[linux] 11/18: packet: fix race condition in packet_set_ring (CVE-2016-8655)

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benh pushed a commit to branch jessie
in repository linux.

commit 45b63de79eea5ce0242990877f511d0621b97204
Author: Ben Hutchings <ben at decadent.org.uk>
Date:   Wed Dec 28 23:28:02 2016 +0000

    packet: fix race condition in packet_set_ring (CVE-2016-8655)
---
 debian/changelog                                   |  1 +
 ...ket-fix-race-condition-in-packet_set_ring.patch | 88 ++++++++++++++++++++++
 debian/patches/series                              |  1 +
 3 files changed, 90 insertions(+)

diff --git a/debian/changelog b/debian/changelog
index d6cfb7e..a767f3e 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -501,6 +501,7 @@ linux (3.16.39-1) UNRELEASED; urgency=medium
   * rose,dccp: limit sk_filter trim to payload
   * tcp: take care of truncations done by sk_filter() (CVE-2016-8645)
   * mpi: Fix NULL ptr dereference in mpi_powm() [ver #3] (CVE-2016-8650)
+  * packet: fix race condition in packet_set_ring (CVE-2016-8655)
 
   [ Julien Cristau ]
   * hwrng: Add chaoskey driver, backported from 4.8 (Closes: #839616)
diff --git a/debian/patches/bugfix/all/packet-fix-race-condition-in-packet_set_ring.patch b/debian/patches/bugfix/all/packet-fix-race-condition-in-packet_set_ring.patch
new file mode 100644
index 0000000..775a218
--- /dev/null
+++ b/debian/patches/bugfix/all/packet-fix-race-condition-in-packet_set_ring.patch
@@ -0,0 +1,88 @@
+From: Philip Pettersson <philip.pettersson at gmail.com>
+Date: Wed, 30 Nov 2016 14:55:36 -0800
+Subject: packet: fix race condition in packet_set_ring
+Origin: https://git.kernel.org/linus/84ac7260236a49c79eede91617700174c2c19b0c
+Bug-Debian-Security: https://security-tracker.debian.org/tracker/CVE-2016-8655
+
+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.
+
+Fixes: f6fb8f100b80 ("af-packet: TPACKET_V3 flexible buffer implementation.")
+Signed-off-by: Philip Pettersson <philip.pettersson at gmail.com>
+Signed-off-by: Eric Dumazet <edumazet at google.com>
+Signed-off-by: David S. Miller <davem at davemloft.net>
+---
+ net/packet/af_packet.c | 18 ++++++++++++------
+ 1 file changed, 12 insertions(+), 6 deletions(-)
+
+--- a/net/packet/af_packet.c
++++ b/net/packet/af_packet.c
+@@ -3293,19 +3293,25 @@ packet_setsockopt(struct socket *sock, i
+ 
+ 		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:
+ 	{
+@@ -3768,6 +3774,7 @@ static int packet_set_ring(struct sock *
+ 	/* 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");
+@@ -3849,7 +3856,6 @@ static int packet_set_ring(struct sock *
+ 			goto out;
+ 	}
+ 
+-	lock_sock(sk);
+ 
+ 	/* Detach socket from network */
+ 	spin_lock(&po->bind_lock);
+@@ -3898,11 +3904,11 @@ static int packet_set_ring(struct sock *
+ 		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;
+ }
+ 
diff --git a/debian/patches/series b/debian/patches/series
index 5c1a4b1..815efa6 100644
--- a/debian/patches/series
+++ b/debian/patches/series
@@ -669,6 +669,7 @@ bugfix/all/rose-limit-sk_filter-trim-to-payload.patch
 bugfix/all/dccp-limit-sk_filter-trim-to-payload.patch
 bugfix/all/tcp-take-care-of-truncations-done-by-sk_filter.patch
 bugfix/all/mpi-fix-null-ptr-dereference-in-mpi_powm-ver-3.patch
+bugfix/all/packet-fix-race-condition-in-packet_set_ring.patch
 
 # Fix ABI changes
 debian/of-fix-abi-changes.patch

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