Re: [PATCH v3] vsprintf: Prevent crash when dereferencing invalid pointers

Steven Rostedt
2018-03-15T17:01:22Z

On Thu, 15 Mar 2018 17:03:09 +0900
Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> wrote:

> On (03/15/18 16:58), Sergey Senozhatsky wrote:
> > On (03/14/18 15:09), Petr Mladek wrote:
> > [..]
> > > +static const char *check_pointer_access(const void *ptr)
> > > +{
> > > + unsigned char byte;
> > > +
> > > + if (!ptr)
> > > + return "(null)";
> > > +
> > > + if (probe_kernel_read(&byte, ptr, 1))
> > ^^^^^
> > Why one byte? sizeof(ptr)?
>
> I think there is a shorter version - probe_kernel_address(),
> which, seems, was designed for this particular kind of stuff.
>
> void *p;
>
> if (probe_kernel_address(ptr, p))
> ....
>

Agreed.

-- Steve