On Thu, Feb 29, 2024 at 10:59:10PM -0800, Jakub Kicinski wrote: > On Thu, 29 Feb 2024 13:30:22 -0800 Kees Cook wrote: > > Introduce a new struct net_device_priv that contains struct net_device > > but also accounts for the commonly trailing bytes through the "size" and > > "data" members. > > I'm a bit unclear on the benefit. Perhaps I'm unaccustomed to "safe C". > > > As many dummy struct net_device instances exist still, > > it is non-trivial to but this flexible array inside struct net_device > > put > > Non-trivial, meaning what's the challenge? > We also do somewhat silly things with netdev lifetime, because we can't > assume netdev gets freed by netdev_free(). Cleaning up the "embedders" > would be beneficial for multiple reasons. > > > itself. But we can add a sanity check in netdev_priv() to catch any > > attempts to access the private data of a dummy struct. > > > > Adjust allocation logic to use the new full structure. > > > > Signed-off-by: Kees Cook <keesc...@chromium.org> > > > diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h > > index 118c40258d07..b476809d0bae 100644 > > --- a/include/linux/netdevice.h > > +++ b/include/linux/netdevice.h > > @@ -1815,6 +1815,8 @@ enum netdev_stat_type { > > NETDEV_PCPU_STAT_DSTATS, /* struct pcpu_dstats */ > > }; > > > > +#define NETDEV_ALIGN 32 > > Unless someone knows what this is for it should go. > Align priv to cacheline size. > > > /** > > * struct net_device - The DEVICE structure. > > * > > > @@ -2665,7 +2673,14 @@ void dev_net_set(struct net_device *dev, struct net > > *net) > > */ > > static inline void *netdev_priv(const struct net_device *dev) > > { > > - return (char *)dev + ALIGN(sizeof(struct net_device), NETDEV_ALIGN); > > + struct net_device_priv *priv; > > + > > + /* Dummy struct net_device have no trailing data. */ > > + if (WARN_ON_ONCE(dev->reg_state == NETREG_DUMMY)) > > + return NULL; > > This is a static inline with roughly 11,000 call sites, according to > a quick grep. Aren't WARN_ONCE() in static inlines creating a "once" > object in every compilation unit where they get used?
It also, if this every trips, will reboot the box for those that run with panic-on-warn set, is that something that you all really want? thanks, greg k-h