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SubjectRe: [PATCHv2 net] bonding: fix missed rcu protection
On Tue, May 17, 2022 at 01:32:58PM -0400, Jonathan Toppins wrote:
> Signed-off-by: Jonathan Toppins <jtoppins@redhat.com>
> ---
> RESEND, list still didn't receive my last version
>
> The diffstat is slightly larger but IMO a slightly more readable version.
> When I was reading v2 I found myself jumping around.

Hi Jon,

Thanks for the commit. But..

> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
> index 38e152548126..f9d27b63c454 100644
> --- a/drivers/net/bonding/bond_main.c
> +++ b/drivers/net/bonding/bond_main.c
> @@ -5591,23 +5591,32 @@ static int bond_ethtool_get_ts_info(struct net_device *bond_dev,
> const struct ethtool_ops *ops;
> struct net_device *real_dev;
> struct phy_device *phydev;
> + int ret = 0;
>
> + rcu_read_lock();
> real_dev = bond_option_active_slave_get_rcu(bond);
> - if (real_dev) {
> - ops = real_dev->ethtool_ops;
> - phydev = real_dev->phydev;
> -
> - if (phy_has_tsinfo(phydev)) {
> - return phy_ts_info(phydev, info);
> - } else if (ops->get_ts_info) {
> - return ops->get_ts_info(real_dev, info);
> - }
> - }
> + if (real_dev)
> + dev_hold(real_dev);
> + rcu_read_unlock();
> +
> + if (!real_dev)
> + goto software;
>
> + ops = real_dev->ethtool_ops;
> + phydev = real_dev->phydev;
> +
> + if (phy_has_tsinfo(phydev))
> + ret = phy_ts_info(phydev, info);
> + else if (ops->get_ts_info)
> + ret = ops->get_ts_info(real_dev, info);
else {
dev_put(real_dev);
goto software;
}

Here we need another check and goto software if !phy_has_tsinfo() and
no ops->get_ts_info. With this change we also have 2 goto and dev_put().

> +
> + dev_put(real_dev);
> + return ret;
> +
> +software:
> info->so_timestamping = SOF_TIMESTAMPING_RX_SOFTWARE |
> SOF_TIMESTAMPING_SOFTWARE;
> info->phc_index = -1;
> -
> return 0;
> }

As Jakub remind, dev_hold() and dev_put() can take NULL now. So how about
this new patch:

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 38e152548126..b5c5196e03ee 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -5591,16 +5591,23 @@ static int bond_ethtool_get_ts_info(struct net_device *bond_dev,
const struct ethtool_ops *ops;
struct net_device *real_dev;
struct phy_device *phydev;
+ int ret = 0;

+ rcu_read_lock();
real_dev = bond_option_active_slave_get_rcu(bond);
+ dev_hold(real_dev);
+ rcu_read_unlock();
+
if (real_dev) {
ops = real_dev->ethtool_ops;
phydev = real_dev->phydev;

if (phy_has_tsinfo(phydev)) {
- return phy_ts_info(phydev, info);
+ ret = phy_ts_info(phydev, info);
+ goto out;
} else if (ops->get_ts_info) {
- return ops->get_ts_info(real_dev, info);
+ ret = ops->get_ts_info(real_dev, info);
+ goto out;
}
}

@@ -5608,7 +5615,9 @@ static int bond_ethtool_get_ts_info(struct net_device *bond_dev,
SOF_TIMESTAMPING_SOFTWARE;
info->phc_index = -1;

- return 0;
+out:
+ dev_put(real_dev);
+ return ret;
}

Thanks
Hangbin

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