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authorEric Dumazet <edumazet@google.com>2017-08-30 09:29:31 -0700
committerDavid S. Miller <davem@davemloft.net>2017-08-30 15:55:10 -0700
commit351050ecd6523374b370341cc29fe61e2201556b (patch)
tree5b6c0a72dcf7b3d172c2be867e5bf2fd10030099
parentf5c3dd4b5363af997d418174d578a795081aab51 (diff)
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: 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>
-rw-r--r--net/kcm/kcmsock.c4
1 files changed, 4 insertions, 0 deletions
diff --git a/net/kcm/kcmsock.c b/net/kcm/kcmsock.c
index da49191f7ad0..4abf6287d7e1 100644
--- a/net/kcm/kcmsock.c
+++ b/net/kcm/kcmsock.c
@@ -1383,6 +1383,10 @@ static int kcm_attach(struct socket *sock, struct socket *csock,
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;