| From | Greg Kroah-Hartman <> | Subject | [PATCH 4.12 21/52] kcm: do not attach PF_KCM sockets to avoid deadlock | Date | Mon, 18 Sep 2017 11:11:15 +0200 |
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4.12-stable review patch. If anyone has any objections, please let me know.
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From: Eric Dumazet <edumazet@google.com>
[ Upstream commit 351050ecd6523374b370341cc29fe61e2201556b ]
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: ab7ac4eb9832 ("kcm: Kernel Connection Multiplexor module") Signed-off-by: Eric Dumazet <edumazet@google.com> Reported-by: Dmitry Vyukov <dvyukov@google.com> Acked-by: Tom Herbert <tom@quantonium.net> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> --- net/kcm/kcmsock.c | 4 ++++ 1 file changed, 4 insertions(+)
--- a/net/kcm/kcmsock.c +++ b/net/kcm/kcmsock.c @@ -1383,6 +1383,10 @@ static int kcm_attach(struct socket *soc if (!csk) 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); if (!psock) return -ENOMEM;
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