From 14948e39445db674516ccabdf01090586ecfdc9b Mon Sep 17 00:00:00 2001 From: Kimberly Brown Date: Thu, 14 Mar 2019 16:05:15 -0400 Subject: [PATCH] Drivers: hv: vmbus: Fix race condition with new ring_buffer_info mutex Fix a race condition that can result in a ring buffer pointer being set to null while a "_show" function is reading the ring buffer's data. This problem was discussed here: https://lkml.org/lkml/2018/10/18/779 To fix the race condition, add a new mutex lock to the "hv_ring_buffer_info" struct. Add a new function, "hv_ringbuffer_pre_init()", where a channel's inbound and outbound ring_buffer_info mutex locks are initialized. Acquire/release the locks in the "hv_ringbuffer_cleanup()" function, which is where the ring buffer pointers are set to null. Acquire/release the locks in the four channel-level "_show" functions that access ring buffer data. Remove the "const" qualifier from the "vmbus_channel" parameter and the "rbi" variable of the channel-level "_show" functions so that the locks can be acquired/released in these functions. Acquire/release the locks in hv_ringbuffer_get_debuginfo(). Remove the "const" qualifier from the "hv_ring_buffer_info" parameter so that the locks can be acquired/released in this function. Signed-off-by: Kimberly Brown Reviewed-by: Michael Kelley Signed-off-by: Sasha Levin --- drivers/hv/channel_mgmt.c | 2 + drivers/hv/hyperv_vmbus.h | 1 + drivers/hv/ring_buffer.c | 19 ++++++++- drivers/hv/vmbus_drv.c | 82 +++++++++++++++++++++++++-------------- include/linux/hyperv.h | 7 +++- 5 files changed, 79 insertions(+), 32 deletions(-) diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c index d32cac501fc7..3fc0b247a807 100644 --- a/drivers/hv/channel_mgmt.c +++ b/drivers/hv/channel_mgmt.c @@ -336,6 +336,8 @@ static struct vmbus_channel *alloc_channel(void) tasklet_init(&channel->callback_event, vmbus_on_event, (unsigned long)channel); + hv_ringbuffer_pre_init(channel); + return channel; } diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h index a94aab94e0b5..e5467b821f41 100644 --- a/drivers/hv/hyperv_vmbus.h +++ b/drivers/hv/hyperv_vmbus.h @@ -193,6 +193,7 @@ extern void hv_synic_clockevents_cleanup(void); /* Interface */ +void hv_ringbuffer_pre_init(struct vmbus_channel *channel); int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info, struct page *pages, u32 pagecnt); diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c index 0386ff48c5ea..121a01c43298 100644 --- a/drivers/hv/ring_buffer.c +++ b/drivers/hv/ring_buffer.c @@ -166,14 +166,18 @@ hv_get_ringbuffer_availbytes(const struct hv_ring_buffer_info *rbi, } /* Get various debug metrics for the specified ring buffer. */ -int hv_ringbuffer_get_debuginfo(const struct hv_ring_buffer_info *ring_info, +int hv_ringbuffer_get_debuginfo(struct hv_ring_buffer_info *ring_info, struct hv_ring_buffer_debug_info *debug_info) { u32 bytes_avail_towrite; u32 bytes_avail_toread; - if (!ring_info->ring_buffer) + mutex_lock(&ring_info->ring_buffer_mutex); + + if (!ring_info->ring_buffer) { + mutex_unlock(&ring_info->ring_buffer_mutex); return -EINVAL; + } hv_get_ringbuffer_availbytes(ring_info, &bytes_avail_toread, @@ -184,10 +188,19 @@ int hv_ringbuffer_get_debuginfo(const struct hv_ring_buffer_info *ring_info, debug_info->current_write_index = ring_info->ring_buffer->write_index; debug_info->current_interrupt_mask = ring_info->ring_buffer->interrupt_mask; + mutex_unlock(&ring_info->ring_buffer_mutex); + return 0; } EXPORT_SYMBOL_GPL(hv_ringbuffer_get_debuginfo); +/* Initialize a channel's ring buffer info mutex locks */ +void hv_ringbuffer_pre_init(struct vmbus_channel *channel) +{ + mutex_init(&channel->inbound.ring_buffer_mutex); + mutex_init(&channel->outbound.ring_buffer_mutex); +} + /* Initialize the ring buffer. */ int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info, struct page *pages, u32 page_cnt) @@ -240,8 +253,10 @@ int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info, /* Cleanup the ring buffer. */ void hv_ringbuffer_cleanup(struct