RE: [PATCH] usb: uvc: Fix 1-byte out-of-bounds read in uvc_parse_format()

[yjjuny.lee]

The buffer length check before calling uvc_parse_format() only ensured
that the buffer has at least 3 bytes (buflen > 2), buf the function
accesses buffer[3], requiring at least 4 bytes.

This can lead to an out-of-bounds read if the buffer has exactly 3 bytes.

Fix it by checking that the buffer has at least 4 bytes in
uvc_parse_format().

Signed-off-by: Youngjun Lee <yjjuny.lee@xxxxxxxxxxx>
Reviewed-by: Ricardo Ribalda <ribalda@xxxxxxxxxxxx>
Reviewed-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
---
 drivers/media/usb/uvc/uvc_driver.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c
index da24a655ab68..1100469a83a2 100644
--- a/drivers/media/usb/uvc/uvc_driver.c
+++ b/drivers/media/usb/uvc/uvc_driver.c
@@ -344,6 +344,9 @@ static int uvc_parse_format(struct uvc_device *dev,
 	u8 ftype;
 	int ret;
 
+	if (buflen < 4)
+		return -EINVAL;
+
 	format->type = buffer[2];
 	format->index = buffer[3];
 	format->frames = frames;
-- 
2.43.0


> On Tue, Jun 10, 2025 at 02:58:25PM +0200, Ricardo Ribalda wrote:
> > Hi Youngjun
> > 
> > You still miss the v2 (v3 in this case). and the trailers.
> > 
> > In the future you can use the b4 tool to take care of most of the details.
> > https://b4.docs.kernel.org/en/latest/contributor/overview.html
> > It has "dry-run" option that let you review the mails before you send 
> > them to the mailing list
> > 
> > Please do not resubmit a new patch to fix this, only send a new patch 
> > to fix more comments for other people.
> > 
> > Regards!
> > 
> > On Tue, 10 Jun 2025 at 14:41, Youngjun Lee <yjjuny.lee@xxxxxxxxxxx> wrote:
> > >
> > > The buffer length check before calling uvc_parse_format() only 
> > > ensured that the buffer has at least 3 bytes (buflen > 2), buf the 
> > > function accesses buffer[3], requiring at least 4 bytes.
> > >
> > > This can lead to an out-of-bounds read if the buffer has exactly 3 bytes.
> > >
> > > Fix it by checking that the buffer has at least 4 bytes in 
> > > uvc_parse_format().
> >
> > Fixes: c0efd232929c ("V4L/DVB (8145a): USB Video Class driver")
> > Cc: stable@xxxxxxxxxxxxxxx
> > Reviewed-by: Ricardo Ribalda <ribalda@xxxxxxxxxxxx>
>
> Reviewed-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
>
> > > Signed-off-by: Youngjun Lee <yjjuny.lee@xxxxxxxxxxx>
> > > ---
> > >  drivers/media/usb/uvc/uvc_driver.c | 3 +++
> > >  1 file changed, 3 insertions(+)
> > >
> > > diff --git a/drivers/media/usb/uvc/uvc_driver.c 
> > > b/drivers/media/usb/uvc/uvc_driver.c
> > > index da24a655ab68..1100469a83a2 100644
> > > --- a/drivers/media/usb/uvc/uvc_driver.c
> > > +++ b/drivers/media/usb/uvc/uvc_driver.c
> > > @@ -344,6 +344,9 @@ static int uvc_parse_format(struct uvc_device *dev,
> > >         u8 ftype;
> > >         int ret;
> > >
> > > +       if (buflen < 4)
> > > +               return -EINVAL;
> > > +
> > >         format->type = buffer[2];
> > >         format->index = buffer[3];
> > >         format->frames = frames;

--
Thanks & Regards,

Youngjun Lee