| Message ID | 20241220083741.175329-1-kory.maincent@bootlin.com (mailing list archive) |
|---|---|
| State | New |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [net-next,v2] net: ethtool: Fix suspicious rcu_dereference usage | expand |
On Fri, Dec 20, 2024 at 9:37 AM Kory Maincent <kory.maincent@bootlin.com> wrote: > > The __ethtool_get_ts_info function can be called with or without the > rtnl lock held. When the rtnl lock is not held, using rtnl_dereference() > triggers a warning due to the lack of lock context. > > Add an rcu_read_lock() to ensure the lock is acquired and to maintain > synchronization. > > Reported-by: syzbot+a344326c05c98ba19682@syzkaller.appspotmail.com > Closes: https://lore.kernel.org/netdev/676147f8.050a0220.37aaf.0154.GAE@google.com/ > Fixes: b9e3f7dc9ed9 ("net: ethtool: tsinfo: Enhance tsinfo to support several hwtstamp by net topology") > Signed-off-by: Kory Maincent <kory.maincent@bootlin.com> > --- Reviewed-by: Eric Dumazet <edumazet@google.com>
diff --git a/net/ethtool/common.c b/net/ethtool/common.c index 02f941f667dd..2607aea1fbfb 100644 --- a/net/ethtool/common.c +++ b/net/ethtool/common.c @@ -870,7 +870,8 @@ int __ethtool_get_ts_info(struct net_device *dev, { struct hwtstamp_provider *hwprov; - hwprov = rtnl_dereference(dev->hwprov); + rcu_read_lock(); + hwprov = rcu_dereference(dev->hwprov); /* No provider specified, use default behavior */ if (!hwprov) { const struct ethtool_ops *ops = dev->ethtool_ops; @@ -887,9 +888,11 @@ int __ethtool_get_ts_info(struct net_device *dev, info->so_timestamping |= SOF_TIMESTAMPING_RX_SOFTWARE | SOF_TIMESTAMPING_SOFTWARE; + rcu_read_unlock(); return err; } + rcu_read_unlock(); return ethtool_get_ts_info_by_phc(dev, info, &hwprov->desc); }
The __ethtool_get_ts_info function can be called with or without the rtnl lock held. When the rtnl lock is not held, using rtnl_dereference() triggers a warning due to the lack of lock context. Add an rcu_read_lock() to ensure the lock is acquired and to maintain synchronization. Reported-by: syzbot+a344326c05c98ba19682@syzkaller.appspotmail.com Closes: https://lore.kernel.org/netdev/676147f8.050a0220.37aaf.0154.GAE@google.com/ Fixes: b9e3f7dc9ed9 ("net: ethtool: tsinfo: Enhance tsinfo to support several hwtstamp by net topology") Signed-off-by: Kory Maincent <kory.maincent@bootlin.com> --- I did not manage to reproduce the issue even with the c repro file from syzbot. The c repro run well on my board. Maybe I missed CONFIG being enabled other than PROVE_LOCKING and PROVE_RCU. I assume this will fix it only by looking at the code. Changes in v2: - Add rcu_read_lock() --- net/ethtool/common.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)