From 08e8331654d1d7b2c58045e549005bc356aa7810 Mon Sep 17 00:00:00 2001 From: Sabrina Dubroca Date: Thu, 26 Feb 2015 05:35:41 +0000 Subject: [PATCH] e1000: add dummy allocator to fix race condition between mtu change and netpoll There is a race condition between e1000_change_mtu's cleanups and netpoll, when we change the MTU across jumbo size: Changing MTU frees all the rx buffers: e1000_change_mtu -> e1000_down -> e1000_clean_all_rx_rings -> e1000_clean_rx_ring Then, close to the end of e1000_change_mtu: pr_info -> ... -> netpoll_poll_dev -> e1000_clean -> e1000_clean_rx_irq -> e1000_alloc_rx_buffers -> e1000_alloc_frag And when we come back to do the rest of the MTU change: e1000_up -> e1000_configure -> e1000_configure_rx -> e1000_alloc_jumbo_rx_buffers alloc_jumbo finds the buffers already != NULL, since data (shared with page in e1000_rx_buffer->rxbuf) has been re-alloc'd, but it's garbage, or at least not what is expected when in jumbo state. This results in an unusable adapter (packets don't get through), and a NULL pointer dereference on the next call to e1000_clean_rx_ring (other mtu change, link down, shutdown): BUG: unable to handle kernel NULL pointer dereference at (null) IP: [] put_compound_page+0x7e/0x330 [...] Call Trace: [] put_page+0x55/0x60 [] e1000_clean_rx_ring+0x134/0x200 [] e1000_clean_all_rx_rings+0x45/0x60 [] e1000_down+0x1c0/0x1d0 [] ? deactivate_slab+0x7f0/0x840 [] e1000_change_mtu+0xdc/0x170 [] dev_set_mtu+0xa0/0x140 [] do_setlink+0x218/0xac0 [] ? nla_parse+0xb9/0x120 [] rtnl_newlink+0x6d0/0x890 [] ? kvm_clock_read+0x20/0x40 [] ? sched_clock_cpu+0xa8/0x100 [] rtnetlink_rcv_msg+0x92/0x260 By setting the allocator to a dummy version, netpoll can't mess up our rx buffers. The allocator is set back to a sane value in e1000_configure_rx. Fixes: edbbb3ca1077 ("e1000: implement jumbo receive with partial descriptors") Signed-off-by: Sabrina Dubroca Tested-by: Aaron Brown Signed-off-by: Jeff Kirsher --- drivers/net/ethernet/intel/e1000/e1000_main.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/drivers/net/ethernet/intel/e1000/e1000_main.c b/drivers/net/ethernet/intel/e1000/e1000_main.c index 26dcb44ea0c8..73c98d34fa1f 100644 --- a/drivers/net/ethernet/intel/e1000/e1000_main.c +++ b/drivers/net/ethernet/intel/e1000/e1000_main.c @@ -144,6 +144,11 @@ static bool e1000_clean_rx_irq(struct e1000_adapter *adapter, static bool e1000_clean_jumbo_rx_irq(struct e1000_adapter *adapter, struct e1000_rx_ring *rx_ring, int *work_done, int work_to_do); +static void e1000_alloc_dummy_rx_buffers(struct e1000_adapter *adapter, + struct e1000_rx_ring *rx_ring, + int cleaned_count) +{ +} static void e1000_alloc_rx_buffers(struct e1000_adapter *adapter, struct e1000_rx_ring *rx_ring, int cleaned_count); @@ -3552,8 +3557,11 @@ static int e1000_change_mtu(struct net_device *netdev, int new_mtu) msleep(1); /* e1000_down has a dependency on max_frame_size */ hw->max_frame_size = max_frame; - if (netif_running(netdev)) + if (netif_running(netdev)) { + /* prevent buffers from being reallocated */ + adapter->alloc_rx_buf = e1000_alloc_dummy_rx_buffers; e1000_down(adapter); + } /* NOTE: netdev_alloc_skb reserves 16 bytes, and typically NET_IP_ALIGN * means we reserve 2 more, this pushes us to allocate from the next -- 2.20.1