Re: [PATCH net-next v14 12/13] net: ethtool: strset: Allow querying phy stats by index

Hello Simon,

On Tue, 2 Jul 2024 11:54:11 +0100
Simon Horman [off-list ref] wrote:

On Mon, Jul 01, 2024 at 03:17:58PM +0200, Maxime Chevallier wrote:

quoted

The ETH_SS_PHY_STATS command gets PHY statistics. Use the phydev pointer
from the ethnl request to allow query phy stats from each PHY on the
link.

Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
---
 net/ethtool/strset.c | 24 +++++++++++++++++-------
 1 file changed, 17 insertions(+), 7 deletions(-)

diff --git a/net/ethtool/strset.c b/net/ethtool/strset.c  

...

quoted

@@ -279,6 +280,8 @@ static int strset_prepare_data(const struct ethnl_req_info *req_base,
 	const struct strset_req_info *req_info = STRSET_REQINFO(req_base);
 	struct strset_reply_data *data = STRSET_REPDATA(reply_base);
 	struct net_device *dev = reply_base->dev;
+	struct nlattr **tb = info->attrs;  

Hi Maxime,

Elsewhere in this function it is assumed that info may be NULL.
But here it is dereferenced unconditionally.

Hmm in almst all netlink commands we do dereference the genl_info *info
pointer without checks.

I've looked into net/netlink/genetlink.c to backtrack call-sites and it
looks to be that indeed info can't be NULL (either populated from
genl_start() or genl_family_rcv_msg_doit(). Maybe Jakub can confirm
this ?

If what I say above is correct, I can include a small patch to remove
the un-necessary check that makes smatch think the genl_info pointer can
be NULL.

Thanks for the report,

Maxime