[PATCH net 1/2] genetlink: report the real command id for dump-only ops in policy dumps

[Jakub Kicinski <kuba@kernel.org>]

The op-to-policy map a CTRL_CMD_GETPOLICY dump returns is the only way
for userspace to find out which policy index belongs to which command.
ctrl_dumppolicy_put_op() tags the nest with doit->cmd, but an op which
only has a dumpit has no doit and every path which fills the split ops
in zeroes it out, so those entries all claim to be command 0.  nlctrl's
own CTRL_CMD_GETPOLICY and NETDEV_CMD_QSTATS_GET are both in that group:

  [{'family-id': 16, 'op-policy': {'do': 0, 'dump': 0, 'op-id': 3}},
   {'family-id': 16, 'op-policy': {'dump': 1, 'op-id': 0}},

ctrl_fill_info() gets this right - it uses the iterator's cmd for
CTRL_ATTR_OP_ID - so the two introspection interfaces of the same family
contradict each other today.

Pass the command in rather than reconstructing it from
doit->cmd | dumpit->cmd inside the helper, both callers already have it.

Fixes: 26588edbef60 ("genetlink: support split policies in ctrl_dumppolicy_put_op()")
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
 net/netlink/genetlink.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/net/netlink/genetlink.c b/net/netlink/genetlink.c
index 41d37442f186..5cc1037d4917 100644
--- a/net/netlink/genetlink.c
+++ b/net/netlink/genetlink.c
@@ -1656,7 +1656,7 @@ static void *ctrl_dumppolicy_prep(struct sk_buff *skb,
 }
 
 static int ctrl_dumppolicy_put_op(struct sk_buff *skb,
-				  struct netlink_callback *cb,
+				  struct netlink_callback *cb, u32 cmd,
 				  struct genl_split_ops *doit,
 				  struct genl_split_ops *dumpit)
 {
@@ -1677,7 +1677,7 @@ static int ctrl_dumppolicy_put_op(struct sk_buff *skb,
 	if (!nest_pol)
 		goto err;
 
-	nest_op = nla_nest_start(skb, doit->cmd);
+	nest_op = nla_nest_start(skb, cmd);
 	if (!nest_op)
 		goto err;
 
@@ -1721,7 +1721,8 @@ static int ctrl_dumppolicy(struct sk_buff *skb, struct netlink_callback *cb)
 						      &doit, &dumpit)))
 				return -ENOENT;
 
-			if (ctrl_dumppolicy_put_op(skb, cb, &doit, &dumpit))
+			if (ctrl_dumppolicy_put_op(skb, cb, ctx->op,
+						   &doit, &dumpit))
 				return skb->len;
 
 			/* done with the per-op policy index list */
@@ -1730,6 +1731,7 @@ static int ctrl_dumppolicy(struct sk_buff *skb, struct netlink_callback *cb)
 
 		while (ctx->dump_map) {
 			if (ctrl_dumppolicy_put_op(skb, cb,
+						   ctx->op_iter->cmd,
 						   &ctx->op_iter->doit,
 						   &ctx->op_iter->dumpit))
 				return skb->len;
-- 
2.55.0