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bpf, sockmap: Fix update element with same

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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
This commit is contained in:
Michal Luczaj 2024-12-02 12:29:23 +01:00 committed by Daniel Borkmann
parent fac04efc5c
commit 75e072a390
1 changed files with 1 additions and 0 deletions
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net/core/sock_map.c
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@ -159,6 +159,7 @@ static void sock_map_del_link(struct sock *sk,
verdict_stop = true; verdict_stop = true;
list_del(&link->list); list_del(&link->list);
sk_psock_free_link(link); sk_psock_free_link(link);
break;
} }
} }
spin_unlock_bh(&psock->link_lock); spin_unlock_bh(&psock->link_lock);