Messages in this thread | | | Date | Wed, 29 May 2019 01:34:59 -0700 | From | Greg KH <> | Subject | Re: [PATCH] amd64-agp: fix arbitrary kernel memory writes |
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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 <92siuyang@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
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