From: Jim Baxter <[email protected]>
"Unable to handle kernel NULL pointer dereference at virtual address
00000078" is reported with "PC is at eth_start_xmit+0x19c/0x378 [u_ether]"
The failure scenario is seen when closing the NCM connection while the
TCP/IPv6 stack is still trying to transmit over NCM.
Defensive code is missing from commit
6d3865f9d41f15ddbcecaa6722871fc0db21d7ab
"usb: gadget: NCM: Add transmit multi-frame."
Add check for non-NULL dev->port_usb before accessing
dev->port_usb->supports_multi_frame.
Signed-off-by: Mark Craske <[email protected]>
Signed-off-by: Jim Baxter <[email protected]>
---
drivers/usb/gadget/function/u_ether.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/usb/gadget/function/u_ether.c b/drivers/usb/gadget/function/u_ether.c
index 637809e..68f0b7b 100644
--- a/drivers/usb/gadget/function/u_ether.c
+++ b/drivers/usb/gadget/function/u_ether.c
@@ -556,7 +556,8 @@ static netdev_tx_t eth_start_xmit(struct sk_buff *skb,
/* Multi frame CDC protocols may store the frame for
* later which is not a dropped frame.
*/
- if (dev->port_usb->supports_multi_frame)
+ if (dev->port_usb &&
+ dev->port_usb->supports_multi_frame)
goto multiframe;
goto drop;
}
--
1.9.1
On Mon, 25 Apr 2016 16:25:03 +0100
<[email protected]> wrote:
> From: Jim Baxter <[email protected]>
>
> "Unable to handle kernel NULL pointer dereference at virtual address
> 00000078" is reported with "PC is at eth_start_xmit+0x19c/0x378 [u_ether]"
>
> The failure scenario is seen when closing the NCM connection while the
> TCP/IPv6 stack is still trying to transmit over NCM.
>
> Defensive code is missing from commit
> 6d3865f9d41f15ddbcecaa6722871fc0db21d7ab
> "usb: gadget: NCM: Add transmit multi-frame."
This looks inadequate. Surely you also need to hold dev->lock ?
Also it'll also crash at the no zlp test with the same problem.
Alan