4.4-stable review patch. If anyone has any objections, please let me know.
------------------ From: WANG Cong <[email protected]> [ 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: [email protected] Reported-by: Dave Jones <[email protected]> Reported-by: liujian (CE) <[email protected]> Tested-by: liujian (CE) <[email protected]> Cc: Ding Tianhong <[email protected]> Cc: Willem de Bruijn <[email protected]> Signed-off-by: Cong Wang <[email protected]> Signed-off-by: David S. Miller <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- 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);
