| From foo@baz Tue Aug 8 16:51:58 PDT 2017 |
| From: WANG Cong <xiyou.wangcong@gmail.com> |
| Date: Mon, 24 Jul 2017 10:07:32 -0700 |
| Subject: packet: fix use-after-free in prb_retire_rx_blk_timer_expired() |
| |
| From: WANG Cong <xiyou.wangcong@gmail.com> |
| |
| |
| [ Upstream commit c800aaf8d869f2b9b47b10c5c312fe19f0a94042 ] |
| |
| There are multiple reports showing we have a use-after-free in |
| the timer prb_retire_rx_blk_timer_expired(), where we use struct |
| tpacket_kbdq_core::pkbdq, a pg_vec, after it gets freed by |
| free_pg_vec(). |
| |
| The interesting part is it is not freed via packet_release() but |
| via packet_setsockopt(), which means we are not closing the socket. |
| Looking into the big and fat function packet_set_ring(), this could |
| happen if we satisfy the following conditions: |
| |
| 1. closing == 0, not on packet_release() path |
| 2. req->tp_block_nr == 0, we don't allocate a new pg_vec |
| 3. rx_ring->pg_vec is already set as V3, which means we already called |
| packet_set_ring() wtih req->tp_block_nr > 0 previously |
| 4. req->tp_frame_nr == 0, pass sanity check |
| 5. po->mapped == 0, never called mmap() |
| |
| In this scenario we are clearing the old rx_ring->pg_vec, so we need |
| to free this pg_vec, but we don't stop the timer on this path because |
| of closing==0. |
| |
| The timer has to be stopped as long as we need to free pg_vec, therefore |
| the check on closing!=0 is wrong, we should check pg_vec!=NULL instead. |
| |
| Thanks to liujian for testing different fixes. |
| |
| Reported-by: alexander.levin@verizon.com |
| Reported-by: Dave Jones <davej@codemonkey.org.uk> |
| Reported-by: liujian (CE) <liujian56@huawei.com> |
| Tested-by: liujian (CE) <liujian56@huawei.com> |
| Cc: Ding Tianhong <dingtianhong@huawei.com> |
| Cc: Willem de Bruijn <willemdebruijn.kernel@gmail.com> |
| Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com> |
| Signed-off-by: David S. Miller <davem@davemloft.net> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| --- |
| net/packet/af_packet.c | 2 +- |
| 1 file changed, 1 insertion(+), 1 deletion(-) |
| |
| --- a/net/packet/af_packet.c |
| +++ b/net/packet/af_packet.c |
| @@ -4225,7 +4225,7 @@ static int packet_set_ring(struct sock * |
| register_prot_hook(sk); |
| } |
| spin_unlock(&po->bind_lock); |
| - if (closing && (po->tp_version > TPACKET_V2)) { |
| + if (pg_vec && (po->tp_version > TPACKET_V2)) { |
| /* Because we don't support block-based V3 on tx-ring */ |
| if (!tx_ring) |
| prb_shutdown_retire_blk_timer(po, rb_queue); |