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Message-ID: <2024022302-routine-schematic-b4fd@gregkh>
Date: Fri, 23 Feb 2024 06:58:09 +0100
From: Greg KH <gregkh@...uxfoundation.org>
To: Selvarasu Ganesan <quic_selvaras@...cinc.com>
Cc: brauner@...nel.org, axboe@...nel.dk, jack@...e.cz, jlayton@...nel.org,
keescook@...omium.org, peter@...sgaard.com, hayama@...eo.co.jp,
dmantipov@...dex.ru, quic_linyyuan@...cinc.com,
linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
quic_ppratap@...cinc.com, quic_wcheng@...cinc.com,
quic_jackp@...cinc.com
Subject: Re: [PATCH] usb: gadget: f_fs: Fix NULL pointer dereference in
ffs_epfile_async_io_complete()
On Thu, Feb 22, 2024 at 09:48:09PM -0800, Selvarasu Ganesan wrote:
> In scenarios of continuous and parallel usage of multiple FFS interfaces
> and concurrent adb operations (e.g., adb root, adb reboot), there's a
> chance that ffs_epfile_async_io_complete() might be processed after
> ffs_epfile_release(). This could lead to a NULL pointer dereference of
> ffs when accessing the ffs pointer in ffs_epfile_async_io_complete(), as
> ffs is freed as part of ffs_epfile_release(). This epfile release is
> part of file operation and is triggered when user space daemons restart
> themselves or a reboot is initiated.
>
> Fix this issue by adding a NULL pointer check for ffs in
> ffs_epfile_async_io_complete().
>
> [ 9981.393115] Unable to handle kernel NULL pointer dereference at virtual address 00000000000001e0
> [ 9981.402854] Mem abort info:
> ...
> [ 9981.532540] Hardware name: Qualcomm Technologies,
> [ 9981.540579] pstate: 204000c5 (nzCv daIF +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> [ 9981.548438] pc : ffs_epfile_async_io_complete+0x38/0x4c
> [ 9981.554529] lr : usb_gadget_giveback_request+0x30/0xd0
> ...
> [ 9981.645057] Call trace:
> [ 9981.648282] ffs_epfile_async_io_complete+0x38/0x4c
> [ 9981.654004] usb_gadget_giveback_request+0x30/0xd0
> [ 9981.659637] dwc3_gadget_endpoint_trbs_complete+0x1a8/0x48c
> [ 9981.666074] dwc3_process_event_entry+0x378/0x648
> [ 9981.671622] dwc3_process_event_buf+0x6c/0x288
> [ 9981.676903] dwc3_thread_interrupt+0x3c/0x68
> [ 9981.682003] irq_thread_fn+0x2c/0x8c
> [ 9981.686388] irq_thread+0x198/0x2ac
> [ 9981.690685] kthread+0x154/0x218
> [ 9981.694717] ret_from_fork+0x10/0x20
>
> Signed-off-by: Selvarasu Ganesan <quic_selvaras@...cinc.com>
What commit id does this fix? Should it go to stable kernels?
> ---
> drivers/usb/gadget/function/f_fs.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c
> index be3851cffb73..d8c8e88628f9 100644
> --- a/drivers/usb/gadget/function/f_fs.c
> +++ b/drivers/usb/gadget/function/f_fs.c
> @@ -849,7 +849,9 @@ static void ffs_epfile_async_io_complete(struct usb_ep *_ep,
> usb_ep_free_request(_ep, req);
>
> INIT_WORK(&io_data->work, ffs_user_copy_worker);
> - queue_work(ffs->io_completion_wq, &io_data->work);
> +
> + if (ffs && ffs->io_completion_wq)
> + queue_work(ffs->io_completion_wq, &io_data->work);
What happens if ffs->io_compleation_wq goes away right after you test
it but before you call queue_work()?
Where is the locking here to prevent that?
thanks,
greg k-h
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