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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 <kimbrownkd@gmail.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Kimberly Brown 2019-03-14 16:05:15 -04:00 committed by Sasha Levin
parent 4713eb7b58
commit 14948e3944
5 changed files with 79 additions and 32 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
drivers/hv/channel_mgmt.c
View File

@ -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;
}

1
drivers/hv/hyperv_vmbus.h
View File

@ -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);

19
drivers/hv/ring_buffer.c
View File

@ -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. */

82
drivers/hv/vmbus_drv.c
View File

@ -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",

7
include/linux/hyperv.h
View File

@ -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 */