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SubjectRe: [PATCH] eCryptFS: fix missed mutex_unlock
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?



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