linux-kernel - Re: [PATCH 2/2] Merge multiple error paths in alloc

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Message-ID: <20071123131459.GB5771@linux.vnet.ibm.com>
Date:	Fri, 23 Nov 2007 18:44:59 +0530
From:	Dhaval Giani <dhaval@...ux.vnet.ibm.com>
To:	Pavel Emelyanov <xemul@...nvz.org>
Cc:	Andrew Morton <akpm@...l.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	devel@...nvz.org, Ingo Molnar <mingo@...e.hu>,
	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>
Subject: Re: [PATCH 2/2] Merge multiple error paths in alloc_uid into one

On Wed, Nov 21, 2007 at 01:53:56PM +0300, Pavel Emelyanov wrote:
> There are already 4 error paths in alloc_uid() that do incremental
> rollbacks. I think it's time to merge them. This costs us 8 lines
> of code :)
> 
> Maybe it would be better to merge this patch with the previous 
> one, but I remember that some time ago I sent a similar patch 
> (fixing the error path and cleaning it), but I was told to make 
> two patches in such cases.
> 
> Signed-off-by: Pavel Emelyanov <xemul@...nvz.org>

Looks good.

Acked-by: Dhaval Giani <dhaval@...ux.vnet.ibm.com>
> 
> ---
> 
> diff --git a/kernel/user.c b/kernel/user.c
> index 3549c4b..cb6c6f9 100644
> --- a/kernel/user.c
> +++ b/kernel/user.c
> @@ -328,7 +328,7 @@ void free_uid(struct user_struct *up)
>  struct user_struct * alloc_uid(struct user_namespace *ns, uid_t uid)
>  {
>  	struct hlist_head *hashent = uidhashentry(ns, uid);
> -	struct user_struct *up;
> +	struct user_struct *up, *new;
> 
>  	/* Make uid_hash_find() + uids_user_create() + uid_hash_insert()
>  	 * atomic.
> @@ -340,13 +340,9 @@ struct user_struct * alloc_uid(struct user_namespace *ns, uid_t uid)
>  	spin_unlock_irq(&uidhash_lock);
> 
>  	if (!up) {
> -		struct user_struct *new;
> -
>  		new = kmem_cache_alloc(uid_cachep, GFP_KERNEL);
> -		if (!new) {
> -			uids_mutex_unlock();
> -			return NULL;
> -		}
> +		if (!new)
> +			goto out_unlock;
> 
>  		new->uid = uid;
>  		atomic_set(&new->__count, 1);
> @@ -362,28 +358,14 @@ struct user_struct * alloc_uid(struct user_namespace *ns, uid_t uid)
>  #endif
>  		new->locked_shm = 0;
> 
> -		if (alloc_uid_keyring(new, current) < 0) {
> -			kmem_cache_free(uid_cachep, new);
> -			uids_mutex_unlock();
> -			return NULL;
> -		}
> +		if (alloc_uid_keyring(new, current) < 0)
> +			goto out_free_user;
> 
> -		if (sched_create_user(new) < 0) {
> -			key_put(new->uid_keyring);
> -			key_put(new->session_keyring);
> -			kmem_cache_free(uid_cachep, new);
> -			uids_mutex_unlock();
> -			return NULL;
> -		}
> +		if (sched_create_user(new) < 0)
> +			goto out_put_keys;
> 
> -		if (uids_user_create(new)) {
> -			sched_destroy_user(new);
> -			key_put(new->uid_keyring);
> -			key_put(new->session_keyring);
> -			kmem_cache_free(uid_cachep, new);
> -			uids_mutex_unlock();
> -			return NULL;
> -		}
> +		if (uids_user_create(new))
> +			goto out_destoy_sched;
> 
>  		/*
>  		 * Before adding this, check whether we raced
> @@ -411,6 +393,17 @@ struct user_struct * alloc_uid(struct user_namespace *ns, uid_t uid)
>  	uids_mutex_unlock();
> 
>  	return up;
> +
> +out_destoy_sched:
> +	sched_destroy_user(new);
> +out_put_keys:
> +	key_put(new->uid_keyring);
> +	key_put(new->session_keyring);
> +out_free_user:
> +	kmem_cache_free(uid_cachep, new);
> +out_unlock:
> +	uids_mutex_unlock();
> +	return NULL;
>  }
> 
>  void switch_uid(struct user_struct *new_user)
> -- 
> 1.5.3.4

-- 
regards,
Dhaval
-
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