[PATCH net-next v2] net/ethtool/tunnels: check the return value of nla_nest_start()

[PATCH net-next v2] net/ethtool/tunnels: check the return value of nla_nest_start()

[Li Zhong]

Check the return value of nla_nest_start(). When starting the entry
level nested attributes, if the tailroom of socket buffer is
insufficient to store the attribute header and payload, the return value
will be NULL and we should check it. If it is NULL, go to the
error_cancel_entry label to do error handling.

v2: error handling jump to error_cancel_entry, more details in commit 
meesage

Signed-off-by: Li Zhong <floridsleeves@gmail.com>
---
 net/ethtool/tunnels.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/ethtool/tunnels.c b/net/ethtool/tunnels.c
index efde33536687..67fb414ca859 100644
--- a/net/ethtool/tunnels.c
+++ b/net/ethtool/tunnels.c
@@ -136,6 +136,8 @@ ethnl_tunnel_info_fill_reply(const struct ethnl_req_info *req_base,
 			goto err_cancel_table;
 
 		entry = nla_nest_start(skb, ETHTOOL_A_TUNNEL_UDP_TABLE_ENTRY);
+		if (!entry)
+			goto err_cancel_entry;
 
 		if (nla_put_be16(skb, ETHTOOL_A_TUNNEL_UDP_ENTRY_PORT,
 				 htons(IANA_VXLAN_UDP_PORT)) ||
-- 
2.25.1

Re: [PATCH net-next v2] net/ethtool/tunnels: check the return value of nla_nest_start()

[Jakub Kicinski]

On Wed, 21 Sep 2022 01:30:04 -0700 Li Zhong wrote:
> Subject: [PATCH net-next v2] net/ethtool/tunnels: check the return value of nla_nest_start()

Please update the subject to follow the standard kernel convention.
The prefix should be something like

  ethtool: tunnels:

or just

  ethtool:

> Check the return value of nla_nest_start(). When starting the entry
> level nested attributes, if the tailroom of socket buffer is
> insufficient to store the attribute header and payload, the return value
> will be NULL and we should check it. If it is NULL, go to the
> error_cancel_entry label to do error handling.

Better but don't explain what the patch does but lean more into the
assessment of the situation. The last sentence is unnecessary, but
you should include an explanation if there is any _actual_ bug here.
Can something crash or misbehave?

> v2: error handling jump to error_cancel_entry, more details in commit 
> meesage

This should go under the --- separator