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)
> {
> struct load_info info = { };
> loff_t size;
> - void *hdr;
> + void *hdr = NULL;
> int err;
>
> 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. :)
--
Kees Cook
