From: Michal Luczaj <mhal@rbox.co>
Date: Mon, 2 Dec 2024 11:29:23 +0000 (+0100)
Subject: bpf, sockmap: Fix update element with same
X-Git-Tag: v6.13-rc3~9^2~12
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=75e072a390da9a22e7ae4a4e8434dfca5da499fb;p=thirdparty%2Fkernel%2Flinux.git

bpf, sockmap: Fix update element with same

Consider a sockmap entry being updated with the same socket:

	osk = stab->sks[idx];
	sock_map_add_link(psock, link, map, &stab->sks[idx]);
	stab->sks[idx] = sk;
	if (osk)
		sock_map_unref(osk, &stab->sks[idx]);

Due to sock_map_unref(), which invokes sock_map_del_link(), all the
psock's links for stab->sks[idx] are torn:

	list_for_each_entry_safe(link, tmp, &psock->link, list) {
		if (link->link_raw == link_raw) {
			...
			list_del(&link->list);
			sk_psock_free_link(link);
		}
	}

And that includes the new link sock_map_add_link() added just before
the unref.

This results in a sockmap holding a socket, but without the respective
link. This in turn means that close(sock) won't trigger the cleanup,
i.e. a closed socket will not be automatically removed from the sockmap.

Stop tearing the links when a matching link_raw is found.

Fixes: 604326b41a6f ("bpf, sockmap: convert to generic sk_msg interface")
Signed-off-by: Michal Luczaj <mhal@rbox.co>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20241202-sockmap-replace-v1-1-1e88579e7bd5@rbox.co
---

diff --git a/net/core/sock_map.c b/net/core/sock_map.c
index 78347d7d25ef3..20b348b1964a1 100644
--- a/net/core/sock_map.c
+++ b/net/core/sock_map.c
@@ -159,6 +159,7 @@ static void sock_map_del_link(struct sock *sk,
 				verdict_stop = true;
 			list_del(&link->list);
 			sk_psock_free_link(link);
+			break;
 		}
 	}
 	spin_unlock_bh(&psock->link_lock);