[PATCH] kni: error release device list head could cause a kernel crash.

From 3edca1e3194959ba26a6c36143f8423009661b11 Mon Sep 17 00:00:00 2001

From: zhouyangchao <redacted>
Date: Sat, 6 Aug 2016 19:14:51 +0800
Subject: [PATCH] kni: error release device list head could cause a kernel crash.

Signed-off-by: zhouyangchao <redacted>
---
 lib/librte_eal/linuxapp/kni/kni_misc.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/librte_eal/linuxapp/kni/kni_misc.c

b/lib/librte_eal/linuxapp/kni/kni_misc.c
index ae8133f..a49924b 100644

--- a/lib/librte_eal/linuxapp/kni/kni_misc.c
+++ b/lib/librte_eal/linuxapp/kni/kni_misc.c

@@ -276,8 +276,8 @@ kni_release(struct inode *inode, struct file *file)
 #ifdef RTE_KNI_VHOST
  kni_vhost_backend_release(dev);
 #endif
- kni_dev_remove(dev);
  list_del(&dev->list);
+ kni_dev_remove(dev);
  }
  up_write(&knet->kni_list_lock);

@@ -613,8 +613,8 @@ kni_ioctl_release(struct net *net,
 #ifdef RTE_KNI_VHOST
  kni_vhost_backend_release(dev);
 #endif
- kni_dev_remove(dev);
  list_del(&dev->list);
+ kni_dev_remove(dev);
  ret = 0;
  break;
  }
--

Hi,

On 8/6/2016 12:19 PM, 周杨超 wrote:

Can you please describe how crash can occur?
And if you have a crash log, can you include it?

Access to device via list, removing device from list and adding device
to list all are protected by lock (kni_list_lock), so as far as I can
see the order of removing device and removing it from list shouldn't be
a problem.

Thanks,
ferruh

On 8/8/2016 12:48 PM, Ferruh Yigit wrote:

Hi,

On 8/6/2016 12:19 PM, 周杨超 wrote:

quoted

From 3edca1e3194959ba26a6c36143f8423009661b11 Mon Sep 17 00:00:00 2001
From: zhouyangchao <redacted>
Date: Sat, 6 Aug 2016 19:14:51 +0800
Subject: [PATCH] kni: error release device list head could cause a kernel crash.

Signed-off-by: zhouyangchao <redacted>
---
 lib/librte_eal/linuxapp/kni/kni_misc.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/librte_eal/linuxapp/kni/kni_misc.c

b/lib/librte_eal/linuxapp/kni/kni_misc.c
index ae8133f..a49924b 100644

--- a/lib/librte_eal/linuxapp/kni/kni_misc.c
+++ b/lib/librte_eal/linuxapp/kni/kni_misc.c

@@ -276,8 +276,8 @@ kni_release(struct inode *inode, struct file *file)
 #ifdef RTE_KNI_VHOST
  kni_vhost_backend_release(dev);
 #endif
- kni_dev_remove(dev);
  list_del(&dev->list);
+ kni_dev_remove(dev);
  }
  up_write(&knet->kni_list_lock);

@@ -613,8 +613,8 @@ kni_ioctl_release(struct net *net,
 #ifdef RTE_KNI_VHOST
  kni_vhost_backend_release(dev);
 #endif
- kni_dev_remove(dev);
  list_del(&dev->list);
+ kni_dev_remove(dev);
  ret = 0;
  break;
  }
--

Can you please describe how crash can occur?
And if you have a crash log, can you include it?

Access to device via list, removing device from list and adding device
to list all are protected by lock (kni_list_lock), so as far as I can
see the order of removing device and removing it from list shouldn't be
a problem.

I have sent a patch to fix a crash in remove path, if you are working on
master branch this can be same issue, can you please check following patch:

http://dpdk.org/dev/patchwork/patch/15571/

Regards,
ferruh