hv_ring_buffer_info *ring_info) { + mutex_lock(&ring_info->ring_buffer_mutex); vunmap(ring_info->ring_buffer); ring_info->ring_buffer = NULL; + mutex_unlock(&ring_info->ring_buffer_mutex); } /* Write to the ring buffer. */ diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c index 6aa79b6a6750..aa25f3bcbdea 100644 --- a/drivers/hv/vmbus_drv.c +++ b/drivers/hv/vmbus_drv.c @@ -1410,7 +1410,7 @@ static void vmbus_chan_release(struct kobject *kobj) struct vmbus_chan_attribute { struct attribute attr; - ssize_t (*show)(const struct vmbus_channel *chan, char *buf); + ssize_t (*show)(struct vmbus_channel *chan, char *buf); ssize_t (*store)(struct vmbus_channel *chan, const char *buf, size_t count); }; @@ -1429,7 +1429,7 @@ static ssize_t vmbus_chan_attr_show(struct kobject *kobj, { const struct vmbus_chan_attribute *attribute = container_of(attr, struct vmbus_chan_attribute, attr); - const struct vmbus_channel *chan + struct vmbus_channel *chan = container_of(kobj, struct vmbus_channel, kobj); if (!attribute->show) @@ -1442,57 +1442,81 @@ static const struct sysfs_ops vmbus_chan_sysfs_ops = { .show = vmbus_chan_attr_show, }; -static ssize_t out_mask_show(const struct vmbus_channel *channel, char *buf) +static ssize_t out_mask_show(struct vmbus_channel *channel, char *buf) { - const struct hv_ring_buffer_info *rbi = &channel->outbound; + struct hv_ring_buffer_info *rbi = &channel->outbound; + ssize_t ret; - if (!rbi->ring_buffer) + mutex_lock(&rbi->ring_buffer_mutex); + if (!rbi->ring_buffer) { + mutex_unlock(&rbi->ring_buffer_mutex); return -EINVAL; + } - return sprintf(buf, "%u\n", rbi->ring_buffer->interrupt_mask); + ret = sprintf(buf, "%u\n", rbi->ring_buffer->interrupt_mask); + mutex_unlock(&rbi->ring_buffer_mutex); + return ret; } static VMBUS_CHAN_ATTR_RO(out_mask); -static ssize_t in_mask_show(const struct vmbus_channel *channel, char *buf) +static ssize_t in_mask_show(struct vmbus_channel *channel, char *buf) { - const struct hv_ring_buffer_info *rbi = &channel->inbound; + struct hv_ring_buffer_info *rbi = &channel->inbound; + ssize_t ret; - if (!rbi->ring_buffer) + mutex_lock(&rbi->ring_buffer_mutex); + if (!rbi->ring_buffer) { + mutex_unlock(&rbi->ring_buffer_mutex); return -EINVAL; + } - return sprintf(buf, "%u\n", rbi->ring_buffer->interrupt_mask); + ret = sprintf(buf, "%u\n", rbi->ring_buffer->interrupt_mask); + mutex_unlock(&rbi->ring_buffer_mutex); + return ret; } static VMBUS_CHAN_ATTR_RO(in_mask); -static ssize_t read_avail_show(const struct vmbus_channel *channel, char *buf) +static ssize_t read_avail_show(struct vmbus_channel *channel, char *buf) { - const struct hv_ring_buffer_info *rbi = &channel->inbound; + struct hv_ring_buffer_info *rbi = &channel->inbound; + ssize_t ret; - if (!rbi->ring_buffer) + mutex_lock(&rbi->ring_buffer_mutex); + if (!rbi->ring_buffer) { + mutex_unlock(&rbi->ring_buffer_mutex); return -EINVAL; + } - return sprintf(buf, "%u\n", hv_get_bytes_to_read(rbi)); + ret = sprintf(buf, "%u\n", hv_get_bytes_to_read(rbi)); + mutex_unlock(&rbi->ring_buffer_mutex); + return ret; } static VMBUS_CHAN_ATTR_RO(read_avail); -static ssize_t write_avail_show(const struct vmbus_channel *channel, char *buf) +static ssize_t write_avail_show(struct vmbus_channel *channel, char *buf) { - const struct hv_ring_buffer_info *rbi = &channel->outbound; + struct hv_ring_buffer_info *rbi = &channel->outbound; + ssize_t ret; - if (!rbi->ring_buffer) + mutex_lock(&rbi->ring_buffer_mutex); + if (!rbi->ring_buffer) { + mutex_unlock(&rbi->ring_buffer_mutex); return -EINVAL; + } - return sprintf(buf, "%u\n", hv_get_bytes_to_write(rbi)); + ret = sprintf(buf, "%u\n", hv_get_bytes_to_write(rbi)); + mutex_unlock(&rbi->ring_buffer_mutex); + return ret; } static VMBUS_CHAN_ATTR_RO(write_avail); -static ssize_t show_target_cpu(const struct vmbus_channel *channel, char *buf) +static ssize_t show_target_cpu(struct vmbus_channel *channel, char *buf) { return sprintf(buf, "%u\n", channel->target_cpu); } static VMBUS_CHAN_ATTR(cpu, S_IRUGO, show_target_cpu, NULL); -static