On Thu, 30 Oct 2025 09:36:21 +0000 Jiaming Zhang r772577952@gmail.com wrote:

The ethtool tsconfig Netlink path can trigger a null pointer dereference. A call chain such as:

tsconfig_prepare_data() -> dev_get_hwtstamp_phylib() -> vlan_hwtstamp_get() -> generic_hwtstamp_get_lower() -> generic_hwtstamp_ioctl_lower()

results in generic_hwtstamp_ioctl_lower() being called with kernel_cfg->ifr as NULL.

The generic_hwtstamp_ioctl_lower() function does not expect a NULL ifr and dereferences it, leading to a system crash.

Fix this by adding a NULL check for kernel_cfg->ifr in generic_hwtstamp_get/set_lower(). If ifr is NULL, return -EOPNOTSUPP to prevent the call to the legacy IOCTL helper.

Fixes: 6e9e2eed4f39 ("net: ethtool: Add support for tsconfig command to get/set hwtstamp config") Closes: https://lore.kernel.org/lkml/cd6a7056-fa6d-43f8-b78a-f5e811247ba8@linux.dev/... Signed-off-by: Jiaming Zhang r772577952@gmail.com --- net/core/dev_ioctl.c | 8 ++++++++ 1 file changed, 8 insertions(+)

diff --git a/net/core/dev_ioctl.c b/net/core/dev_ioctl.c index ad54b12d4b4c..39eaf6ba981a 100644 --- a/net/core/dev_ioctl.c +++ b/net/core/dev_ioctl.c @@ -474,6 +474,10 @@ int generic_hwtstamp_get_lower(struct net_device *dev, return err; }

• /* Netlink path with unconverted driver */

nit: "lower driver", to be precise.

With this change: Reviewed-by: Kory Maincent kory.maincent@bootlin.com

Thank you!

• if (!kernel_cfg->ifr)

• return -EOPNOTSUPP;
  

• /* Legacy path: unconverted lower driver */ return generic_hwtstamp_ioctl_lower(dev, SIOCGHWTSTAMP, kernel_cfg);

} @@ -498,6 +502,10 @@ int generic_hwtstamp_set_lower(struct net_device *dev, return err; }

• /* Netlink path with unconverted driver */

same.

• if (!kernel_cfg->ifr)

• return -EOPNOTSUPP;
  

• /* Legacy path: unconverted lower driver */ return generic_hwtstamp_ioctl_lower(dev, SIOCSHWTSTAMP, kernel_cfg);

}