Tested this patch with virtio-net regression tests, everything works fine.
Tested-by: Lei Yang <leiy...@redhat.com>
On Thu, Jul 10, 2025 at 6:44 PM Jason Wang <jasow...@redhat.com> wrote:
>
> On Thu, Jul 10, 2025 at 5:57 PM Paolo Abeni <pab...@redhat.com> wrote:
> >
> > On 7/8/25 4:42 PM, Bui Quang Minh wrote:
> > > Since commit 4959aebba8c0 ("virtio-net: use mtu size as buffer length
> > > for big packets"), the allocated size for big packets is not
> > > MAX_SKB_FRAGS * PAGE_SIZE anymore but depends on negotiated MTU. The
> > > number of allocated frags for big packets is stored in
> > > vi->big_packets_num_skbfrags. This commit fixes the received length
> > > check corresponding to that change. The current incorrect check can lead
> > > to NULL page pointer dereference in the below while loop when erroneous
> > > length is received.
> > >
> > > Fixes: 4959aebba8c0 ("virtio-net: use mtu size as buffer length for big
> > > packets")
> > > Signed-off-by: Bui Quang Minh <minhquangbu...@gmail.com>
> > > ---
> > > Changes in v2:
> > > - Remove incorrect give_pages call
> > > ---
> > > drivers/net/virtio_net.c | 9 ++++++---
> > > 1 file changed, 6 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > > index 5d674eb9a0f2..3a7f435c95ae 100644
> > > --- a/drivers/net/virtio_net.c
> > > +++ b/drivers/net/virtio_net.c
> > > @@ -823,7 +823,7 @@ static struct sk_buff *page_to_skb(struct
> > > virtnet_info *vi,
> > > {
> > > struct sk_buff *skb;
> > > struct virtio_net_common_hdr *hdr;
> > > - unsigned int copy, hdr_len, hdr_padded_len;
> > > + unsigned int copy, hdr_len, hdr_padded_len, max_remaining_len;
> > > struct page *page_to_free = NULL;
> > > int tailroom, shinfo_size;
> > > char *p, *hdr_p, *buf;
> > > @@ -887,12 +887,15 @@ static struct sk_buff *page_to_skb(struct
> > > virtnet_info *vi,
> > > * tries to receive more than is possible. This is usually
> > > * the case of a broken device.
> > > */
> > > - if (unlikely(len > MAX_SKB_FRAGS * PAGE_SIZE)) {
> > > + BUG_ON(offset >= PAGE_SIZE);
> >
> > Minor nit (not intended to block this patch): since you are touching
> > this, you could consider replacing the BUG_ON() with a:
> >
> > if (WARN_ON_ONCE()) <goto error path>.
>
> I'm not sure I get this, but using BUG_ON() can help to prevent bugs
> from being explored.
>
> Thanks
>
> >
> > /P
> >
>
>
