linux-cavium: CVE-2017-6353

Possible double free in stcp_sendmsg() (incorrect fix for CVE-2017-5986)

Reference:
https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2017-6353

Signed-off-by: Sona Sarmadi <sona.sarmadi@enea.com>
Signed-off-by: Martin Borg <martin.borg@enea.com>

2 files changed, 74 insertions, 0 deletions

diff --git a/recipes-kernel/linux/linux-cavium/CVE-2017-6353.patch b/recipes-kernel/linux/linux-cavium/CVE-2017-6353.patch
new file mode 100644
index 0000000..3ff4dc7
--- /dev/null
+++ b/recipes-kernel/linux/linux-cavium/CVE-2017-6353.patch
@@ -0,0 +1,73 @@
+From 35b9d61ea910c1ebd4652b32cc7d713f6689b4f4 Mon Sep 17 00:00:00 2001
+From: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
+Date: Thu, 23 Feb 2017 09:31:18 -0300
+Subject: [PATCH] sctp: deny peeloff operation on asocs with threads sleeping
+ on it
+
+commit dfcb9f4f99f1e9a49e43398a7bfbf56927544af1 upstream.
+
+commit 2dcab5984841 ("sctp: avoid BUG_ON on sctp_wait_for_sndbuf")
+attempted to avoid a BUG_ON call when the association being used for a
+sendmsg() is blocked waiting for more sndbuf and another thread did a
+peeloff operation on such asoc, moving it to another socket.
+
+As Ben Hutchings noticed, then in such case it would return without
+locking back the socket and would cause two unlocks in a row.
+
+Further analysis also revealed that it could allow a double free if the
+application managed to peeloff the asoc that is created during the
+sendmsg call, because then sctp_sendmsg() would try to free the asoc
+that was created only for that call.
+
+This patch takes another approach. It will deny the peeloff operation
+if there is a thread sleeping on the asoc, so this situation doesn't
+exist anymore. This avoids the issues described above and also honors
+the syscalls that are already being handled (it can be multiple sendmsg
+calls).
+
+Joint work with Xin Long.
+
+CVE: CVE-2017-6353
+Upstream-Status: Backport [from kernel.org longterm 4.9.52]
+
+Fixes: 2dcab5984841 ("sctp: avoid BUG_ON on sctp_wait_for_sndbuf")
+Cc: Alexander Popov <alex.popov@linux.com>
+Cc: Ben Hutchings <ben@decadent.org.uk>
+Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
+Signed-off-by: Xin Long <lucien.xin@gmail.com>
+Signed-off-by: David S. Miller <davem@davemloft.net>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+Signed-off-by: Sona Sarmadi <sona.sarmadi@enea.com>
+---
+ net/sctp/socket.c | 8 ++++++--
+ 1 file changed, 6 insertions(+), 2 deletions(-)
+
+diff --git a/net/sctp/socket.c b/net/sctp/socket.c
+index 6cbe5bd..6734420 100644
+--- a/net/sctp/socket.c
++++ b/net/sctp/socket.c
+@@ -4735,6 +4735,12 @@ int sctp_do_peeloff(struct sock *sk, sctp_assoc_t id, struct socket **sockp)
+        if (!asoc)
+                return -EINVAL;
+ 
++       /* If there is a thread waiting on more sndbuf space for
++        * sending on this asoc, it cannot be peeled.
++        */
++       if (waitqueue_active(&asoc->wait))
++               return -EBUSY;
++
+        /* An association cannot be branched off from an already peeled-off
+         * socket, nor is this supported for tcp style sockets.
+         */
+@@ -7427,8 +7433,6 @@ static int sctp_wait_for_sndbuf(struct sctp_association *asoc, long *timeo_p,
+                 */
+                release_sock(sk);
+                current_timeo = schedule_timeout(current_timeo);
+-               if (sk != asoc->base.sk)
+-                       goto do_error;
+                lock_sock(sk);
+ 
+                *timeo_p = current_timeo;
+-- 
+1.9.1
+
diff --git a/recipes-kernel/linux/linux-cavium_4.9.inc b/recipes-kernel/linux/linux-cavium_4.9.inc
index 13a4bda..39ba2e7 100644
--- a/recipes-kernel/linux/linux-cavium_4.9.inc
+++ b/recipes-kernel/linux/linux-cavium_4.9.inc
@@ -25,6 +25,7 @@ SRC_URI = "git://git@git.enea.com/linux/linux-cavium.git;protocol=ssh;name=machi
            file://CVE-2017-6214.patch \
            file://CVE-2017-6345.patch \
            file://CVE-2017-6348.patch \
+           file://CVE-2017-6353.patch \
            file://CVE-2017-7487.patch \
            file://CVE-2017-7618.patch \
            file://CVE-2017-7645.patch \