tcmu: fix crash when remove the tcmu device
diff mbox

Message ID 1504086092-17320-1-git-send-email-lixiubo@cmss.chinamobile.com
State New, archived
Headers show

Commit Message

Xiubo Li Aug. 30, 2017, 9:41 a.m. UTC
From: Xiubo Li <lixiubo@cmss.chinamobile.com>

Before the nl REMOVE msg has been sent to the userspace, the ring's
and other resources has been released, but the userspace maybe still
using them. And then we can see the crash messages like:

ring broken, not handling completions
BUG: unable to handle kernel paging request at ffffffffffffffd0
IP: tcmu_handle_completions+0x134/0x2f0 [target_core_user]
PGD 11bdc0c067
P4D 11bdc0c067
PUD 11bdc0e067
PMD 0

Oops: 0000 [#1] SMP
cmd_id not found, ring is broken
RIP: 0010:tcmu_handle_completions+0x134/0x2f0 [target_core_user]
RSP: 0018:ffffb8a2d8983d88 EFLAGS: 00010296
RAX: 0000000000000000 RBX: ffffb8a2aaa4e000 RCX: 00000000ffffffff
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000220
R10: 0000000076c71401 R11: ffff8d2e76c713f0 R12: ffffb8a2aad56bc0
R13: 000000000000001c R14: ffff8d2e32c90000 R15: ffff8d2e76c713f0
FS:  00007f411ffff700(0000) GS:ffff8d1e7fdc0000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffd0 CR3: 0000001027070000 CR4:
00000000001406e0
Call Trace:
? tcmu_irqcontrol+0x2a/0x40 [target_core_user]
? uio_write+0x7b/0xc0 [uio]
? __vfs_write+0x37/0x150
? __getnstimeofday64+0x3b/0xd0
? vfs_write+0xb2/0x1b0
? syscall_trace_enter+0x1d0/0x2b0
? SyS_write+0x55/0xc0
? do_syscall_64+0x67/0x150
? entry_SYSCALL64_slow_path+0x25/0x25
Code: 41 5d 41 5e 41 5f 5d c3 83 f8 01 0f 85 cf 01 00
00 48 8b 7d d0 e8 dd 5c 1d f3 41 0f b7 74 24 04 48 8b
7d c8 31 d2 e8 5c c7 1b f3 <48> 8b 7d d0 49 89 c7 c6 07
00 0f 1f 40 00 4d 85 ff 0f 84 82 01  RIP:
tcmu_handle_completions+0x134/0x2f0 [target_core_user]
RSP: ffffb8a2d8983d88
CR2: ffffffffffffffd0

And the crash also could happen in tcmu_page_fault and other places.

Signed-off-by: Zhang Zhuoyu <zhangzhuoyu@cmss.chinamobile.com>
Signed-off-by: Xiubo Li <lixiubo@cmss.chinamobile.com>
---
 drivers/target/target_core_user.c | 90 +++++++++++++++++++--------------------
 1 file changed, 45 insertions(+), 45 deletions(-)

