Re: [PATCH for-4.19(?)] xen/arm: bootfdt: Fix device tree memory node probing

[Julien Grall <julien@xxxxxxx>]

Hi Michal,

On 27/06/2024 13:01, Michal Orzel wrote:
> > > > > +/*
> > > > > + * Check if a node is a proper /memory node according to Devicetree
> > > > > + * Specification v0.4, chapter 3.4.
> > > > > + */
> > > > > +static bool __init device_tree_is_memory_node(const void *fdt, int node,
> > > > > +                                              int depth)
> > > > > +{
> > > > > +    const char *type;
> > > > > +    int len;
> > > > > +
> > > > > +    if ( depth != 1 )
> > > > > +        return false;
> > > > > +
> > > > > +    if ( !device_tree_node_matches(fdt, node, "memory") )
> > > > > +        return false;
> > > > > +
> > > > > +    type = fdt_getprop(fdt, node, "device_type", &len);
> > > > > +    if ( !type )
> > > > > +        return false;
> > > > > +
> > > > > +    if ( (len <= 0) || strcmp(type, "memory") )
> > > > I would consider to use strncmp() to avoid relying on the property to be
> > > > well-formed (i.e. nul-terminated).
> > > Are you sure? AFAIR, libfdt returns NULL and -FDT_ERR_TRUNCATED as len if a 
> > > string is non null terminated.
> > I can't find such code in path. Do you have any pointer?
> I checked and I cannot find such code either. I made the wrong assumption 
> thinking that fdt_getprop can only work with strings.
> Therefore, I'm ok with changing s/strcmp/strncmp/ for hardening. Shall I respin 
> the patch marking it as for-4.20?
Sorry this e-mail fell through the cracks. Yes please. I need to create 
a branch to collect all simple patches for 4.20.
Cheers,

--
Julien Grall