From: Eric Dumazet
> Sent: 06 August 2020 23:21
>
> On 7/22/20 11:09 PM, Christoph Hellwig wrote:
> > Rework the remaining setsockopt code to pass a sockptr_t instead of a
> > plain user pointer. This removes the last remaining set_fs(KERNEL_DS)
> > outside of architecture specific code.
> >
> > Signed-off-by: Christoph Hellwig <h...@lst.de>
> > Acked-by: Stefan Schmidt <ste...@datenfreihafen.org> [ieee802154]
> > ---
>
>
> ...
>
> > diff --git a/net/ipv6/raw.c b/net/ipv6/raw.c
> > index 594e01ad670aa6..874f01cd7aec42 100644
> > --- a/net/ipv6/raw.c
> > +++ b/net/ipv6/raw.c
> > @@ -972,13 +972,13 @@ static int rawv6_sendmsg(struct sock *sk, struct
> > msghdr *msg, size_t len)
> > }
> >
>
> ...
>
> > static int do_rawv6_setsockopt(struct sock *sk, int level, int optname,
> > - char __user *optval, unsigned int optlen)
> > + sockptr_t optval, unsigned int optlen)
> > {
> > struct raw6_sock *rp = raw6_sk(sk);
> > int val;
> >
> > - if (get_user(val, (int __user *)optval))
> > + if (copy_from_sockptr(&val, optval, sizeof(val)))
> > return -EFAULT;
> >
>
> converting get_user(...) to copy_from_sockptr(...) really assumed the
> optlen
> has been validated to be >= sizeof(int) earlier.
>
> Which is not always the case, for example here.
>
> User application can fool us passing optlen=0, and a user pointer of exactly
> TASK_SIZE-1
Won't the user pointer force copy_from_sockptr() to call
copy_from_user() which will then do access_ok() on the entire
range and so return -EFAULT.
The only problems arise if the kernel code adds an offset to the
user address.
And the later patch added an offset to the copy functions.
David
-
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