From 8200f2085abe7f29a016381f3122000cc7b2a760 Mon Sep 17 00:00:00 2001 From: Stephen Hemminger Date: Sat, 4 Mar 2017 18:13:57 -0700 Subject: vmbus: use rcu for per-cpu channel list The per-cpu channel list is now referred to in the interrupt routine. This is mostly safe since the host will not normally generate an interrupt when channel is being deleted but if it did then there would be a use after free problem. To solve, this use RCU protection on ther per-cpu list. Fixes: 631e63a9f346 ("vmbus: change to per channel tasklet") Signed-off-by: Stephen Hemminger Signed-off-by: K. Y. Srinivasan Signed-off-by: Greg Kroah-Hartman --- include/linux/hyperv.h | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'include/linux/hyperv.h') diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h index 62bbf3c1aa4a..c4c7ae91f9d1 100644 --- a/include/linux/hyperv.h +++ b/include/linux/hyperv.h @@ -845,6 +845,13 @@ struct vmbus_channel { * link up channels based on their CPU affinity. */ struct list_head percpu_list; + + /* + * Defer freeing channel until after all cpu's have + * gone through grace period. + */ + struct rcu_head rcu; + /* * For performance critical channels (storage, networking * etc,), Hyper-V has a mechanism to enhance the throughput -- cgit v1.2.3-59-g8ed1b From dad72a1d28442b03aac86836a42de2d00a1014ab Mon Sep 17 00:00:00 2001 From: Dexuan Cui Date: Sat, 4 Mar 2017 18:13:58 -0700 Subject: vmbus: remove hv_event_tasklet_disable/enable With the recent introduction of per-channel tasklet, we need to update the way we handle the 3 concurrency issues: 1. hv_process_channel_removal -> percpu_channel_deq vs. vmbus_chan_sched -> list_for_each_entry(..., percpu_list); 2. vmbus_process_offer -> percpu_channel_enq/deq vs. vmbus_chan_sched. 3. vmbus_close_internal vs. the per-channel tasklet vmbus_on_event; The first 2 issues can be handled by Stephen's recent patch "vmbus: use rcu for per-cpu channel list", and the third issue can be handled by calling tasklet_disable in vmbus_close_internal here. We don't need the original hv_event_tasklet_disable/enable since we now use per-channel tasklet instead of the previous per-CPU tasklet, and actually we must remove them due to the side effect now: vmbus_process_offer -> hv_event_tasklet_enable -> tasklet_schedule will start the per-channel callback prematurely, cauing NULL dereferencing (the channel may haven't been properly configured to run the callback yet). Fixes: 631e63a9f346 ("vmbus: change to per channel tasklet") Signed-off-by: Dexuan Cui Cc: "K. Y. Srinivasan" Cc: Haiyang Zhang Cc: Stephen Hemminger Tested-by: Vitaly Kuznetsov Signed-off-by: K. Y. Srinivasan Signed-off-by: Greg Kroah-Hartman --- drivers/hv/channel.c | 12 ++++-------- drivers/hv/channel_mgmt.c | 19 ------------------- include/linux/hyperv.h | 3 --- 3 files changed, 4 insertions(+), 30 deletions(-) (limited to 'include/linux/hyperv.h') diff --git a/drivers/hv/channel.c b/drivers/hv/channel.c index bd0d1988feb2..57b2958205c7 100644 --- a/drivers/hv/channel.c +++ b/drivers/hv/channel.c @@ -530,15 +530,13 @@ static int vmbus_close_internal(struct vmbus_channel *channel) int ret; /* - * vmbus_on_event(), running in the tasklet, can race + * vmbus_on_event(), running in the per-channel tasklet, can race * with vmbus_close_internal() in the case of SMP guest, e.g., when * the former is accessing channel->inbound.ring_buffer, the latter - * could be freeing the ring_buffer pages. - * - * To resolve the race, we can serialize them by disabling the - * tasklet when the latter is running here. + * could be freeing the ring_buffer pages, so here we must stop it + * first. */ - hv_event_tasklet_disable(channel); + tasklet_disable(&channel->callback_event); /* * In case a device driver's probe() fails (e.g., @@ -605,8 +603,6 @@ static int vmbus_close_internal(struct vmbus_channel *channel) get_order(channel->ringbuffer_pagecount * PAGE_SIZE)); out: - hv_event_tasklet_enable(channel); - return ret; } diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c index d2cfa3eb71a2..bf846d078d85 100644 --- a/drivers/hv/channel_mgmt.c +++ b/drivers/hv/channel_mgmt.c @@ -382,19 +382,6 @@ static void vmbus_release_relid(u32 relid) true); } -void hv_event_tasklet_disable(struct vmbus_channel *channel) -{ - tasklet_disable(&channel->callback_event); -} - -void hv_event_tasklet_enable(struct vmbus_channel *channel) -{ - tasklet_enable(&channel->callback_event); - - /* In case there is any pending event */ - tasklet_schedule(&channel->callback_event); -} - void hv_process_channel_removal(struct vmbus_channel *channel, u32 relid) { unsigned long flags; @@ -403,7 +390,6 @@ void hv_process_channel_removal(struct vmbus_channel *channel, u32 relid) BUG_ON(!channel->rescind); BUG_ON(!mutex_is_locked(&vmbus_connection.channel_mutex)); - hv_event_tasklet_disable(channel); if (channel->target_cpu != get_cpu()) { put_cpu(); smp_call_function_single(channel->target_cpu, @@ -412,7 +398,6 @@ void hv_process_channel_removal(struct vmbus_channel *channel, u32 relid) percpu_channel_deq(channel); put_cpu(); } - hv_event_tasklet_enable(channel); if (channel->primary_channel == NULL) { list_del(&channel->listentry); @@ -506,7 +491,6 @@ static void vmbus_process_offer(struct vmbus_channel *newchannel) init_vp_index(newchannel, dev_type); - hv_event_tasklet_disable(newchannel); if (newchannel->target_cpu != get_cpu()) { put_cpu(); smp_call_function_single(newchannel->target_cpu, @@ -516,7 +500,6 @@ static void vmbus_process_offer(struct vmbus_channel *newchannel) percpu_channel_enq(newchannel); put_cpu(); } - hv_event_tasklet_enable(newchannel); /* * This state is used to indicate a successful open @@ -566,7 +549,6 @@ err_deq_chan: list_del(&newchannel->listentry); mutex_unlock(&vmbus_connection.channel_mutex); - hv_event_tasklet_disable(newchannel); if (newchannel->target_cpu != get_cpu()) { put_cpu(); smp_call_function_single(newchannel->target_cpu, @@ -575,7 +557,6 @@ err_deq_chan: percpu_channel_deq(newchannel); put_cpu(); } - hv_event_tasklet_enable(newchannel); vmbus_release_relid(newchannel->offermsg.child_relid); diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h index c4c7ae91f9d1..970771a5f739 100644 --- a/include/linux/hyperv.h +++ b/include/linux/hyperv.h @@ -1437,9 +1437,6 @@ extern bool vmbus_prep_negotiate_resp(struct icmsg_hdr *icmsghdrp, u8 *buf, const int *srv_version, int srv_vercnt, int *nego_fw_version, int *nego_srv_version); -void hv_event_tasklet_disable(struct vmbus_channel *channel); -void hv_event_tasklet_enable(struct vmbus_channel *channel); - void hv_process_channel_removal(struct vmbus_channel *channel, u32 relid); void vmbus_setevent(struct vmbus_channel *channel); -- cgit v1.2.3-59-g8ed1b