[PATCH] eCryptFS: fix missed mutex_unlock

[PATCH] eCryptFS: fix missed mutex_unlock

[Cyrill Gorcunov]

---

Ingo, could you please apply it and test? Actually I really doubt if it help
with the locking problem you pointed. There are two procedures
in miscrev.c - ecryptfs_miscdev_poll() and ecryptfs_miscdev_read()
which takes/releases mutexes in a bit strange way... investigating,
but this patch is needed anyway.

Index: linux-2.6.git/fs/ecryptfs/crypto.c
===================================================================
--- linux-2.6.git.orig/fs/ecryptfs/crypto.c	2008-05-18 16:44:20.000000000 +0400
+++ linux-2.6.git/fs/ecryptfs/crypto.c	2008-05-18 17:56:12.000000000 +0400
@@ -1903,6 +1903,7 @@ int ecryptfs_get_tfm_and_mutex_for_ciphe
 		if (rc) {
 			printk(KERN_ERR "Error adding new key_tfm to list; "
 					"rc = [%d]\n", rc);
+			mutex_unlock(&key_tfm_list_mutex);
 			goto out;
 		}
 	}

Re: [PATCH] eCryptFS: fix missed mutex_unlock

[Andrew Morton]

On Sun, 18 May 2008 18:26:11 +0400 Cyrill Gorcunov <gorcunov@gmail.com> wrote:

> ---
> 
> Ingo, could you please apply it and test? Actually I really doubt if it help
> with the locking problem you pointed. There are two procedures
> in miscrev.c - ecryptfs_miscdev_poll() and ecryptfs_miscdev_read()
> which takes/releases mutexes in a bit strange way... investigating,
> but this patch is needed anyway.
> 
> Index: linux-2.6.git/fs/ecryptfs/crypto.c
> ===================================================================
> --- linux-2.6.git.orig/fs/ecryptfs/crypto.c	2008-05-18 16:44:20.000000000 +0400
> +++ linux-2.6.git/fs/ecryptfs/crypto.c	2008-05-18 17:56:12.000000000 +0400
> @@ -1903,6 +1903,7 @@ int ecryptfs_get_tfm_and_mutex_for_ciphe
>  		if (rc) {
>  			printk(KERN_ERR "Error adding new key_tfm to list; "
>  					"rc = [%d]\n", rc);
> +			mutex_unlock(&key_tfm_list_mutex);
>  			goto out;
>  		}
>  	}

Better to do it this way, I think:

--- a/fs/ecryptfs/crypto.c~ecryptfs-fix-missed-mutex_unlock
+++ a/fs/ecryptfs/crypto.c
@@ -1906,9 +1906,9 @@ int ecryptfs_get_tfm_and_mutex_for_ciphe
 			goto out;
 		}
 	}
-	mutex_unlock(&key_tfm_list_mutex);
 	(*tfm) = key_tfm->key_tfm;
 	(*tfm_mutex) = &key_tfm->key_tfm_mutex;
 out:
+	mutex_unlock(&key_tfm_list_mutex);
 	return rc;
 }
_

Holding the lock for an additional few instructions may not be strictly
needed, but we might avoid the reintroduction of such bugs?

Re: [PATCH] eCryptFS: fix missed mutex_unlock

[Cyrill Gorcunov]

On Tue, May 20, 2008 at 11:28 AM, Andrew Morton
<akpm@linux-foundation.org> wrote:
> On Sun, 18 May 2008 18:26:11 +0400 Cyrill Gorcunov <gorcunov@gmail.com> wrote:
>
>> ---
>>
>> Ingo, could you please apply it and test? Actually I really doubt if it help
>> with the locking problem you pointed. There are two procedures
>> in miscrev.c - ecryptfs_miscdev_poll() and ecryptfs_miscdev_read()
>> which takes/releases mutexes in a bit strange way... investigating,
>> but this patch is needed anyway.
>>
>> Index: linux-2.6.git/fs/ecryptfs/crypto.c
>> ===================================================================
>> --- linux-2.6.git.orig/fs/ecryptfs/crypto.c   2008-05-18 16:44:20.000000000 +0400
>> +++ linux-2.6.git/fs/ecryptfs/crypto.c        2008-05-18 17:56:12.000000000 +0400
>> @@ -1903,6 +1903,7 @@ int ecryptfs_get_tfm_and_mutex_for_ciphe
>>               if (rc) {
>>                       printk(KERN_ERR "Error adding new key_tfm to list; "
>>                                       "rc = [%d]\n", rc);
>> +                     mutex_unlock(&key_tfm_list_mutex);
>>                       goto out;
>>               }
>>       }
>
> Better to do it this way, I think:
>
> --- a/fs/ecryptfs/crypto.c~ecryptfs-fix-missed-mutex_unlock
> +++ a/fs/ecryptfs/crypto.c
> @@ -1906,9 +1906,9 @@ int ecryptfs_get_tfm_and_mutex_for_ciphe
>                        goto out;
>                }
>        }
> -       mutex_unlock(&key_tfm_list_mutex);
>        (*tfm) = key_tfm->key_tfm;
>        (*tfm_mutex) = &key_tfm->key_tfm_mutex;
>  out:
> +       mutex_unlock(&key_tfm_list_mutex);
>        return rc;
>  }
> _
>
> Holding the lock for an additional few instructions may not be strictly
> needed, but we might avoid the reintroduction of such bugs?
>
>

Good idea, thanks! Could you update the patch, please?

Re: [PATCH] eCryptFS: fix missed mutex_unlock

[Ingo Molnar]

* Cyrill Gorcunov <gorcunov@gmail.com> wrote:

> Ingo, could you please apply it and test? Actually I really doubt if 
> it help with the locking problem you pointed. There are two procedures 
> in miscrev.c - ecryptfs_miscdev_poll() and ecryptfs_miscdev_read() 
> which takes/releases mutexes in a bit strange way... investigating, 
> but this patch is needed anyway.

btw., i didnt do any specific ecryptfs testing - randconfig enabled it 
and it got booted. So if you dont get the warning during 
bootup/module-load, you'll have the same test coverage i did.

	Ingo

Re: [PATCH] eCryptFS: fix missed mutex_unlock

[Cyrill Gorcunov]

On Wed, May 21, 2008 at 12:02 PM, Ingo Molnar <mingo@elte.hu> wrote:
>
> * Cyrill Gorcunov <gorcunov@gmail.com> wrote:
>
>> Ingo, could you please apply it and test? Actually I really doubt if
>> it help with the locking problem you pointed. There are two procedures
>> in miscrev.c - ecryptfs_miscdev_poll() and ecryptfs_miscdev_read()
>> which takes/releases mutexes in a bit strange way... investigating,
>> but this patch is needed anyway.
>
> btw., i didnt do any specific ecryptfs testing - randconfig enabled it
> and it got booted. So if you dont get the warning during
> bootup/module-load, you'll have the same test coverage i did.
>
>        Ingo
>

oh, thanks ;)