Re: [PATCH 32/58] isdn/gigaset: Convert timers to use timer_setup()

On Thu, 19 Oct 2017, Paul Bolle wrote:

On Thu, 2017-10-19 at 23:03 +0200, Paul Bolle wrote:

quoted

On Mon, 2017-10-16 at 17:29 -0700, Kees Cook wrote:

quoted

In preparation for unconditionally passing the struct timer_list pointer to
all timer callbacks, switch to using the new timer_setup() and from_timer()
to pass the timer pointer explicitly.

Acked-by: Paul Bolle <redacted>

I have to take this back, sorry!

quoted

For the record: this patch made me nervous but survived the rigorous testing I
threw at it. (Ie, dialing up using bas_gigaset and downloading almost 20 MB in
just over an hour. Whoot! That's more than good enough to ack this patch.)

There was some cleanup I had in mind to make this patch more straightforward.
But that can wait until someone finds a way to hit an issue with this patch.
We'll see.

That someone turns out to be me, doing "modprobe -r bas_gigaset":

<1>[30143.538135] BUG: unable to handle kernel NULL pointer dereference at 000001e9
<1>[30143.538154] IP: mutex_lock+0x19/0x30
<0>[30143.538300]  gigaset_shutdown+0x28/0x130 [gigaset]
<0>[30143.538307]  ? find_module_all+0x62/0x80
<0>[30143.538314]  bas_gigaset_exit+0x31/0x1077 [bas_gigaset]

bas_gigaset_exit()
{
        for (i = 0; i < driver->minors; i++) {
                if (gigaset_shutdown(driver->cs + i) < 0)

gigaset_shutdown(cs)
{
	mutex_lock(&cs->mutex); <-------- Explodes here

So driver->cs + i is invalid. No idea how that might be related to that
timer conversion patch, but ....

Thanks,

	tglx