Comments

Mike Christie Sept. 1, 2017, 3:17 p.m. UTC | #1
On 08/30/2017 04:41 AM, lixiubo@cmss.chinamobile.com wrote:
> From: Xiubo Li <lixiubo@cmss.chinamobile.com>
> 
> Before the nl REMOVE msg has been sent to the userspace, the ring's
> and other resources has been released, but the userspace maybe still
> using them. And then we can see the crash messages like:
> 
> ring broken, not handling completions
> BUG: unable to handle kernel paging request at ffffffffffffffd0
> IP: tcmu_handle_completions+0x134/0x2f0 [target_core_user]
> PGD 11bdc0c067
> P4D 11bdc0c067
> PUD 11bdc0e067
> PMD 0
> 
> Oops: 0000 [#1] SMP
> cmd_id not found, ring is broken
> RIP: 0010:tcmu_handle_completions+0x134/0x2f0 [target_core_user]
> RSP: 0018:ffffb8a2d8983d88 EFLAGS: 00010296
> RAX: 0000000000000000 RBX: ffffb8a2aaa4e000 RCX: 00000000ffffffff
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
> RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000220
> R10: 0000000076c71401 R11: ffff8d2e76c713f0 R12: ffffb8a2aad56bc0
> R13: 000000000000001c R14: ffff8d2e32c90000 R15: ffff8d2e76c713f0
> FS:  00007f411ffff700(0000) GS:ffff8d1e7fdc0000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: ffffffffffffffd0 CR3: 0000001027070000 CR4:
> 00000000001406e0
> Call Trace:
> ? tcmu_irqcontrol+0x2a/0x40 [target_core_user]
> ? uio_write+0x7b/0xc0 [uio]
> ? __vfs_write+0x37/0x150
> ? __getnstimeofday64+0x3b/0xd0
> ? vfs_write+0xb2/0x1b0
> ? syscall_trace_enter+0x1d0/0x2b0
> ? SyS_write+0x55/0xc0
> ? do_syscall_64+0x67/0x150
> ? entry_SYSCALL64_slow_path+0x25/0x25
> Code: 41 5d 41 5e 41 5f 5d c3 83 f8 01 0f 85 cf 01 00
> 00 48 8b 7d d0 e8 dd 5c 1d f3 41 0f b7 74 24 04 48 8b
> 7d c8 31 d2 e8 5c c7 1b f3 <48> 8b 7d d0 49 89 c7 c6 07
> 00 0f 1f 40 00 4d 85 ff 0f 84 82 01  RIP:
> tcmu_handle_completions+0x134/0x2f0 [target_core_user]
> RSP: ffffb8a2d8983d88
> CR2: ffffffffffffffd0
> 
> And the crash also could happen in tcmu_page_fault and other places.
> 
> Signed-off-by: Zhang Zhuoyu <zhangzhuoyu@cmss.chinamobile.com>
> Signed-off-by: Xiubo Li <lixiubo@cmss.chinamobile.com>
> ---
>  drivers/target/target_core_user.c | 90 +++++++++++++++++++--------------------
>  1 file changed, 45 insertions(+), 45 deletions(-)
> 
> diff --git a/drivers/target/target_core_user.c b/drivers/target/target_core_user.c
> index 942d0942..0ff8541 100644
> --- a/drivers/target/target_core_user.c
> +++ b/drivers/target/target_core_user.c
> @@ -1280,10 +1280,55 @@ static void tcmu_dev_call_rcu(struct rcu_head *p)
>  	kfree(udev);
>  }
>  
> +static int tcmu_check_and_free_pending_cmd(struct tcmu_cmd *cmd)
> +{
> +	if (test_bit(TCMU_CMD_BIT_EXPIRED, &cmd->flags)) {
> +		kmem_cache_free(tcmu_cmd_cache, cmd);
> +		return 0;
> +	}
> +	return -EINVAL;
> +}
> +
> +static void tcmu_blocks_release(struct tcmu_dev *udev)
> +{
> +	int i;
> +	struct page *page;
> +
