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66 lines
2.4 KiB
Diff
66 lines
2.4 KiB
Diff
From dfcb9f4f99f1e9a49e43398a7bfbf56927544af1 Mon Sep 17 00:00:00 2001
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From: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
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Date: Thu, 23 Feb 2017 09:31:18 -0300
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Subject: sctp: deny peeloff operation on asocs with threads sleeping on it
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commit 2dcab5984841 ("sctp: avoid BUG_ON on sctp_wait_for_sndbuf")
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attempted to avoid a BUG_ON call when the association being used for a
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sendmsg() is blocked waiting for more sndbuf and another thread did a
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peeloff operation on such asoc, moving it to another socket.
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As Ben Hutchings noticed, then in such case it would return without
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locking back the socket and would cause two unlocks in a row.
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Further analysis also revealed that it could allow a double free if the
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application managed to peeloff the asoc that is created during the
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sendmsg call, because then sctp_sendmsg() would try to free the asoc
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that was created only for that call.
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This patch takes another approach. It will deny the peeloff operation
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if there is a thread sleeping on the asoc, so this situation doesn't
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exist anymore. This avoids the issues described above and also honors
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the syscalls that are already being handled (it can be multiple sendmsg
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calls).
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Joint work with Xin Long.
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Fixes: 2dcab5984841 ("sctp: avoid BUG_ON on sctp_wait_for_sndbuf")
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Cc: Alexander Popov <alex.popov@linux.com>
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Cc: Ben Hutchings <ben@decadent.org.uk>
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Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
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Signed-off-by: Xin Long <lucien.xin@gmail.com>
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Signed-off-by: David S. Miller <davem@davemloft.net>
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---
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net/sctp/socket.c | 8 ++++++--
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1 file changed, 6 insertions(+), 2 deletions(-)
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diff --git a/net/sctp/socket.c b/net/sctp/socket.c
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index b532148..465a9c8 100644
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--- a/net/sctp/socket.c
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+++ b/net/sctp/socket.c
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@@ -4862,6 +4862,12 @@ int sctp_do_peeloff(struct sock *sk, sctp_assoc_t id, struct socket **sockp)
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if (!asoc)
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return -EINVAL;
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+ /* If there is a thread waiting on more sndbuf space for
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+ * sending on this asoc, it cannot be peeled.
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+ */
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+ if (waitqueue_active(&asoc->wait))
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+ return -EBUSY;
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+
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/* An association cannot be branched off from an already peeled-off
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* socket, nor is this supported for tcp style sockets.
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*/
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@@ -7599,8 +7605,6 @@ static int sctp_wait_for_sndbuf(struct sctp_association *asoc, long *timeo_p,
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*/
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release_sock(sk);
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current_timeo = schedule_timeout(current_timeo);
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- if (sk != asoc->base.sk)
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- goto do_error;
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lock_sock(sk);
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*timeo_p = current_timeo;
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--
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cgit v1.1
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