packet: CVE-2016-8665

packet: fix race condition in packet_set_ring

References:
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=linux-4.1.y&id=e29fdf045048addaea61c837b60e3c4d2ec43614

Change-Id: I3a9abfa653c6a2d3fede70c8c7f4f7f8df7b3063
Signed-off-by: Andreas Wellving <andreas.wellving@enea.com>

2 files changed, 100 insertions, 0 deletions

diff --git a/patches/cve/4.1.x.scc b/patches/cve/4.1.x.scc
index 26b7fd8..4451d85 100644
--- a/patches/cve/4.1.x.scc
+++ b/patches/cve/4.1.x.scc
@@ -1,3 +1,4 @@
 #fixed in 4.1.37
 patch CVE-2016-7039-net-add-recursion-limit-to-GRO.patch
 patch CVE-2016-8399-net-ping-check-minimum-size-on-ICMP-header-length.patch
+patch CVE-2016-8655-packet-fix-race-condition-in-packet_set_ring.patch
diff --git a/patches/cve/CVE-2016-8655-packet-fix-race-condition-in-packet_set_ring.patch b/patches/cve/CVE-2016-8655-packet-fix-race-condition-in-packet_set_ring.patch
new file mode 100644
index 0000000..edaecc6
--- /dev/null
+++ b/patches/cve/CVE-2016-8655-packet-fix-race-condition-in-packet_set_ring.patch
@@ -0,0 +1,99 @@
+From e29fdf045048addaea61c837b60e3c4d2ec43614 Mon Sep 17 00:00:00 2001
+From: Philip Pettersson <philip.pettersson@gmail.com>
+Date: Wed, 14 Dec 2016 13:24:56 +0100
+Subject: [PATCH] packet: fix race condition in packet_set_ring
+
+[ Upstream commit 84ac7260236a49c79eede91617700174c2c19b0c ]
+
+When packet_set_ring creates a ring buffer it will initialize a
+struct timer_list if the packet version is TPACKET_V3. This value
+can then be raced by a different thread calling setsockopt to
+set the version to TPACKET_V1 before packet_set_ring has finished.
+
+This leads to a use-after-free on a function pointer in the
+struct timer_list when the socket is closed as the previously
+initialized timer will not be deleted.
+
+The bug is fixed by taking lock_sock(sk) in packet_setsockopt when
+changing the packet version while also taking the lock at the start
+of packet_set_ring.
+
+Upstream-Status: Backport  
+References: CVE-2016-8655
+Fixes: f6fb8f100b80 ("af-packet: TPACKET_V3 flexible buffer implementation.")
+Signed-off-by: Philip Pettersson <philip.pettersson@gmail.com>
+Signed-off-by: Eric Dumazet <edumazet@google.com>
+Signed-off-by: David S. Miller <davem@davemloft.net>
+Signed-off-by: Philipp Hahn <hahn@univention.de>
+Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
+Signed-off-by: Andreas Wellving <andreas.wellving@enea.com>
+---
+ net/packet/af_packet.c | 18 ++++++++++++------
+ 1 file changed, 12 insertions(+), 6 deletions(-)
+
+diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
+index a3654d9..b9d1baa 100644
+--- a/net/packet/af_packet.c
++++ b/net/packet/af_packet.c
+@@ -3344,19 +3344,25 @@ packet_setsockopt(struct socket *sock, int level, int optname, char __user *optv
+ 
+                if (optlen != sizeof(val))
+                        return -EINVAL;
+-               if (po->rx_ring.pg_vec || po->tx_ring.pg_vec)
+-                       return -EBUSY;
+                if (copy_from_user(&val, optval, sizeof(val)))
+                        return -EFAULT;
+                switch (val) {
+                case TPACKET_V1:
+                case TPACKET_V2:
+                case TPACKET_V3:
+-                       po->tp_version = val;
+-                       return 0;
++                       break;
+                default:
+                        return -EINVAL;
+                }
++               lock_sock(sk);
++               if (po->rx_ring.pg_vec || po->tx_ring.pg_vec) {
++                       ret = -EBUSY;
++               } else {
++                       po->tp_version = val;
++                       ret = 0;
++               }
++               release_sock(sk);
++               return ret;
+        }
+        case PACKET_RESERVE:
+        {
+@@ -3819,6 +3825,7 @@ static int packet_set_ring(struct sock *sk, union tpacket_req_u *req_u,
+        /* Added to avoid minimal code churn */
+        struct tpacket_req *req = &req_u->req;
+ 
++       lock_sock(sk);
+        /* Opening a Tx-ring is NOT supported in TPACKET_V3 */
+        if (!closing && tx_ring && (po->tp_version > TPACKET_V2)) {
+                WARN(1, "Tx-ring is not supported.\n");
+@@ -3900,7 +3907,6 @@ static int packet_set_ring(struct sock *sk, union tpacket_req_u *req_u,
+                        goto out;
+        }
+ 
+-       lock_sock(sk);
+ 
+        /* Detach socket from network */
+        spin_lock(&po->bind_lock);
+@@ -3949,11 +3955,11 @@ static int packet_set_ring(struct sock *sk, union tpacket_req_u *req_u,
+                if (!tx_ring)
+                        prb_shutdown_retire_blk_timer(po, tx_ring, rb_queue);
+        }
+-       release_sock(sk);
+ 
+        if (pg_vec)
+                free_pg_vec(pg_vec, order, req->tp_block_nr);
+ out:
++       release_sock(sk);
+        return err;
+ }
+ 
+-- 
+2.7.4
+