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[PATCH 2/2] Merge multiple error paths in alloc_uid into one [message #23636] Wed, 21 November 2007 10:53 Go to next message
Pavel Emelianov is currently offline  Pavel Emelianov
Messages: 1149
Registered: September 2006
Senior Member
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@openvz.org>

---

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
Re: [PATCH 2/2] Merge multiple error paths in alloc_uid into one [message #23732 is a reply to message #23636] Fri, 23 November 2007 13:14 Go to previous message
Dhaval Giani is currently offline  Dhaval Giani
Messages: 37
Registered: June 2007
Member
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@openvz.org>

Looks good.

Acked-by: Dhaval Giani <dhaval@linux.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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