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ethtool: rss: avoid modifying the RSS context response

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Gemini says that we're modifying the RSS_CREATE response skb.
I think it's right, the comment says that unicast() should
unshare the skb but I'm not entirely sure what I meant there.
netlink_trim() does a copy but only if skb is not well sized
(it's at least 2x larger than necessary for the payload).

Fixes: a166ab7816 ("ethtool: rss: support creating contexts via Netlink")
Link: https://patch.msgid.link/20260522230647.1705600-2-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Jakub Kicinski 2026-05-22 16:06:42 -07:00
parent 2e357f002c
commit c75b6f6eaa
1 changed files with 10 additions and 8 deletions
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18
net/ethtool/rss.c
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@ -981,11 +981,17 @@ ethnl_rss_create_validate(struct net_device *dev, struct genl_info *info)
}
static void
ethnl_rss_create_send_ntf(struct sk_buff *rsp, struct net_device *dev)
ethnl_rss_create_send_ntf(const struct sk_buff *rsp, struct net_device *dev)
{
struct nlmsghdr *nlh = (void *)rsp->data;
struct genlmsghdr *genl_hdr;
struct nlmsghdr *nlh;
struct sk_buff *ntf;
ntf = skb_copy_expand(rsp, 0, 0, GFP_KERNEL);
if (!ntf)
return;
nlh = nlmsg_hdr(ntf);
/* Convert the reply into a notification */
nlh->nlmsg_pid = 0;
nlh->nlmsg_seq = ethnl_bcast_seq_next();
@ -993,7 +999,7 @@ ethnl_rss_create_send_ntf(struct sk_buff *rsp, struct net_device *dev)
genl_hdr = nlmsg_data(nlh);
genl_hdr->cmd = ETHTOOL_MSG_RSS_CREATE_NTF;
ethnl_multicast(rsp, dev);
ethnl_multicast(ntf, dev);
}
int ethnl_rss_create_doit(struct sk_buff *skb, struct genl_info *info)
@ -1104,12 +1110,8 @@ int ethnl_rss_create_doit(struct sk_buff *skb, struct genl_info *info)
genlmsg_end(rsp, hdr);
/* Use the same skb for the response and the notification,
* genlmsg_reply() will copy the skb if it has elevated user count.
*/
skb_get(rsp);
ret = genlmsg_reply(rsp, info);
ethnl_rss_create_send_ntf(rsp, dev);
ret = genlmsg_reply(rsp, info);
rsp = NULL;
exit_unlock: