[PATCH v1] mmc: fix signed vs unsigned compare in read check in _spl_load()

[Franco VENTURI]

Sean, thanks for the quick response.

I just resubmitted version 2 of that patch with a cast to int.

Franco


> On 07/31/2024 8:52 AM EDT Sean Anderson <seanga2 at gmail.com> wrote:
> 
>  
> Hi Franco,
> 
> On 7/30/24 09:30, Franco Venturi wrote:
> > Fix signed vs unsigned compare in read check in _spl_load()
> > 
> > Issue: when info->read() returns a negative value because of an error,
> >         the comparison of 'read' (signed) with 'sizeof(*header)'
> >         (unsigned silently converts the negative value into a very
> >         large unsigned value and the check on the error condition
> >         always return false, i.e. the error is not detected
> > Symptoms: if spl_load_image_fat() is unable to find the file 'uImage',
> >            the SPL phase of the boot process just hangs after displaying
> >            the following line:
> >            Trying to boot from MMC1
> > Fix: first check if 'read' is negative then check its value against
> >       'sizeof(*header)'
> > Reference: https://stackoverflow.com/questions/17293749/sizeof-operator-in-if-statement
> > 
> > Signed-off-by: Franco Venturi <fventuri at comcast.net>
> > ---
> > 
> >   include/spl_load.h | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/include/spl_load.h b/include/spl_load.h
> > index 1c2b296c0a..1e05599d29 100644
> > --- a/include/spl_load.h
> > +++ b/include/spl_load.h
> > @@ -22,7 +22,7 @@ static inline int _spl_load(struct spl_image_info *spl_image,
> >   
> >   	read = info->read(info, offset, ALIGN(sizeof(*header),
> >   					      spl_get_bl_len(info)), header);
> > -	if (read < sizeof(*header))
> > +	if (read < 0 || read < sizeof(*header))
> >   		return -EIO;
> >   
> >   	if (image_get_magic(header) == FDT_MAGIC) {
> 
> Since read and int and sizeof(*header) < INT_MAX, I think the best solution is
> to cast the latter to an int.
> 
> --Sean