v5.1-rc1 binder_alloc_do_buffer_copy() BUG_ON triggered by selinux-testsuite

[Todd Kjos]

Paul,

I think this patch will fix it... can you run the selinux-testsuite
with the patch to verify? (the conditional assumed that size_t can go
negative)

Thanks,

-Todd


diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index 9a7c431469b3..bb9a661ffecc 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -2240,7 +2240,8 @@ static size_t binder_get_object(struct binder_proc *proc,
        size_t object_size = 0;

        read_size = min_t(size_t, sizeof(*object), buffer->data_size - offset);
-       if (read_size < sizeof(*hdr) || !IS_ALIGNED(offset, sizeof(u32)))
+       if (offset > buffer->data_size || read_size < sizeof(*hdr) ||
+                       !IS_ALIGNED(offset, sizeof(u32)))
                return 0;
        binder_alloc_copy_from_buffer(&proc->alloc, object, buffer,
                                      offset, read_size);

On Mon, Mar 18, 2019 at 4:02 PM Paul Moore <paul at paul-moore.com> wrote:
>
> On Mon, Mar 18, 2019 at 6:51 PM Todd Kjos <tkjos at google.com> wrote:
> > On Mon, Mar 18, 2019 at 2:31 PM Paul Moore <paul at paul-moore.com> wrote:
> > > Hello all.
> > >
> > > When running the selinux-testsuite (link below) against v5.1-rc1 I hit
> > > the BUG_ON() at the top of binder_alloc_do_buffer_copy() (trace
> > > below).  I'm hoping this is a known issue with a fix already in the
> > > works?
> >
> >
> > Sadly, this is the first report of this, so no fix in flight. I'll try
> > to get a fix up in the next few days.
>
> No problem, thanks for letting me know.  If you need some testing
> help, let me know.
>
> --
> paul moore
> www.paul-moore.com