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 general protection fault:
general protection fault: 0000 [#1] SMP
...
RIP: 0010:[<ffffffff81461b6b>] [<ffffffff81461b6b>] vmbus_on_event+0xc4/0x149
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.
Reported-by: Rolf Neugebauer <rolf.neugebauer@xxxxxxxxxx>
Signed-off-by: Dexuan Cui <decui@xxxxxxxxxxxxx>
---
drivers/hv/channel.c | 3 +++
drivers/hv/channel_mgmt.c | 20 +++++++++-----------
include/linux/hyperv.h | 3 +++
3 files changed, 15 insertions(+), 11 deletions(-)
diff --git a/drivers/hv/channel.c b/drivers/hv/channel.c
index 56dd261..7811cf9 100644
--- a/drivers/hv/channel.c
+++ b/drivers/hv/channel.c
@@ -546,8 +546,11 @@ static int vmbus_close_internal(struct vmbus_channel *channel)
put_cpu();
smp_call_function_single(channel->target_cpu, reset_channel_cb,
channel, true);
+ smp_call_function_single(channel->target_cpu,
+ percpu_channel_deq, channel, true);
} else {
reset_channel_cb(channel);
+ percpu_channel_deq(channel);
put_cpu();
}
diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
index 38b682ba..c4b5c07 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 <linux/kernel.h>
+#include <linux/interrupt.h>
#include <linux/sched.h>
#include <linux/wait.h>
#include <linux/mm.h>
@@ -277,7 +278,7 @@ static void free_channel(struct vmbus_channel *channel)
kfree(channel);
}
-static void percpu_channel_enq(void *arg)
+void percpu_channel_enq(void *arg)
{
struct vmbus_channel *channel = arg;
int cpu = smp_processor_id();
@@ -285,7 +286,7 @@ static void percpu_channel_enq(void *arg)
list_add_tail(&channel->percpu_list, &hv_context.percpu_list[cpu]);
}
-static void percpu_channel_deq(void *arg)
+void percpu_channel_deq(void *arg)
{
struct vmbus_channel *channel = arg;
@@ -313,15 +314,6 @@ void hv_process_channel_removal(struct vmbus_channel *channel, u32 relid)
BUG_ON(!channel->rescind);
BUG_ON(!mutex_is_locked(&vmbus_connection.channel_mutex));
- if (channel->target_cpu != get_cpu()) {
- put_cpu();
- smp_call_function_single(channel->target_cpu,
- percpu_channel_deq, channel, true);
- } else {
- percpu_channel_deq(channel);
- put_cpu();
- }
-
if (channel->primary_channel == NULL) {
list_del(&channel->listentry);
@@ -363,6 +355,7 @@ void vmbus_free_channels(void)
*/
static void vmbus_process_offer(struct vmbus_channel *newchannel)
{
+ struct tasklet_struct *tasklet;
struct vmbus_channel *channel;
bool fnew = true;
unsigned long flags;
@@ -409,6 +402,8 @@ static void vmbus_process_offer(struct vmbus_channel *newchannel)
init_vp_index(newchannel, dev_type);
+ tasklet = hv_context.event_dpc[newchannel->target_cpu];
+ tasklet_disable(tasklet);
if (newchannel->target_cpu != get_cpu()) {
put_cpu();
smp_call_function_single(newchannel->target_cpu,
@@ -418,6 +413,7 @@ static void vmbus_process_offer(struct vmbus_channel *newchannel)
percpu_channel_enq(newchannel);
put_cpu();
}
+ tasklet_enable(tasklet);
/*
* This state is used to indicate a successful open
@@ -469,6 +465,7 @@ static void vmbus_process_offer(struct vmbus_channel *newchannel)
list_del(&newchannel->listentry);
mutex_unlock(&vmbus_connection.channel_mutex);
+ tasklet_disable(tasklet);
if (newchannel->target_cpu != get_cpu()) {
put_cpu();
smp_call_function_single(newchannel->target_cpu,
@@ -477,6 +474,7 @@ static void vmbus_process_offer(struct vmbus_channel *newchannel)
percpu_channel_deq(newchannel);
put_cpu();
}
+ tasklet_enable(tasklet);
err_free_chan:
free_channel(newchannel);
diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
index 7be7237..95aea09 100644
--- a/include/linux/hyperv.h
+++ b/include/linux/hyperv.h
@@ -1328,6 +1328,9 @@ extern bool vmbus_prep_negotiate_resp(struct icmsg_hdr *,
struct icmsg_negotiate *, u8 *, int,
int);
+void percpu_channel_enq(void *arg);
+void percpu_channel_deq(void *arg);
+
void hv_process_channel_removal(struct vmbus_channel *channel, u32 relid);
/*
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