> +	/* Try to release all block pages */
> +	mutex_lock(&udev->cmdr_lock);
> +	for (i = 0; i <= udev->dbi_max; i++) {
> +		page = radix_tree_delete(&udev->data_blocks, i);
> +		if (page) {
> +			__free_page(page);
> +			atomic_dec(&global_db_count);
> +		}
> +	}
> +	mutex_unlock(&udev->cmdr_lock);
> +}
> +
>  static void tcmu_dev_kref_release(struct kref *kref)
>  {
>  	struct tcmu_dev *udev = container_of(kref, struct tcmu_dev, kref);
>  	struct se_device *dev = &udev->se_dev;
> +	struct tcmu_cmd *cmd;
> +	bool all_expired = true;
> +	int i;
> +
> +	vfree(udev->mb_addr);
> +
> +	/* Upper layer should drain all requests before calling this */
> +	spin_lock_irq(&udev->commands_lock);
> +	idr_for_each_entry(&udev->commands, cmd, i) {
> +		if (tcmu_check_and_free_pending_cmd(cmd) != 0)
> +			all_expired = false;
> +	}
> +	idr_destroy(&udev->commands);
> +	spin_unlock_irq(&udev->commands_lock);
> +	WARN_ON(!all_expired);
> +
> +	tcmu_blocks_release(udev);
> +
> +	uio_unregister_device(&udev->uio_info);
>  
>  	call_rcu(&dev->rcu_head, tcmu_dev_call_rcu);
>  }
> @@ -1534,37 +1579,11 @@ static int tcmu_configure_device(struct se_device *dev)
>  	return ret;
>  }
>  
> -static int tcmu_check_and_free_pending_cmd(struct tcmu_cmd *cmd)
> -{
> -	if (test_bit(TCMU_CMD_BIT_EXPIRED, &cmd->flags)) {
> -		kmem_cache_free(tcmu_cmd_cache, cmd);
> -		return 0;
> -	}
> -	return -EINVAL;
> -}
> -
>  static bool tcmu_dev_configured(struct tcmu_dev *udev)
>  {
>  	return udev->uio_info.uio_dev ? true : false;
>  }
>  
> -static void tcmu_blocks_release(struct tcmu_dev *udev)
> -{
> -	int i;
> -	struct page *page;
> -
> -	/* Try to release all block pages */
> -	mutex_lock(&udev->cmdr_lock);
> -	for (i = 0; i <= udev->dbi_max; i++) {
> -		page = radix_tree_delete(&udev->data_blocks, i);
> -		if (page) {
> -			__free_page(page);
> -			atomic_dec(&global_db_count);
> -		}
> -	}
> -	mutex_unlock(&udev->cmdr_lock);
> -}
> -
>  static void tcmu_free_device(struct se_device *dev)
>  {
>  	struct tcmu_dev *udev = TCMU_DEV(dev);
> @@ -1576,9 +1595,6 @@ static void tcmu_free_device(struct se_device *dev)
>  static void tcmu_destroy_device(struct se_device *dev)
>  {
>  	struct tcmu_dev *udev = TCMU_DEV(dev);
> -	struct tcmu_cmd *cmd;
> -	bool all_expired = true;
> -	int i;
>  
>  	del_timer_sync(&udev->timeout);
>  
> @@ -1586,24 +1602,8 @@ static void tcmu_destroy_device(struct se_device *dev)
>  	list_del(&udev->node);
>  	mutex_unlock(&root_udev_mutex);
>  
> -	vfree(udev->mb_addr);
> -
> -	/* Upper layer should drain all requests before calling this */
> -	spin_lock_irq(&udev->commands_lock);
> -	idr_for_each_entry(&udev->commands, cmd, i) {
> -		if (tcmu_check_and_free_pending_cmd(cmd) != 0)
> -			all_expired = false;
> -	}
> -	idr_destroy(&udev->commands);
> -	spin_unlock_irq(&udev->commands_lock);
> -	WARN_ON(!all_expired);
> -
> -	tcmu_blocks_release(udev);
> -

