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Subject[PATCH 3.12 33/38] packet: fix race condition in packet_set_ring
Date
From: Philip Pettersson <philip.pettersson@gmail.com>

3.12-stable review patch. If anyone has any objections, please let me know.

===============

[ 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.

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: Jiri Slaby <jslaby@suse.cz>
---
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 3f9804b2802a..40d82575adc1 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -3115,19 +3115,25 @@ 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:
{
@@ -3584,6 +3590,7 @@ 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");
@@ -3665,7 +3672,6 @@ 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);
@@ -3714,11 +3720,11 @@ 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;
}

--
2.11.0
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