From 3b66b4fcefd7c74477c48b5ccba63f198d41b2aa Mon Sep 17 00:00:00 2001 From: Salvatore Bonaccorso Date: Wed, 7 Dec 2016 10:34:03 +0100 Subject: [PATCH] packet: fix race condition in packet_set_ring (CVE-2016-8655) --- debian/changelog | 1 + ...ix-race-condition-in-packet_set_ring.patch | 92 +++++++++++++++++++ debian/patches/series | 1 + 3 files changed, 94 insertions(+) create mode 100644 debian/patches/bugfix/all/packet-fix-race-condition-in-packet_set_ring.patch diff --git a/debian/changelog b/debian/changelog index 9452a9a50..180b56ff7 100644 --- a/debian/changelog +++ b/debian/changelog @@ -45,6 +45,7 @@ linux (4.8.12-1) UNRELEASED; urgency=medium [ Salvatore Bonaccorso ] * tipc: check minimum bearer MTU (CVE-2016-8632) + * packet: fix race condition in packet_set_ring (CVE-2016-8655) -- Uwe Kleine-König Sun, 04 Dec 2016 21:16:06 +0100 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 000000000..8368add11 --- /dev/null +++ b/debian/patches/bugfix/all/packet-fix-race-condition-in-packet_set_ring.patch @@ -0,0 +1,92 @@ +From: Philip Pettersson +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 + +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 +Signed-off-by: Eric Dumazet +Signed-off-by: David S. Miller +--- + 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 d2238b2..dd23323 100644 +--- a/net/packet/af_packet.c ++++ b/net/packet/af_packet.c +@@ -3648,19 +3648,25 @@ 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: + { +@@ -4164,6 +4170,7 @@ 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)) { + net_warn_ratelimited("Tx-ring is not supported.\n"); +@@ -4245,7 +4252,6 @@ 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); +@@ -4294,11 +4300,11 @@ static int packet_set_ring(struct sock *sk, union tpacket_req_u *req_u, + if (!tx_ring) + prb_shutdown_retire_blk_timer(po, rb_queue); + } +- release_sock(sk); + + if (pg_vec) + free_pg_vec(pg_vec, order, req->tp_block_nr); + out: ++ release_sock(sk); + return err; + } + +-- +2.1.4 + diff --git a/debian/patches/series b/debian/patches/series index a27b8e6f1..fca2ec567 100644 --- a/debian/patches/series +++ b/debian/patches/series @@ -103,6 +103,7 @@ bugfix/all/fs-Avoid-premature-clearing-of-capabilities.patch bugfix/all/vfio-pci-Fix-integer-overflows-bitmask-check.patch bugfix/all/mnt-Add-a-per-mount-namespace-limit-on-the-number-of.patch bugfix/all/tipc-check-minimum-bearer-MTU.patch +bugfix/all/packet-fix-race-condition-in-packet_set_ring.patch # ABI maintenance