I am not so sure about taking off the cast, just to be in line with patch in 194b3da873fd. The comment can be deleted.
On Wed, May 29, 2019 at 4:35 PM Greg KH <gre...@linuxfoundation.org> wrote: > > On Wed, May 29, 2019 at 12:52:01PM +0800, Young Xiao wrote: > > pg_start is copied from userspace on AGPIOC_BIND and AGPIOC_UNBIND ioctl > > cmds of agp_ioctl() and passed to agpioc_bind_wrap(). As said in the > > comment, (pg_start + mem->page_count) may wrap in case of AGPIOC_BIND, > > and it is not checked at all in case of AGPIOC_UNBIND. As a result, user > > with sufficient privileges (usually "video" group) may generate either > > local DoS or privilege escalation. > > > > See commit 194b3da873fd ("agp: fix arbitrary kernel memory writes") > > for details. > > > > Signed-off-by: Young Xiao <92siuy...@gmail.com> > > --- > > drivers/char/agp/amd64-agp.c | 3 ++- > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/char/agp/amd64-agp.c b/drivers/char/agp/amd64-agp.c > > index c69e39f..5daa0e3 100644 > > --- a/drivers/char/agp/amd64-agp.c > > +++ b/drivers/char/agp/amd64-agp.c > > @@ -60,7 +60,8 @@ static int amd64_insert_memory(struct agp_memory *mem, > > off_t pg_start, int type) > > > > /* Make sure we can fit the range in the gatt table. */ > > /* FIXME: could wrap */ > > - if (((unsigned long)pg_start + mem->page_count) > num_entries) > > + if (((pg_start + mem->page_count) > num_entries) || > > + ((pg_start + mem->page_count) < pg_start)) > > Why did you take off the cast for the first test? > > And if this really does fix this issue, should you remove the FIXME > line? > > thanks, > > greg k-h -- Best regards! Young -----------------------------------------------------------