Re: [PATCH 2/4] fs: Remove FIRMWARE_PREALLOC_BUFFER from kernel_read_file() enums

[Scott Branden]

Hi Kees

On 2020-07-10 3:44 p.m., Kees Cook wrote:
> On Fri, Jul 10, 2020 at 03:10:25PM -0700, Scott Branden wrote:
> > On 2020-07-10 3:04 p.m., Matthew Wilcox wrote:
> > > On Fri, Jul 10, 2020 at 02:00:32PM -0700, Scott Branden wrote:
> > > > > @@ -950,8 +951,8 @@ int kernel_read_file(struct file *file, void **buf, loff_t *size,
> > > > >     		goto out;
> > > > >     	}
> > > > > -	if (id != READING_FIRMWARE_PREALLOC_BUFFER)
> > > > > -		*buf = vmalloc(i_size);
> > > > > +	if (!*buf)
> > > > The assumption that *buf is always NULL when id !=
> > > > READING_FIRMWARE_PREALLOC_BUFFER doesn't appear to be correct.
> > > > I get unhandled page faults due to this change on boot.
> > > Did it give you a stack backtrace?
> > Yes, but there's no requirement that *buf need to be NULL when calling this
> > function.
> > To fix my particular crash I added the following locally:
> >
> > --- a/kernel/module.c
> > +++ b/kernel/module.c
> > @@ -3989,7 +3989,7 @@ SYSCALL_DEFINE3(finit_module, int, fd, const char
> > __user *, uargs, int, flags)
> >  Â{
> >  ÂÂÂÂ struct load_info info = { };
> >  ÂÂÂÂ loff_t size;
> > -ÂÂÂ void *hdr;
> > +ÂÂÂ void *hdr = NULL;
> >  ÂÂÂÂ int err;
> >
> >  ÂÂÂÂ err = may_init_module();
> Thanks for the diagnosis and fix! I haven't had time to cycle back
> around to this series yet. Hopefully soon. :)
In order to assist in your patchset I have combined it with my patch 
series here:
https://github.com/sbranden/linux/tree/kernel_read_file_for_kees

Please let me know if this matches your expectations for my patches or 
if there is something else I need to change.

Thanks,
Scott