From 67043d756ae5adde318de07ee50e054ba1cf7ea0 Mon Sep 17 00:00:00 2001 From: Philip Pettersson Date: Wed, 7 Dec 2016 08:51:56 +0900 Subject: packet: fix race condition in packet_set_ring 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. Ps. This is CVE-2016-8655 patch, http://seclists.org/oss-sec/2016/q4/607 Change-Id: I3396f1bfe60b03082a981ae9d8a787b41cb5a529 Fixes: f6fb8f100b80 ("af-packet: TPACKET_V3 flexible buffer implementation.") Signed-off-by: Philip Pettersson Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller Signed-off-by: Inki Dae --- 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 a3654d929814..b9d1baaa8bdc 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; } -- cgit v1.2.3