[PATCH] Bluetooth: hci_uart: Add a local variable to store the result of h4_recv_buf()

[PATCH] Bluetooth: hci_uart: Add a local variable to store the result of h4_recv_buf()

[Myungho Jung]

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(-)

diff --git a/drivers/bluetooth/hci_h4.c b/drivers/bluetooth/hci_h4.c
index fb97a3bf069b..fa30ec9cebd4 100644
--- a/drivers/bluetooth/hci_h4.c
+++ b/drivers/bluetooth/hci_h4.c
@@ -124,19 +124,22 @@ static const struct h4_recv_pkt h4_recv_pkts[] = {
 static int h4_recv(struct hci_uart *hu, const void *data, int count)
 {
 	struct h4_struct *h4 = hu->priv;
+	struct sk_buff *skb;
 
 	if (!test_bit(HCI_UART_REGISTERED, &hu->flags))
 		return -EUNATCH;
 
-	h4->rx_skb = h4_recv_buf(hu->hdev, h4->rx_skb, data, count,
-				 h4_recv_pkts, ARRAY_SIZE(h4_recv_pkts));
-	if (IS_ERR(h4->rx_skb)) {
-		int err = PTR_ERR(h4->rx_skb);
+	skb = h4_recv_buf(hu->hdev, h4->rx_skb, data, count,
+			  h4_recv_pkts, ARRAY_SIZE(h4_recv_pkts));
+	if (IS_ERR(skb)) {
+		int err = PTR_ERR(skb);
 		bt_dev_err(hu->hdev, "Frame reassembly failed (%d)", err);
 		h4->rx_skb = NULL;
 		return err;
 	}
 
+	h4->rx_skb = skb;
+
 	return count;
 }
 
-- 
2.17.1

Re: [PATCH] Bluetooth: hci_uart: Add a local variable to store the result of h4_recv_buf()

[Marcel Holtmann]

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

Re: [PATCH] Bluetooth: hci_uart: Add a local variable to store the result of h4_recv_buf()

[Myungho Jung]

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

Re: [PATCH] Bluetooth: hci_uart: Add a local variable to store the result of h4_recv_buf()

[Myungho Jung]

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

Re: [PATCH] Bluetooth: hci_uart: Add a local variable to store the result of h4_recv_buf()

[Marcel Holtmann]

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. 

please send a proper patch for this and also don’t forget drivers/bluetooth/h4_recv.h since these two are not yet consolidated.

Regards

Marcel