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SubjectPossible null pointer dereference in isp1760.ko
Date
Hello.

While searching for races in the Linux kernel I've come across
"drivers/usb/isp1760/isp1760.ko" module. Here is a question that I came
up with while analyzing results. Lines are given using the info from
Linux v4.12.

Consider the following case:

Thread 1: Thread 2:
isp1760_plat_probe
-> isp1760_register
-> isp1760_udc_register
request_irq(...,udc)
-> isp1760_udc_init_eps(udc) isp1760_udc_irq
for(i = 0; ...){ for(i = 0; ...) {
ep = &udc->ep[i] ep = &udc->ep[i%2]
-> isp1760_ep_rx_ready(ep)
INIT_LIST_HEAD(ep->queue) list_empty(&ep->queue)
(isp1760-udc.c: line 1367) (isp1760-udc.c: line 303)

As far as I understand ep->queue is NULL before its initialization in
isp1760_udc_init_eps and list_empty() tries to access the '->next'
pointer member of the passed parameter.

Is this case possible from your point of view?

Thank you for your time.

-- Anton Volkov
Linux Verification Center, ISPRAS
web: http://linuxtesting.org
e-mail: avolkov@ispras.ru

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