ssize_t channel_pending_show(const struct vmbus_channel *channel, +static ssize_t channel_pending_show(struct vmbus_channel *channel, char *buf) { return sprintf(buf, "%d\n", @@ -1501,7 +1525,7 @@ static ssize_t channel_pending_show(const struct vmbus_channel *channel, } static VMBUS_CHAN_ATTR(pending, S_IRUGO, channel_pending_show, NULL); -static ssize_t channel_latency_show(const struct vmbus_channel *channel, +static ssize_t channel_latency_show(struct vmbus_channel *channel, char *buf) { return sprintf(buf, "%d\n", @@ -1510,19 +1534,19 @@ static ssize_t channel_latency_show(const struct vmbus_channel *channel, } static VMBUS_CHAN_ATTR(latency, S_IRUGO, channel_latency_show, NULL); -static ssize_t channel_interrupts_show(const struct vmbus_channel *channel, char *buf) +static ssize_t channel_interrupts_show(struct vmbus_channel *channel, char *buf) { return sprintf(buf, "%llu\n", channel->interrupts); } static VMBUS_CHAN_ATTR(interrupts, S_IRUGO, channel_interrupts_show, NULL); -static ssize_t channel_events_show(const struct vmbus_channel *channel, char *buf) +static ssize_t channel_events_show(struct vmbus_channel *channel, char *buf) { return sprintf(buf, "%llu\n", channel->sig_events); } static VMBUS_CHAN_ATTR(events, S_IRUGO, channel_events_show, NULL); -static ssize_t channel_intr_in_full_show(const struct vmbus_channel *channel, +static ssize_t channel_intr_in_full_show(struct vmbus_channel *channel, char *buf) { return sprintf(buf, "%llu\n", @@ -1530,7 +1554,7 @@ static ssize_t channel_intr_in_full_show(const struct vmbus_channel *channel, } static VMBUS_CHAN_ATTR(intr_in_full, 0444, channel_intr_in_full_show, NULL); -static ssize_t channel_intr_out_empty_show(const struct vmbus_channel *channel, +static ssize_t channel_intr_out_empty_show(struct vmbus_channel *channel, char *buf) { return sprintf(buf, "%llu\n", @@ -1538,7 +1562,7 @@ static ssize_t channel_intr_out_empty_show(const struct vmbus_channel *channel, } static VMBUS_CHAN_ATTR(intr_out_empty, 0444, channel_intr_out_empty_show, NULL); -static ssize_t channel_out_full_first_show(const struct vmbus_channel *channel, +static ssize_t channel_out_full_first_show(struct vmbus_channel *channel, char *buf) { return sprintf(buf, "%llu\n", @@ -1546,7 +1570,7 @@ static ssize_t channel_out_full_first_show(const struct vmbus_channel *channel, } static VMBUS_CHAN_ATTR(out_full_first, 0444, channel_out_full_first_show, NULL); -static ssize_t channel_out_full_total_show(const struct vmbus_channel *channel, +static ssize_t channel_out_full_total_show(struct vmbus_channel *channel, char *buf) { return sprintf(buf, "%llu\n", @@ -1554,14 +1578,14 @@ static ssize_t channel_out_full_total_show(const struct vmbus_channel *channel, } static VMBUS_CHAN_ATTR(out_full_total, 0444, channel_out_full_total_show, NULL); -static ssize_t subchannel_monitor_id_show(const struct vmbus_channel *channel, +static ssize_t subchannel_monitor_id_show(struct vmbus_channel *channel, char *buf) { return sprintf(buf, "%u\n", channel->offermsg.monitorid); } static VMBUS_CHAN_ATTR(monitor_id, S_IRUGO, subchannel_monitor_id_show, NULL); -static ssize_t subchannel_id_show(const struct vmbus_channel *channel, +static ssize_t subchannel_id_show(struct vmbus_channel *channel, char *buf) { return sprintf(buf, "%u\n", diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h index 64698ec8f2ac..8b9a93c99c9b 100644 --- a/include/linux/hyperv.h +++ b/include/linux/hyperv.h @@ -141,6 +141,11 @@ struct hv_ring_buffer_info { u32 ring_datasize; /* < ring_size */ u32 priv_read_index; + /* + * The ring buffer mutex lock. This lock prevents the ring buffer from + * being freed while the ring buffer is being accessed. + */ + struct mutex ring_buffer_mutex; }; @@ -1206,7 +1211,7 @@ struct hv_ring_buffer_debug_info { }; -int hv_ringbuffer_get_debuginfo(const struct hv_ring_buffer_info *ring_info, +int hv_ringbuffer_get_debuginfo(struct hv_ring_buffer_info *ring_info, struct hv_ring_buffer_debug_info *debug_info); /* Vmbus interface */