These methods generally consume ownership of the provided skb, so even if an error path is encountered, the skb is freed. This is because the very first thing they do after some initial setup is to unconditionally consume the skb via consume_skb(skb). Any subsequent errors lead to the core netlink layer freeing the skb. However, there is one check that occurs before ownership is passed, which is the check for the group index. So if this error condition is encountered, then the skb is leaked. This error condition is generally considered a violation of the netlink API, so it's not expected to occur under normal circumstances. For the same reason, no callers check for this error condition, and no callers need to be adjusted. However, we should still follow the same ownership semantics of the rest of the function. Thus, free the skb in this codepath. Assisted-by: Antigravity:gemini Suggested-by: Andrew Lunn Suggested-by: Matthew Maurer Fixes: 2a94fe48f32c ("genetlink: make multicast groups const, prevent abuse") Link: https://lore.kernel.org/r/845b36ba-7b3a-41f2-acb2-b284f253e2ca@lunn.ch Signed-off-by: Alice Ryhl --- Changes in v2: - Add Fixes: tag. - Specify target branch. - Link to v1: https://lore.kernel.org/r/20260504-genlmsg-return-v1-1-093f3ba970af@google.com --- include/net/genetlink.h | 4 +++- net/netlink/genetlink.c | 8 ++++++-- 2 files changed, 9 insertions(+), 3 deletions(-) diff --git a/include/net/genetlink.h b/include/net/genetlink.h index 7b84f2cef8b1..d70510ac31ab 100644 --- a/include/net/genetlink.h +++ b/include/net/genetlink.h @@ -489,8 +489,10 @@ genlmsg_multicast_netns_filtered(const struct genl_family *family, netlink_filter_fn filter, void *filter_data) { - if (WARN_ON_ONCE(group >= family->n_mcgrps)) + if (WARN_ON_ONCE(group >= family->n_mcgrps)) { + nlmsg_free(skb); return -EINVAL; + } group = family->mcgrp_offset + group; return nlmsg_multicast_filtered(net->genl_sock, skb, portid, group, flags, filter, filter_data); diff --git a/net/netlink/genetlink.c b/net/netlink/genetlink.c index d251d894afd4..0da39eaed255 100644 --- a/net/netlink/genetlink.c +++ b/net/netlink/genetlink.c @@ -1972,8 +1972,10 @@ int genlmsg_multicast_allns(const struct genl_family *family, struct sk_buff *skb, u32 portid, unsigned int group) { - if (WARN_ON_ONCE(group >= family->n_mcgrps)) + if (WARN_ON_ONCE(group >= family->n_mcgrps)) { + kfree_skb(skb); return -EINVAL; + } group = family->mcgrp_offset + group; return genlmsg_mcast(skb, portid, group); @@ -1986,8 +1988,10 @@ void genl_notify(const struct genl_family *family, struct sk_buff *skb, struct net *net = genl_info_net(info); struct sock *sk = net->genl_sock; - if (WARN_ON_ONCE(group >= family->n_mcgrps)) + if (WARN_ON_ONCE(group >= family->n_mcgrps)) { + kfree_skb(skb); return; + } group = family->mcgrp_offset + group; nlmsg_notify(sk, skb, info->snd_portid, group, --- base-commit: 7fd2df204f342fc17d1a0bfcd474b24232fb0f32 change-id: 20260504-genlmsg-return-1e5d6a74d440 Best regards, -- Alice Ryhl