Agree the above part needs to be delayed.

>  	tcmu_netlink_event(udev, TCMU_CMD_REMOVED_DEVICE, 0, NULL);
>  
> -	uio_unregister_device(&udev->uio_info);
> -

Why does this call? After this returns userspace should have done its
close and stopped doing uio poll/read/write calls right?

If userspace is not doing that, why isn't it? I think that is a bug.

If we need to work around userspace then you need to drop the
uio_unregister_device call in tcmu_configure_device.


>  	/* release ref from configure */
>  	kref_put(&udev->kref, tcmu_dev_kref_release);
>  }
> 

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Xiubo Li Sept. 4, 2017, 2:21 a.m. UTC | #2
Hi Mike,

Sorry for late.


[...]
>> @@ -1576,9 +1595,6 @@ static void tcmu_free_device(struct se_device *dev)
>>   static void tcmu_destroy_device(struct se_device *dev)
>>   {
>>   	struct tcmu_dev *udev = TCMU_DEV(dev);
>> -	struct tcmu_cmd *cmd;
>> -	bool all_expired = true;
>> -	int i;
>>   
>>   	del_timer_sync(&udev->timeout);
>>   
>> @@ -1586,24 +1602,8 @@ static void tcmu_destroy_device(struct se_device *dev)
>>   	list_del(&udev->node);
>>   	mutex_unlock(&root_udev_mutex);
>>   
>> -	vfree(udev->mb_addr);
>> -
>> -	/* Upper layer should drain all requests before calling this */
>> -	spin_lock_irq(&udev->commands_lock);
>> -	idr_for_each_entry(&udev->commands, cmd, i) {
>> -		if (tcmu_check_and_free_pending_cmd(cmd) != 0)
>> -			all_expired = false;
>> -	}
>> -	idr_destroy(&udev->commands);
>> -	spin_unlock_irq(&udev->commands_lock);
>> -	WARN_ON(!all_expired);
>> -
>> -	tcmu_blocks_release(udev);
>> -
> Agree the above part needs to be delayed.
>
>>   	tcmu_netlink_event(udev, TCMU_CMD_REMOVED_DEVICE, 0, NULL);
>>   
>> -	uio_unregister_device(&udev->uio_info);
>> -
> Why does this call? After this returns userspace should have done its
> close and stopped doing uio poll/read/write calls right?
Do you mean after when the uio_unregister_device() returns the 
tcmu_netlink_event()
has successfully told the runner and stopped doing uio poll/read/write 
calls ?

If i have gotten yours. I will say it maybe not yet.

See the following case if without :

-	uio_unregister_device(&udev->uio_info);
-

There should still be a bug:
1, IOs are running
2, try to remove the target device through the configfs
3, then the TCMU will send a REMOVE netlink message to the runner in 
tcmu_destroy_device().
4, since there maybe lots of IOs and the runner will wait for them being 
done, which will still use the UIO device.
5, the TCMU doesn't know what the runner's status and just called 
uio_unregister_device() to release the UIO device .
6, ....

And I am not very sure will the above case will cause the kernel's 
another crash ?



> If userspace is not doing that, why isn't it? I think that is a bug.
>
> If we need to work around userspace then you need to drop the
> uio_unregister_device call in tcmu_configure_device.
>
Yes, for this patch if we move it to tcmu_dev_kfre_release(), this 
should be fixed too.

Thanks,

BRs
Xiubo



>>   	/* release ref from configure */
>>   	kref_put(&udev->kref, tcmu_dev_kref_release);
>>   }
>>



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Patch
diff mbox

diff --git a/drivers/target/target_core_user.c b/drivers/target/target_core_user.c
index 942d0942..0ff8541 100644
--- a/drivers/target/target_core_user.c
+++ b/drivers/target/target_core_user.c
@@ -1280,10 +1280,55 @@  static void tcmu_dev_call_rcu(struct rcu_head *p)
 	kfree(udev);
 }
 
