@gmail.com>
Cc:     Peilin Ye <yepeilin.cs@gmail.com>,
        "David S . Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Russell King <linux@armlinux.org.uk>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-bluetooth@vger.kernel.org, netdev@vger.kernel.org,
        syzkaller-bugs@googlegroups.com,
        linux-kernel-mentees@lists.linuxfoundation.org,
        linux-kernel@vger.kernel.org
Subject: [Linux-kernel-mentees] [PATCH v3] net/bluetooth: Fix slab-out-of-bounds read in hci_extended_inquiry_result_evt()
Date:   Fri, 10 Jul 2020 12:09:15 -0400
Message-Id: <20200710160915.228980-1-yepeilin.cs@gmail.com>
In-Reply-To: <20200709130224.214204-1-yepeilin.cs@gmail.com>
References: <20200709130224.214204-1-yepeilin.cs@gmail.com>
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Check upon `num_rsp` is insufficient. A malformed event packet with a
large `num_rsp` number makes hci_extended_inquiry_result_evt() go out
of bounds. Fix it.

This patch fixes the following syzbot bug:

    https://syzkaller.appspot.com/bug?id=4bf11aa05c4ca51ce0df86e500fce486552dc8d2

Reported-by: syzbot+d8489a79b781849b9c46@syzkaller.appspotmail.com
Cc: stable@vger.kernel.org
Signed-off-by: Peilin Ye <yepeilin.cs@gmail.com>
---
Change in v3:
    - Minimum `skb->len` requirement was 1 byte inaccurate since `info`
      starts from `skb->data + 1`. Fix it.

Changes in v2:
    - Use `skb->len` instead of `skb->truesize` as the length limit.
    - Leave `num_rsp` as of type `int`.

 net/bluetooth/hci_event.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
index 03a0759f2fc2..13d8802b8137 100644
--- a/net/bluetooth/hci_event.c
+++ b/net/bluetooth/hci_event.c
@@ -4375,7 +4375,7 @@ static void hci_extended_inquiry_result_evt(struct hci_dev *hdev,
 
 	BT_DBG("%s num_rsp %d", hdev->name, num_rsp);
 
-	if (!num_rsp)
+	if (!num_rsp || skb->len < num_rsp * sizeof(*info) + 1)
 		return;
 
 	if (hci_dev_test_flag(hdev, HCI_PERIODIC_INQ))
-- 
2.25.1