From 1158ecd51ec163396d649daedb36440cdaf85443 Mon Sep 17 00:00:00 2001 From: Xin Long Date: Wed, 15 Nov 2017 16:55:54 +0800 Subject: sctp: do not free asoc when it is already dead in sctp_sendmsg [ Upstream commit ca3af4dd28cff4e7216e213ba3b671fbf9f84758 ] Now in sctp_sendmsg sctp_wait_for_sndbuf could schedule out without holding sock sk. It means the current asoc can be freed elsewhere, like when receiving an abort packet. If the asoc is just created in sctp_sendmsg and sctp_wait_for_sndbuf returns err, the asoc will be freed again due to new_asoc is not nil. An use-after-free issue would be triggered by this. This patch is to fix it by setting new_asoc with nil if the asoc is already dead when cpu schedules back, so that it will not be freed again in sctp_sendmsg. v1->v2: set new_asoc as nil in sctp_sendmsg instead of sctp_wait_for_sndbuf. Suggested-by: Neil Horman Reported-by: Dmitry Vyukov Signed-off-by: Xin Long Acked-by: Neil Horman Signed-off-by: David S. Miller Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- net/sctp/socket.c | 17 ++++++++++++++--- 1 file changed, 14 insertions(+), 3 deletions(-) diff --git a/net/sctp/socket.c b/net/sctp/socket.c index c062ceae19e6..121e204d8e4b 100644 --- a/net/sctp/socket.c +++ b/net/sctp/socket.c @@ -1958,8 +1958,14 @@ static int sctp_sendmsg(struct sock *sk, struct msghdr *msg, size_t msg_len) timeo = sock_sndtimeo(sk, msg->msg_flags & MSG_DONTWAIT); if (!sctp_wspace(asoc)) { err = sctp_wait_for_sndbuf(asoc, &timeo, msg_len); - if (err) + if (err) { + if (err == -ESRCH) { + /* asoc is already dead. */ + new_asoc = NULL; + err = -EPIPE; + } goto out_free; + } } /* If an address is passed with the sendto/sendmsg call, it is used @@ -7457,10 +7463,11 @@ static int sctp_wait_for_sndbuf(struct sctp_association *asoc, long *timeo_p, for (;;) { prepare_to_wait_exclusive(&asoc->wait, &wait, TASK_INTERRUPTIBLE); + if (asoc->base.dead) + goto do_dead; if (!*timeo_p) goto do_nonblock; - if (sk->sk_err || asoc->state >= SCTP_STATE_SHUTDOWN_PENDING || - asoc->base.dead) + if (sk->sk_err || asoc->state >= SCTP_STATE_SHUTDOWN_PENDING) goto do_error; if (signal_pending(current)) goto do_interrupted; @@ -7485,6 +7492,10 @@ out: return err; +do_dead: + err = -ESRCH; + goto out; + do_error: err = -EPIPE; goto out; -- cgit v1.2.3