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Date:   Sun, 20 Jan 2019 01:45:00 -0800
From:   Myungho Jung <mhjungk@gmail.com>
To:     Marcel Holtmann <marcel@holtmann.org>
Cc:     Johan Hedberg <johan.hedberg@gmail.com>,
        linux-bluetooth@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] Bluetooth: hci_uart: Add a local variable to store the
 result of h4_recv_buf()
Message-ID: <20190120094459.GA22129@myunghoj-Precision-5530>
References: <20190111065514.GA26542@myunghoj-Precision-5530>
 <09FCB21A-2184-4CDB-8BF0-75C403DF39F9@holtmann.org>
 <20190119081919.GA10681@myunghoj-Precision-5530>
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On Sat, Jan 19, 2019 at 12:19:20AM -0800, Myungho Jung wrote:
> On Fri, Jan 18, 2019 at 10:19:41AM +0100, Marcel Holtmann wrote:
> > Hi Myungho,
> > 
> > > In h4_recv(), if h4_recv_buf() returns error and h4_recv() is
> > > asynchronously called again before setting rx_skb to NULL, ERR_PTR will
> > > be dereferenced in h4_recv_buf(). Check return value in a local variable
> > > before writing to rx_skb.
> > > 
> > > Reported-by: syzbot+017a32f149406df32703@syzkaller.appspotmail.com
> > > Signed-off-by: Myungho Jung <mhjungk@gmail.com>
> > > ---
> > > drivers/bluetooth/hci_h4.c | 11 +++++++----
> > > 1 file changed, 7 insertions(+), 4 deletions(-)
> > 
> > patch has been applied to bluetooth-next tree.
> > 
> > Can you actually fix all callers of h4_recv_buf since they all suffer from the same issue.
> > 
> > Regards
> > 
> > Marcel
> > 
> 
> Hi Marcel,
> 
> Sure, let me check other callers and fix them if applicable.
> 
> Thanks,
> Myungho
> 

Hi Marcel,

I found there are many callers that need to be fixed. So, how about checking
error code in h4_recv_buf() instead?

diff --git a/drivers/bluetooth/hci_h4.c b/drivers/bluetooth/hci_h4.c
index fb97a3bf069b..dea48090d2dc 100644
--- a/drivers/bluetooth/hci_h4.c
+++ b/drivers/bluetooth/hci_h4.c
@@ -174,6 +174,10 @@ struct sk_buff *h4_recv_buf(struct hci_dev *hdev, struct sk_buff *skb,
 	struct hci_uart *hu = hci_get_drvdata(hdev);
 	u8 alignment = hu->alignment ? hu->alignment : 1;
 
+	/* Check if socket buffer is not reset yet from previous error */
+	if (IS_ERR(skb))
+		skb = NULL;
+
 	while (count) {
 		int i, len;


It is tested and verified by syzbot. The previous commit is no more needed if
this looks better. 

Thanks,
Myungho