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author | Dexuan Cui <decui@microsoft.com> | 2018-11-26 00:26:17 +0000 |
---|---|---|
committer | Martin K. Petersen <martin.petersen@oracle.com> | 2018-11-28 21:33:16 -0500 |
commit | c967590457cae5ba4f018704c341641bdcecfdcf (patch) | |
tree | 90f477ef9ff0072ac65b9a13b2970354053d1a31 /drivers/scsi | |
parent | 02f425f811cefcc4d325d7a72272651e622dc97e (diff) | |
download | linux-stable-c967590457cae5ba4f018704c341641bdcecfdcf.tar.gz linux-stable-c967590457cae5ba4f018704c341641bdcecfdcf.tar.bz2 linux-stable-c967590457cae5ba4f018704c341641bdcecfdcf.zip |
scsi: storvsc: Fix a race in sub-channel creation that can cause panic
We can concurrently try to open the same sub-channel from 2 paths:
path #1: vmbus_onoffer() -> vmbus_process_offer() -> handle_sc_creation().
path #2: storvsc_probe() -> storvsc_connect_to_vsp() ->
-> storvsc_channel_init() -> handle_multichannel_storage() ->
-> vmbus_are_subchannels_present() -> handle_sc_creation().
They conflict with each other, but it was not an issue before the recent
commit ae6935ed7d42 ("vmbus: split ring buffer allocation from open"),
because at the beginning of vmbus_open() we checked newchannel->state so
only one path could succeed, and the other would return with -EINVAL.
After ae6935ed7d42, the failing path frees the channel's ringbuffer by
vmbus_free_ring(), and this causes a panic later.
Commit ae6935ed7d42 itself is good, and it just reveals the longstanding
race. We can resolve the issue by removing path #2, i.e. removing the
second vmbus_are_subchannels_present() in handle_multichannel_storage().
BTW, the comment "Check to see if sub-channels have already been created"
in handle_multichannel_storage() is incorrect: when we unload the driver,
we first close the sub-channel(s) and then close the primary channel, next
the host sends rescind-offer message(s) so primary->sc_list will become
empty. This means the first vmbus_are_subchannels_present() in
handle_multichannel_storage() is never useful.
Fixes: ae6935ed7d42 ("vmbus: split ring buffer allocation from open")
Cc: stable@vger.kernel.org
Cc: Long Li <longli@microsoft.com>
Cc: Stephen Hemminger <sthemmin@microsoft.com>
Cc: K. Y. Srinivasan <kys@microsoft.com>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: Dexuan Cui <decui@microsoft.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Diffstat (limited to 'drivers/scsi')
-rw-r--r-- | drivers/scsi/storvsc_drv.c | 61 |
1 files changed, 30 insertions, 31 deletions
diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c index f03dc03a42c3..8f88348ebe42 100644 --- a/drivers/scsi/storvsc_drv.c +++ b/drivers/scsi/storvsc_drv.c @@ -446,7 +446,6 @@ struct storvsc_device { bool destroy; bool drain_notify; - bool open_sub_channel; atomic_t num_outstanding_req; struct Scsi_Host *host; @@ -636,33 +635,38 @@ get_in_err: static void handle_sc_creation(struct vmbus_channel *new_sc) { struct hv_device *device = new_sc->primary_channel->device_obj; + struct device *dev = &device->device; struct storvsc_device *stor_device; struct vmstorage_channel_properties props; + int ret; stor_device = get_out_stor_device(device); if (!stor_device) return; - if (stor_device->open_sub_channel == false) - return; - memset(&props, 0, sizeof(struct vmstorage_channel_properties)); - vmbus_open(new_sc, - storvsc_ringbuffer_size, - storvsc_ringbuffer_size, - (void *)&props, - sizeof(struct vmstorage_channel_properties), - storvsc_on_channel_callback, new_sc); + ret = vmbus_open(new_sc, + storvsc_ringbuffer_size, + storvsc_ringbuffer_size, + (void *)&props, + sizeof(struct vmstorage_channel_properties), + storvsc_on_channel_callback, new_sc); - if (new_sc->state == CHANNEL_OPENED_STATE) { - stor_device->stor_chns[new_sc->target_cpu] = new_sc; - cpumask_set_cpu(new_sc->target_cpu, &stor_device->alloced_cpus); + /* In case vmbus_open() fails, we don't use the sub-channel. */ + if (ret != 0) { + dev_err(dev, "Failed to open sub-channel: err=%d\n", ret); + return; } + + /* Add the sub-channel to the array of available channels. */ + stor_device->stor_chns[new_sc->target_cpu] = new_sc; + cpumask_set_cpu(new_sc->target_cpu, &stor_device->alloced_cpus); } static void handle_multichannel_storage(struct hv_device *device, int max_chns) { + struct device *dev = &device->device; struct storvsc_device *stor_device; int num_cpus = num_online_cpus(); int num_sc; @@ -679,22 +683,12 @@ static void handle_multichannel_storage(struct hv_device *device, int max_chns) request = &stor_device->init_request; vstor_packet = &request->vstor_packet; - stor_device->open_sub_channel = true; /* * Establish a handler for dealing with subchannels. */ vmbus_set_sc_create_callback(device->channel, handle_sc_creation); /* - * Check to see if sub-channels have already been created. This - * can happen when this driver is re-loaded after unloading. - */ - - if (vmbus_are_subchannels_present(device->channel)) - return; - - stor_device->open_sub_channel = false; - /* * Request the host to create sub-channels. */ memset(request, 0, sizeof(struct storvsc_cmd_request)); @@ -710,23 +704,29 @@ static void handle_multichannel_storage(struct hv_device *device, int max_chns) VM_PKT_DATA_INBAND, VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED); - if (ret != 0) + if (ret != 0) { + dev_err(dev, "Failed to create sub-channel: err=%d\n", ret); return; + } t = wait_for_completion_timeout(&request->wait_event, 10*HZ); - if (t == 0) + if (t == 0) { + dev_err(dev, "Failed to create sub-channel: timed out\n"); return; + } if (vstor_packet->operation != VSTOR_OPERATION_COMPLETE_IO || - vstor_packet->status != 0) + vstor_packet->status != 0) { + dev_err(dev, "Failed to create sub-channel: op=%d, sts=%d\n", + vstor_packet->operation, vstor_packet->status); return; + } /* - * Now that we created the sub-channels, invoke the check; this - * may trigger the callback. + * We need to do nothing here, because vmbus_process_offer() + * invokes channel->sc_creation_callback, which will open and use + * the sub-channel(s). */ - stor_device->open_sub_channel = true; - vmbus_are_subchannels_present(device->channel); } static void cache_wwn(struct storvsc_device *stor_device, @@ -1794,7 +1794,6 @@ static int storvsc_probe(struct hv_device *device, } stor_device->destroy = false; - stor_device->open_sub_channel = false; init_waitqueue_head(&stor_device->waiting_to_drain); stor_device->device = device; stor_device->host = host; |