Re: [RFC PATCH] usb: dwc3: ep0: Fix mem corruption on OUT transfers of more than 512 bytes

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Hi,

On Tuesday 09 June 2015 08:09 PM, Michael Trimarchi wrote:
Hi

On Jun 9, 2015 4:36 PM, "Kishon Vijay Abraham I" <kishon@xxxxxx
<mailto:kishon@xxxxxx>> wrote:
 >
 > DWC3 uses bounce buffer to handle non max packet aligned OUT transfers and
 > the size of bounce buffer is 512 bytes. However if the host initiates OUT
 > transfers of size more than 512 bytes (and non max packet aligned), the
 > driver throws a WARN dump but still programs the TRB to receive more than
 > 512 bytes. This will cause bounce buffer to overflow and corrupt the
 > adjacent memory locations which can be fatal.
 >
 > Fix it by programming the TRB to receive a maximum of DWC3_EP0_BOUNCE_SIZE
 > (512) bytes.
 >
 > Signed-off-by: Kishon Vijay Abraham I <kishon@xxxxxx <mailto:kishon@xxxxxx>>
 > ---
 > Steps to see the issue (before this patch)
 > 1) Insert g_zero in DUT
 > 2) run './testusb -t 14 -c 1 -s 520 -v 1' in host (size should be > 512)
 >
 > The test should FAIL since bounce buffer can handle only 512 bytes, but the
 > test PASS. There is a WARN dump in DUT but still there will be memory
 > corruption since the bounce buffer overflows.
 >
 > Tested this patch using USB3 Gen X CV (ch9 tests: usb2 and usb3, link layer
 > testing and MSC tests) and using USB2 X CV (ch9 tests, MSC tests).
 >
 > After the patch, the tests timeout!
 > ./testusb -t 14 -c 1 -s 514 -v 1
 > unknown speed   /dev/bus/usb/001/018    0
 > /dev/bus/usb/001/018 test 14 --> 110 (Connection timed out)
 >
 > IMO a patch to fix this is required for stable releases too. So If this
 > patch is alright, I can post the patch cc'ing stable. While the actual fix
 > would be to have chained TRB, I'm not sure if it can go to stable
 > releases.
 >  drivers/usb/dwc3/ep0.c |   12 ++++++++++--
 >  1 file changed, 10 insertions(+), 2 deletions(-)
 >
 > diff --git a/drivers/usb/dwc3/ep0.c b/drivers/usb/dwc3/ep0.c
 > index 2ef3c8d..8858c60 100644
 > --- a/drivers/usb/dwc3/ep0.c
 > +++ b/drivers/usb/dwc3/ep0.c
 > @@ -816,6 +816,11 @@ static void dwc3_ep0_complete_data(struct dwc3 *dwc,
 >                 unsigned maxp = ep0->endpoint.maxpacket;
 >
 >                 transfer_size += (maxp - (transfer_size % maxp));
 > +
 > +               /* Maximum of DWC3_EP0_BOUNCE_SIZE can only be received */
 > +               if (transfer_size > DWC3_EP0_BOUNCE_SIZE)
 > +                       transfer_size = DWC3_EP0_BOUNCE_SIZE;
 > +

Can you just use maxp in the correct way?

what do you mean by correct way? Using roundup() to calculate transfer_size?

Thanks
Kishon
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