netdev - [PATCH net-next v3 04/13] genetlink: load policy based on validation flags

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Date:   Fri,  4 Nov 2022 12:13:34 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     davem@...emloft.net
Cc:     netdev@...r.kernel.org, edumazet@...gle.com, pabeni@...hat.com,
        jiri@...nulli.us, razor@...ckwall.org, nicolas.dichtel@...nd.com,
        gnault@...hat.com, jacob.e.keller@...el.com, fw@...len.de,
        Jakub Kicinski <kuba@...nel.org>
Subject: [PATCH net-next v3 04/13] genetlink: load policy based on validation flags

Set the policy and maxattr pointers based on validation flags.
genl_family_rcv_msg_attrs_parse() will do nothing and return NULL
if maxattrs is zero, so no behavior change is expected.

Signed-off-by: Jakub Kicinski <kuba@...nel.org>
Reviewed-by: Jacob Keller <jacob.e.keller@...el.com>
---
v2: improve commit msg
---
 net/netlink/genetlink.c | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/net/netlink/genetlink.c b/net/netlink/genetlink.c
index c66299740c05..770726ac491e 100644
--- a/net/netlink/genetlink.c
+++ b/net/netlink/genetlink.c
@@ -204,8 +204,14 @@ genl_cmd_full_to_split(struct genl_split_ops *op,
 		op->post_doit	= family->post_doit;
 	}
 
-	op->policy		= full->policy;
-	op->maxattr		= full->maxattr;
+	if (flags & GENL_CMD_CAP_DUMP &&
+	    full->validate & GENL_DONT_VALIDATE_DUMP) {
+		op->policy	= NULL;
+		op->maxattr	= 0;
+	} else {
+		op->policy	= full->policy;
+		op->maxattr	= full->maxattr;
+	}
 
 	op->cmd			= full->cmd;
 	op->internal_flags	= full->internal_flags;
@@ -638,10 +644,8 @@ static int genl_start(struct netlink_callback *cb)
 	int rc = 0;
 
 	ops = ctx->ops;
-	if (ops->validate & GENL_DONT_VALIDATE_DUMP)
-		goto no_attrs;
-
-	if (ctx->nlh->nlmsg_len < nlmsg_msg_size(ctx->hdrlen))
+	if (!(ops->validate & GENL_DONT_VALIDATE_DUMP) &&
+	    ctx->nlh->nlmsg_len < nlmsg_msg_size(ctx->hdrlen))
 		return -EINVAL;
 
 	attrs = genl_family_rcv_msg_attrs_parse(ctx->family, ctx->nlh, ctx->extack,
@@ -650,7 +654,6 @@ static int genl_start(struct netlink_callback *cb)
 	if (IS_ERR(attrs))
 		return PTR_ERR(attrs);
 
-no_attrs:
 	info = genl_dumpit_info_alloc();
 	if (!info) {
 		genl_family_rcv_msg_attrs_free(attrs);
-- 
2.38.1