+static int tcmu_check_and_free_pending_cmd(struct tcmu_cmd *cmd)
+{
+	if (test_bit(TCMU_CMD_BIT_EXPIRED, &cmd->flags)) {
+		kmem_cache_free(tcmu_cmd_cache, cmd);
+		return 0;
+	}
+	return -EINVAL;
+}
+
+static void tcmu_blocks_release(struct tcmu_dev *udev)
+{
+	int i;
+	struct page *page;
+
+	/* Try to release all block pages */
+	mutex_lock(&udev->cmdr_lock);
+	for (i = 0; i <= udev->dbi_max; i++) {
+		page = radix_tree_delete(&udev->data_blocks, i);
+		if (page) {
+			__free_page(page);
+			atomic_dec(&global_db_count);
+		}
+	}
+	mutex_unlock(&udev->cmdr_lock);
+}
+
 static void tcmu_dev_kref_release(struct kref *kref)
 {
 	struct tcmu_dev *udev = container_of(kref, struct tcmu_dev, kref);
 	struct se_device *dev = &udev->se_dev;
+	struct tcmu_cmd *cmd;
+	bool all_expired = true;
+	int i;
+
+	vfree(udev->mb_addr);
+
+	/* Upper layer should drain all requests before calling this */
+	spin_lock_irq(&udev->commands_lock);
+	idr_for_each_entry(&udev->commands, cmd, i) {
+		if (tcmu_check_and_free_pending_cmd(cmd) != 0)
+			all_expired = false;
+	}
+	idr_destroy(&udev->commands);
+	spin_unlock_irq(&udev->commands_lock);
+	WARN_ON(!all_expired);
+
+	tcmu_blocks_release(udev);
+
+	uio_unregister_device(&udev->uio_info);
 
 	call_rcu(&dev->rcu_head, tcmu_dev_call_rcu);
 }
@@ -1534,37 +1579,11 @@  static int tcmu_configure_device(struct se_device *dev)
 	return ret;
 }
 
-static int tcmu_check_and_free_pending_cmd(struct tcmu_cmd *cmd)
-{
-	if (test_bit(TCMU_CMD_BIT_EXPIRED, &cmd->flags)) {
-		kmem_cache_free(tcmu_cmd_cache, cmd);
-		return 0;
-	}
-	return -EINVAL;
-}
-
 static bool tcmu_dev_configured(struct tcmu_dev *udev)
 {
 	return udev->uio_info.uio_dev ? true : false;
 }
 
-static void tcmu_blocks_release(struct tcmu_dev *udev)
-{
-	int i;
-	struct page *page;
-
-	/* Try to release all block pages */
-	mutex_lock(&udev->cmdr_lock);
-	for (i = 0; i <= udev->dbi_max; i++) {
-		page = radix_tree_delete(&udev->data_blocks, i);
-		if (page) {
-			__free_page(page);
-			atomic_dec(&global_db_count);
-		}
-	}
-	mutex_unlock(&udev->cmdr_lock);
-}
-
 static void tcmu_free_device(struct se_device *dev)
 {
 	struct tcmu_dev *udev = TCMU_DEV(dev);
@@ -1576,9 +1595,6 @@  static void tcmu_free_device(struct se_device *dev)
 static void tcmu_destroy_device(struct se_device *dev)
 {
 	struct tcmu_dev *udev = TCMU_DEV(dev);
-	struct tcmu_cmd *cmd;
-	bool all_expired = true;
-	int i;
 
 	del_timer_sync(&udev->timeout);
 
@@ -1586,24 +1602,8 @@  static void tcmu_destroy_device(struct se_device *dev)
 	list_del(&udev->node);
 	mutex_unlock(&root_udev_mutex);
 
-	vfree(udev->mb_addr);
-
-	/* Upper layer should drain all requests before calling this */
-	spin_lock_irq(&udev->commands_lock);
-	idr_for_each_entry(&udev->commands, cmd, i) {
-		if (tcmu_check_and_free_pending_cmd(cmd) != 0)
-			all_expired = false;
-	}
-	idr_destroy(&udev->commands);
-	spin_unlock_irq(&udev->commands_lock);
-	WARN_ON(!all_expired);
-
-	tcmu_blocks_release(udev);
-
 	tcmu_netlink_event(udev, TCMU_CMD_REMOVED_DEVICE, 0, NULL);
 
-	uio_unregister_device(&udev->uio_info);
-
 	/* release ref from configure */
 	kref_put(&udev->kref, tcmu_dev_kref_release);
 }