+To: Jiri Pirko
+To: Jakub Kicinski
+CC: David S. Miller
+CC: Eric Dumazet
+CC: Paolo Abeni
+CC: Simon Horman
+CC: netdev@xxxxxxxxxxxxxxx
On 04/02/2025 at 16:44, YAN KANG wrote:
> Dear developers and maintainers,
>
> I found a new kernel NULL-Pointer-Dereference bug titiled "general protection fault in devlink_info_serial_number_put" while using modified syzkaller fuzzing tool. I Itested it on the latest Linux upstream version (6.13.0-rc7)related to ETAS ES58X CAN/USB DRIVER, and it was able to be triggered.
>
> The bug info is:
>
> kernel revision: v6.13-rc7
> OOPS message: general protection fault in devlink_info_serial_number_put
> reproducer:YES
>
> After preliminary analysis, The root casue may be :
> in the function: es58x_devlink_info_get drivers/net/can/usb/etas_es58x/es58x_devlink.c
> es58x_dev->udev->serial == NULL ,but no check for it.
>
> devlink_info_serial_number_put(req, es58x_dev->udev->serial) triggers NPD .
>
> Fix suggestion: Check es58x_dev->udev->serial before deference pointer.
Thanks for the report. I acknowledge the issue: the serial number of a
USB device may be NULL and I forget to check this condition.
@netdev and devlink maintainers
I can of course fix this locally, but this that this kind of issue looks
like some nasty pitfall to me. So, I was wondering if it wouldn't be
safer to add the NULL check in the framework instead of in the device.
The netlink is not part of the hot path, so a NULL check should not have
performance impacts.
I am thinking of:
diff --git a/include/net/netlink.h b/include/net/netlink.h
index e015ffbed819..eaee9a1aa91f 100644
--- a/include/net/netlink.h
+++ b/include/net/netlink.h
@@ -1617,6 +1617,8 @@ static inline int nla_put_sint(struct sk_buff
*skb, int attrtype, s64 value)
static inline int nla_put_string(struct sk_buff *skb, int attrtype,
const char *str)
{
+ if (!str)
+ return 0;
return nla_put(skb, attrtype, strlen(str) + 1, str);
}
Of course, it is also possible to do the check in
devlink_info_serial_number_put().
What do you think?
> If you fix this issue, please add the following tag to the commit:
> Reported-by: yan kang <kangyan91@xxxxxxxxxxx>
> Reported-by: yue sun <samsun1006219@xxxxxxxxx
>
> I hope it helps.
> Best regards
> yan kang
Yours sincerely,
Vincent Mailhol
