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SubjectRE: [PATCH v2] usb: gadget: composite: Fix null pointer exception
Date
> -----Original Message-----
> From: Greg KH <gregkh@linuxfoundation.org>
> Sent: Monday, November 8, 2021 8:56 PM
> To: 胡启航(Nick Hu) <huqihang@oppo.com>
> Cc: balbi@kernel.org; peter.chen@kernel.org; linux-usb@vger.kernel.org;
> linux-kernel@vger.kernel.org
> Subject: Re: [PATCH v2] usb: gadget: composite: Fix null pointer exception
>
> On Mon, Nov 08, 2021 at 12:42:24PM +0000, 胡启航(Nick Hu) wrote:
> > > -----Original Message-----
> > > From: Greg KH <gregkh@linuxfoundation.org>
> > > Sent: Friday, November 5, 2021 8:45 PM
> > > To: 胡启航(Nick Hu) <huqihang@oppo.com>
> > > Cc: balbi@kernel.org; peter.chen@kernel.org;
> > > linux-usb@vger.kernel.org; linux-kernel@vger.kernel.org
> > > Subject: Re: [PATCH v2] usb: gadget: composite: Fix null pointer
> > > exception
> > >
> > > On Fri, Nov 05, 2021 at 06:48:40PM +0800, Qihang Hu wrote:
> > > > In the config_ep_by_speed_and_alt function, select the
> > > > corresponding descriptor through g->speed, but the function driver
> > > > may not support the corresponding speed. So, we need to check
> > > > whether the function driver provides the corresponding speed
> > > > descriptor when selecting the descriptor.
> > > >
> > > > [ 237.708146] android_work: sent uevent USB_STATE=CONNECTED [
> > > > 237.712464] kconfigfs-gadget gadget: super-speed config #1: b [
> > > > 237.712487] kUnable to handle kernel NULL pointer dereference at
> > > virtual address 0000000000000000
> > >
> > > So this is an invalid driver causing this problem? Or can this be
> > > triggered by userspace?
> >
> > Yes, if the kernel is loaded with an interface driver that does not
> > support all speeds, this problem can be triggered in userspace.
>
> What in-kernel driver does not support all speeds that can trigger this?
>
> Why not fix the drivers?

This problem is caused by android f_audio_source.c
I think the core driver code should be improved to make it less susceptible to function-driven influence.
Of course, repairing the function driver is the fundamental solution to the problem.

> > > > [ 237.712493] kMem abort info:
> > > > [ 237.712498] k ESR = 0x96000006 [ 237.712504] k EC = 0x25:
> > > > DABT (current EL), IL = 32 bits [ 237.712510] k SET = 0, FnV =
> > > > 0 [ 237.712515] k EA = 0, S1PTW = 0 [ 237.712520] kData abort
> > > > info:
> > > > [ 237.712525] k ISV = 0, ISS = 0x00000006 [ 237.712530] k CM
> > > > = 0, WnR = 0 [ 237.712536] kuser pgtable: 4k pages, 39-bit VAs,
> > > pgdp=000000020ef29000
> > > > [ 237.712541] k[0000000000000000] pgd=000000020ef2a003,
> > > pud=000000020ef2a003, pmd=0000000000000000
> > > > [ 237.712554] kInternal error: Oops: 96000006 [#1] PREEMPT SMP [
> > > > 237.722067] kSkip md ftrace buffer dump for: 0x1609e0 [
> > > > 237.787037] kWorkqueue: dwc_wq dwc3_bh_work.cfi_jt
> [ 237.854922]
> > > > kpstate: 60c00085 (nZCv daIf +PAN +UAO) [ 237.863165] kpc :
> > > > config_ep_by_speed_and_alt+0x90/0x308
> > > > [ 237.871766] klr : audio_set_alt+0x54/0x78 [ 237.879108] ksp
> > > > : ffffffc0104839e0
> > > >
> > > > Signed-off-by: Qihang Hu <huqihang@oppo.com>
> > >
> > > What commit id does this fix?
> >
> > I have not submitted a BUG.
> > I will study and submit a BUG as soon as possible.
>
> I do not understand what you mean by this. I am asking what commit caused
> this problem so we can mark this one as fixing it.
>

This is a problem with Android's driver code.
The kernel does not include it.

Thanks

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