Hi Baolin, On April 29, 2017 at 5:14, Baolin Wang <baolin.wang@xxxxxxxxxx> wrote: > Hi, > > On 28 April 2017 at 21:26, Bogdan Mirea <Bogdan-Stefan_mirea@xxxxxxxxxx> wrote: > > In the current implementation we get a Kernel Oops when calling rmmod > > for g_serial driver. This happens because the function that creates > > the kthread (gs_console_setup) which should be called at driver > > probing is never called for ttyGS* resulting in a null > > info->console_thread pointer. > > > > Noticed this behaviour on Renesas Rcar-H3 Salvator-X (R8A7795). > > > > Signed-off-by: Bogdan Mirea <Bogdan-Stefan_mirea@xxxxxxxxxx> > > --- > > drivers/usb/gadget/function/u_serial.c | 3 ++- > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/usb/gadget/function/u_serial.c > > b/drivers/usb/gadget/function/u_serial.c > > index e0cd1e4..7283ff5 100644 > > --- a/drivers/usb/gadget/function/u_serial.c > > +++ b/drivers/usb/gadget/function/u_serial.c > > @@ -1256,7 +1256,8 @@ static void gserial_console_exit(void) > > struct gscons_info *info = &gscons_info; > > > > unregister_console(&gserial_cons); > > - kthread_stop(info->console_thread); > > + if (info->console_thread && !IS_ERR(info->console_thread)) > > + kthread_stop(info->console_thread); > > gs_buf_free(&info->con_buf); > > } > > Which kernel version did you test on? Since this issue had been fixed by below patch: > https://www.spinics.net/lists/linux-usb/msg149581.html (usb: gadget: > serial: fix possible Oops caused by calling kthread_stop(NULL)) > > -- > Baolin.wang > Best Regards Thank you for your input! I am using Kernel v4.9 and in this Kernel version the patch[1] is not present, I'm sorry for not checking v4.10. But this patch[1] only covers the case of a NULL pointer and doesn't include the case of a bad pointer value that should also be checked with IS_ERR(info->console_thread). This check is needed since the gserial setup callback function (gs_console_setup()) is only freeing the info->con_buf in the case of kthread_create failure which will result in bad info->console_thread pointer so this will also fail on rmmod if the bad pointer value is not checked in the gserial_console_exit() function before calling kthread_stop(). I think cherry-picking the patch[1] and create a new one that is also checking this bad pointer value case is the best approach. Best Regards, Bogdan [1] https://www.spinics.net/lists/linux-usb/msg149581.html ��.n��������+%������w��{.n�����{���)�� jg��� �����ݢj����G���� ���j:+v���w�m������w�������h�����٥
