Re: [PATCH] net: fec: Fixed panic problem with non-tso

[Eric Dumazet]

On Tue, 2017-01-17 at 20:21 -0800, Eric Dumazet wrote:
> On Wed, 2017-01-18 at 03:12 +0000, Ashizuka, Yuusuke wrote:
> 
> > indeed.
> > 
> > In the case of TSO with i.MX6 system (highmem enabled) with 2GB memory,
> > "this_frag->page.p" did not become highmem area.
> > (We confirmed by transferring about 100MB of files)
> > 
> > However, in the case of non-tso on an i.MX6 system with 2GB of memory,
> > "this_frag->page.p" may become a highmem area.
> > (Occurred with approximately 2MB of file transfer)
> > 
> > For non-tso only, I do not know the reason why "this_frag-> page.p" 
> > in this driver shows highmem area.
> 
> This worries me, since this driver does not set NETIF_F_HIGHDMA in its
> features.
> 
> No packet should be given to this driver with a highmem fragment
> 
> Check is done in illegal_highdma() in net/core/dev.c

This used to work.

I suspect commit ec5f061564238892005257c83565a0b58ec79295
("net: Kill link between CSUM and SG features.")

added this bug.

Can you try this hot fix :

diff --git a/net/core/dev.c b/net/core/dev.c
index 
ad5959e561166f445bdd9d7260652a338f74cfea..073b832b945257dba9ed47f4bf875605225effc9
 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2773,9 +2773,9 @@ static netdev_features_t harmonize_features(struct 
sk_buff *skb,
        if (skb->ip_summed != CHECKSUM_NONE &&
            !can_checksum_protocol(features, type)) {
                features &= ~(NETIF_F_CSUM_MASK | NETIF_F_GSO_MASK);
-       } else if (illegal_highdma(skb->dev, skb)) {
-               features &= ~NETIF_F_SG;
        }
+       if (illegal_highdma(skb->dev, skb))
+               features &= ~NETIF_F_SG;
 
        return features;
 }