Commit 351050ec authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller

kcm: do not attach PF_KCM sockets to avoid deadlock

syzkaller had no problem to trigger a deadlock, attaching a KCM socket
to another one (or itself). (original syzkaller report was a very
confusing lockdep splat during a sendmsg())

It seems KCM claims to only support TCP, but no enforcement is done,
so we might need to add additional checks.

Fixes: ab7ac4eb ("kcm: Kernel Connection Multiplexor module")
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Reported-by: default avatarDmitry Vyukov <dvyukov@google.com>
Acked-by: default avatarTom Herbert <tom@quantonium.net>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent f5c3dd4b
...@@ -1383,6 +1383,10 @@ static int kcm_attach(struct socket *sock, struct socket *csock, ...@@ -1383,6 +1383,10 @@ static int kcm_attach(struct socket *sock, struct socket *csock,
if (!csk) if (!csk)
return -EINVAL; return -EINVAL;
/* We must prevent loops or risk deadlock ! */
if (csk->sk_family == PF_KCM)
return -EOPNOTSUPP;
psock = kmem_cache_zalloc(kcm_psockp, GFP_KERNEL); psock = kmem_cache_zalloc(kcm_psockp, GFP_KERNEL);
if (!psock) if (!psock)
return -ENOMEM; return -ENOMEM;
......
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