Re: [PATCH 1/3] module: Invalidate signatures on force-loaded modules

[Ben Hutchings]

On Tue, 2016-04-26 at 20:07 +0930, Rusty Russell wrote:
> Ben Hutchings <ben@xxxxxxxxxxxxxxx> writes:
> > 
> > Signing a module should only make it trusted by the specific kernel it
> > was built for, not anything else.ÂÂLoading a signed module meant for a
> > kernel with a different ABI could have interesting effects.
> > Therefore, treat all signatures as invalid when a module is
> > force-loaded.
> > 
> > Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
> > Cc: stable@xxxxxxxxxxxxxxx
> > ---
> > Âkernel/module.c | 13 +++++++++----
> > Â1 file changed, 9 insertions(+), 4 deletions(-)
> > 
> > diff --git a/kernel/module.c b/kernel/module.c
> > index 66426f743c29..649b1827ed15 100644
> > --- a/kernel/module.c
> > +++ b/kernel/module.c
> > @@ -2599,13 +2599,18 @@ static inline void kmemleak_load_module(const struct module *mod,
> > Â#endif
> > Â
> > Â#ifdef CONFIG_MODULE_SIG
> > -static int module_sig_check(struct load_info *info)
> > +static int module_sig_check(struct load_info *info, int flags)
> > Â{
> > Â	int err = -ENOKEY;
> > Â	const unsigned long markerlen = sizeof(MODULE_SIG_STRING) - 1;
> > Â	const void *mod = info->hdr;
> > Â
> > -	if (info->len > markerlen &&
> > +	/*
> > +	Â* Require flags == 0, as a module with version information
> > +	Â* removed is no longer the module that was signed
> > +	Â*/
> > +	if (flags == 0 &&
> This check is a bit lazy.ÂÂWe could have other flags in future,
> so this should really be !(flags &
> (MODULE_INIT_IGNORE_MODVERSIONS|MODULE_INIT_IGNORE_VERMAGIC) right?

Yes we could, but I'd prefer this to fail-safe in case no-one thinks
about whether it should be updated then.

Ben.

-- 
Ben Hutchings
The generation of random numbers is too important to be left to chance.
                                                            - Robert Coveyou

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