Re: [PATCH] usb: gadget: f_fs: Fix use after free issue as part of queue failure

Greg KH
2020-03-26T09:30:15Z

On Thu, Mar 26, 2020 at 02:14:23PM +0530, Sriharsha Allenki wrote:
> Hi Greg,
>
> On 3/26/2020 1:46 PM, Greg KH wrote:
> > On Thu, Mar 26, 2020 at 11:30:33AM +0530, Sriharsha Allenki wrote:
> >> In AIO case, the request is freed up if ep_queue fails.
> >> However, io_data->req still has the reference to this freed
> >> request. In the case of this failure if there is aio_cancel
> >> call on this io_data it will lead to an invalid dequeue
> >> operation and a potential use after free issue.
> >> Fix this by setting the io_data->req to NULL when the request
> >> is freed as part of queue failure.
> >>
> >> Signed-off-by: Sriharsha Allenki <sallenki@codeaurora.org>
> >> ---
> >> drivers/usb/gadget/function/f_fs.c | 1 +
> >> 1 file changed, 1 insertion(+)
> >>
> >> diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c
> >> index 571917677d35..767f30b86645 100644
> >> --- a/drivers/usb/gadget/function/f_fs.c
> >> +++ b/drivers/usb/gadget/function/f_fs.c
> >> @@ -1120,6 +1120,7 @@ static ssize_t ffs_epfile_io(struct file *file, struct ffs_io_data *io_data)
> >>
> >> ret = usb_ep_queue(ep->ep, req, GFP_ATOMIC);
> >> if (unlikely(ret)) {
> >> + io_data->req = NULL;
> >> usb_ep_free_request(ep->ep, req);
> >> goto error_lock;
> >> }
> >> --
> >> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project
> > What commit does this fix? Should it go to stable kernels, and if so,
> > how far back?
> The commit 2e4c7553cd6f ("usb: gadget: f_fs: add aio support") introduced
> the problem. It is good to have in stable kernels and it needs to go all
> theway back to linux-3.15.y.
>
> Hope this information helps.

Great, please resend this with the proper Fixes: and cc: stable... tag
on it so that it gets picked up properly.

thanks,

greg k-h