From 1f6ea6e511e5ec730d8e88651da1b7b6e8fd1333 Mon Sep 17 00:00:00 2001 From: David Woodhouse Date: Sat, 7 Aug 2010 23:02:59 -0700 Subject: [PATCH] solos-pci: Fix race condition in tasklet RX handling We were seeing faults in the solos-pci receive tasklet when packets arrived for a VCC which was currently being closed: [18842.727906] EIP: [] br2684_push+0x19/0x234 [br2684] SS:ESP 0068:dfb89d14 [18845.090712] [] ? do_page_fault+0x0/0x2e1 [18845.120042] [] ? br2684_push+0x19/0x234 [br2684] [18845.153530] [] solos_bh+0x28b/0x7c8 [solos_pci] [18845.186488] [] ? solos_irq+0x2d/0x51 [solos_pci] [18845.219960] [] ? handle_irq+0x3b/0x48 [18845.247732] [] ? irq_exit+0x34/0x57 [18845.274437] [] tasklet_action+0x42/0x69 [18845.303247] [] __do_softirq+0x8e/0x129 [18845.331540] [] do_softirq+0x25/0x2a [18845.358274] [] _local_bh_enable_ip+0x5e/0x6a [18845.389677] [] local_bh_enable+0xb/0xe [18845.417944] [] ppp_unregister_channel+0x32/0xbb [ppp_generic] [18845.458193] [] pppox_unbind_sock+0x18/0x1f [pppox] This patch uses an RCU-inspired approach to fix it. In the RX tasklet's find_vcc() function we first refuse to use a VCC which already has the ATM_VF_READY bit cleared. And in the VCC close function, we synchronise with the tasklet to ensure that it can't still be using the VCC before we continue and allow the VCC to be destroyed. Signed-off-by: David Woodhouse Tested-by: Nathan Williams Cc: stable@kernel.org Signed-off-by: David S. Miller --- drivers/atm/solos-pci.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/drivers/atm/solos-pci.c b/drivers/atm/solos-pci.c index 6174965d9a4d..f916ddf63938 100644 --- a/drivers/atm/solos-pci.c +++ b/drivers/atm/solos-pci.c @@ -781,7 +781,8 @@ static struct atm_vcc *find_vcc(struct atm_dev *dev, short vpi, int vci) sk_for_each(s, node, head) { vcc = atm_sk(s); if (vcc->dev == dev && vcc->vci == vci && - vcc->vpi == vpi && vcc->qos.rxtp.traffic_class != ATM_NONE) + vcc->vpi == vpi && vcc->qos.rxtp.traffic_class != ATM_NONE && + test_bit(ATM_VF_READY, &vcc->flags)) goto out; } vcc = NULL; @@ -907,6 +908,10 @@ static void pclose(struct atm_vcc *vcc) clear_bit(ATM_VF_ADDR, &vcc->flags); clear_bit(ATM_VF_READY, &vcc->flags); + /* Hold up vcc_destroy_socket() (our caller) until solos_bh() in the + tasklet has finished processing any incoming packets (and, more to + the point, using the vcc pointer). */ + tasklet_unlock_wait(&card->tlet); return; } -- 2.20.1