Re: [PATCH v3 6/9] bus: mhi: core: WARN_ON for malformed vector table

[bbhatt]

On 2020-04-30 08:02, Jeffrey Hugo wrote:
> On 4/29/2020 2:52 PM, Bhaumik Bhatt wrote:
> > Add a bounds check in the firmware copy routine to exit if a malformed
> > vector table is found while attempting to load the firmware in to the
> > BHIe vector table.
> >
> > Signed-off-by: Bhaumik Bhatt <bbhatt@xxxxxxxxxxxxxx>
> > ---
> >   drivers/bus/mhi/core/boot.c | 6 ++++++
> >   1 file changed, 6 insertions(+)
> >
> > diff --git a/drivers/bus/mhi/core/boot.c b/drivers/bus/mhi/core/boot.c
> > index 17c636b..bc70edc 100644
> > --- a/drivers/bus/mhi/core/boot.c
> > +++ b/drivers/bus/mhi/core/boot.c
> > @@ -362,8 +362,14 @@ static void mhi_firmware_copy(struct 
> > mhi_controller *mhi_cntrl,
> >   	int i = 0;
> >   	struct mhi_buf *mhi_buf = img_info->mhi_buf;
> >   	struct bhi_vec_entry *bhi_vec = img_info->bhi_vec;
> > +	struct device *dev = &mhi_cntrl->mhi_dev->dev;
> >     	while (remainder) {
> > +		if (WARN_ON(i >= img_info->entries)) {
> > +			dev_err(dev, "Malformed vector table\n");
>
> I feel like this message needs more detail.  At a minimum, I think it
> should indicate what vector table (BHIe).  I think if you can identify
> what file, etc the the glitch is in, that would be better.  Maybe some
> detail about i and img_info->entries.
>
> If I see this error message, I should have enough information to
> immediately debug the issue.  If it tells enough to go directly into
> the firmware file and have a look at entry X to see what might be
> corrupt about it, that makes my debugging very efficient.  If I have
> to go back to the code to figure out what "Malformed vector table"
> means, and then maybe apply a patch to get more data about the error -
> the error message is not as useful as it should be.

I plan on dropping this patch as it looks like an unnecessary check 
since we
will always rely on the firmware->size from the request_firmware() API 
in order
to calculate the img_info->entries (or we can call it the number of 
segments, in
our case). And we will never fail in the if loop as values will already 
be
bounded.

> > +			return;
> > +		}
> > +
> >   		to_cpy = min(remainder, mhi_buf->len);
> >   		memcpy(mhi_buf->buf, buf, to_cpy);
> >   		bhi_vec->dma_addr = mhi_buf->dma_addr;