From 638fea33aee858cc665297a76f0039e95a28ce0c Mon Sep 17 00:00:00 2001 From: Dexuan Cui Date: Thu, 9 Jun 2016 18:47:24 -0700 Subject: [PATCH] Drivers: hv: vmbus: fix the race when querying & updating the percpu list There is a rare race when we remove an entry from the global list hv_context.percpu_list[cpu] in hv_process_channel_removal() -> percpu_channel_deq() -> list_del(): at this time, if vmbus_on_event() -> process_chn_event() -> pcpu_relid2channel() is trying to query the list, we can get the kernel fault. Similarly, we also have the issue in the code path: vmbus_process_offer() -> percpu_channel_enq(). We can resolve the issue by disabling the tasklet when updating the list. The patch also moves vmbus_release_relid() to a later place where the channel has been removed from the per-cpu and the global lists. Reported-by: Rolf Neugebauer Signed-off-by: Dexuan Cui Signed-off-by: K. Y. Srinivasan Signed-off-by: Greg Kroah-Hartman --- drivers/hv/channel.c | 6 ++---- drivers/hv/channel_mgmt.c | 32 ++++++++++++++++++++++++++++---- include/linux/hyperv.h | 3 +++ 3 files changed, 33 insertions(+), 8 deletions(-) diff --git a/drivers/hv/channel.c b/drivers/hv/channel.c index 9a88c63..e47d37d 100644 --- a/drivers/hv/channel.c +++ b/drivers/hv/channel.c @@ -505,7 +505,6 @@ static void reset_channel_cb(void *arg) static int vmbus_close_internal(struct vmbus_channel *channel) { struct vmbus_channel_close_channel *msg; - struct tasklet_struct *tasklet; int ret; /* @@ -517,8 +516,7 @@ static int vmbus_close_internal(struct vmbus_channel *channel) * To resolve the race, we can serialize them by disabling the * tasklet when the latter is running here. */ - tasklet = hv_context.event_dpc[channel->target_cpu]; - tasklet_disable(tasklet); + hv_event_tasklet_disable(channel); /* * In case a device driver's probe() fails (e.g., @@ -584,7 +582,7 @@ static int vmbus_close_internal(struct vmbus_channel *channel) get_order(channel->ringbuffer_pagecount * PAGE_SIZE)); out: - tasklet_enable(tasklet); + hv_event_tasklet_enable(channel); return ret; } diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c index b6c1211..8818b92 100644 --- a/drivers/hv/channel_mgmt.c +++ b/drivers/hv/channel_mgmt.c @@ -21,6 +21,7 @@ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt #include +#include #include #include #include @@ -303,16 +304,32 @@ static void vmbus_release_relid(u32 relid) vmbus_post_msg(&msg, sizeof(struct vmbus_channel_relid_released)); } +void hv_event_tasklet_disable(struct vmbus_channel *channel) +{ + struct tasklet_struct *tasklet; + tasklet = hv_context.event_dpc[channel->target_cpu]; + tasklet_disable(tasklet); +} + +void hv_event_tasklet_enable(struct vmbus_channel *channel) +{ + struct tasklet_struct *tasklet; + tasklet = hv_context.event_dpc[channel->target_cpu]; + tasklet_enable(tasklet); + + /* In case there is any pending event */ + tasklet_schedule(tasklet); +} + void hv_process_channel_removal(struct vmbus_channel *channel, u32 relid) { unsigned long flags; struct vmbus_channel *primary_channel; - vmbus_release_relid(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, @@ -321,6 +338,7 @@ 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); @@ -341,6 +359,8 @@ void hv_process_channel_removal(struct vmbus_channel *channel, u32 relid) cpumask_clear_cpu(channel->target_cpu, &primary_channel->alloced_cpus_in_node); + vmbus_release_relid(relid); + free_channel(channel); } @@ -409,6 +429,7 @@ 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, @@ -418,6 +439,7 @@ 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 @@ -463,12 +485,11 @@ static void vmbus_process_offer(struct vmbus_channel *newchannel) return; err_deq_chan: - vmbus_release_relid(newchannel->offermsg.child_relid); - mutex_lock(&vmbus_connection.channel_mutex); 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, @@ -477,6 +498,9 @@ err_deq_chan: percpu_channel_deq(newchannel); put_cpu(); } + hv_event_tasklet_enable(newchannel); + + vmbus_release_relid(newchannel->offermsg.child_relid); err_free_chan: free_channel(newchannel); diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h index b10954a..50f493e 100644 --- a/include/linux/hyperv.h +++ b/include/linux/hyperv.h @@ -1357,6 +1357,9 @@ extern bool vmbus_prep_negotiate_resp(struct icmsg_hdr *, struct icmsg_negotiate *, u8 *, int, int); +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); /* -- 2.7.4