usb: musb: gadget: misplaced out of bounds check

usb: musb: gadget: misplaced out of bounds check

[Bin Liu]

On Thu, Mar 29, 2018 at 06:36:42PM +0200, Greg Kroah-Hartman wrote:
> On Thu, Mar 29, 2018 at 10:48:28AM -0500, Bin Liu wrote:
> > From: Heinrich Schuchardt <xypron.glpk@gmx.de>
> > 
> > musb->endpoints[] has array size MUSB_C_NUM_EPS.
> > We must check array bounds before accessing the array and not afterwards.
> > 
> > Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
> > Signed-off-by: Bin Liu <b-liu@ti.com>
> > ---
> >  drivers/usb/musb/musb_gadget_ep0.c | 14 +++++++++-----
> >  1 file changed, 9 insertions(+), 5 deletions(-)
> 
> Should this also go to the stable kernels?

Your call. My understanding is this is just a potential, and the code
looks wrong - checking the boundary after used it, but the ep index
won't be able to over the boundary anyway. Though I don't have enough
security knowledge to judge if the bug has an security hole...

Regards,
-Bin.
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usb: musb: gadget: misplaced out of bounds check

[Greg Kroah-Hartman]

On Thu, Mar 29, 2018 at 10:48:28AM -0500, Bin Liu wrote:
> From: Heinrich Schuchardt <xypron.glpk@gmx.de>
> 
> musb->endpoints[] has array size MUSB_C_NUM_EPS.
> We must check array bounds before accessing the array and not afterwards.
> 
> Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
> Signed-off-by: Bin Liu <b-liu@ti.com>
> ---
>  drivers/usb/musb/musb_gadget_ep0.c | 14 +++++++++-----
>  1 file changed, 9 insertions(+), 5 deletions(-)

Should this also go to the stable kernels?

thanks,

greg k-h
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usb: musb: gadget: misplaced out of bounds check

[Bin Liu]

From: Heinrich Schuchardt <xypron.glpk@gmx.de>

musb->endpoints[] has array size MUSB_C_NUM_EPS.
We must check array bounds before accessing the array and not afterwards.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Signed-off-by: Bin Liu <b-liu@ti.com>
---
 drivers/usb/musb/musb_gadget_ep0.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/drivers/usb/musb/musb_gadget_ep0.c b/drivers/usb/musb/musb_gadget_ep0.c
index 18da4873e52e..91a5027b5c1f 100644
--- a/drivers/usb/musb/musb_gadget_ep0.c
+++ b/drivers/usb/musb/musb_gadget_ep0.c
@@ -89,15 +89,19 @@ static int service_tx_status_request(
 		}
 
 		is_in = epnum & USB_DIR_IN;
-		if (is_in) {
-			epnum &= 0x0f;
+		epnum &= 0x0f;
+		if (epnum >= MUSB_C_NUM_EPS) {
+			handled = -EINVAL;
+			break;
+		}
+
+		if (is_in)
 			ep = &musb->endpoints[epnum].ep_in;
-		} else {
+		else
 			ep = &musb->endpoints[epnum].ep_out;
-		}
 		regs = musb->endpoints[epnum].regs;
 
-		if (epnum >= MUSB_C_NUM_EPS || !ep->desc) {
+		if (!ep->desc) {
 			handled = -EINVAL;
 			break;
 		}