[Devel] Re: [RFC][PATCH 2.6.22-rc5] System V IPC: new IPC_SETID command to modify an ID
Cedric Le Goater
clg at fr.ibm.com
Tue Jun 19 07:14:32 PDT 2007
Pierre Peiffer wrote:
> This patch adds a new IPC_SETID command to the System V IPCs set of
> commands, which allows to change the ID of an existing IPC.
>
> This command can be used through the semctl/shmctl/msgctl API, with the new
> ID passed as the third argument for msgctl and shmctl (instead of a
> pointer) and through the fourth argument for semctl.
>
> To be successful, the following rules must be respected:
> - the IPC exists
> - the user must be allowed to change the IPC attributes regarding the IPC
> permissions.
> - the new ID must satisfy the ID computation rule.
> - the entry (in the kernel internal table of IPCs) corresponding to the new
> ID must be free.
That's an interesting way to reset the ids of sysv ipcs during a restart (after
a checkpoint) and we're looking for ways to do that among other things.
How does it fit openvz ? Is it something openvz could use ?
thanks,
C.
> Signed-off-by: Pierre Peiffer <pierre.peiffer at bull.net>
>
> ---
> include/linux/ipc.h | 9 +++----
> ipc/msg.c | 16 ++++++++++++
> ipc/sem.c | 15 +++++++++++
> ipc/shm.c | 36 ++++++++++++++++++++++++++++
> ipc/util.c | 60
> +++++++++++++++++++++++++++++++++++++++++++++++
> ipc/util.h | 1
> security/selinux/hooks.c | 3 ++
> 7 files changed, 136 insertions(+), 4 deletions(-)
>
> Index: b/include/linux/ipc.h
> ===================================================================
> --- a/include/linux/ipc.h
> +++ b/include/linux/ipc.h
> @@ -35,10 +35,11 @@ struct ipc_perm
> * Control commands used with semctl, msgctl and shmctl
> * see also specific commands in sem.h, msg.h and shm.h
> */
> -#define IPC_RMID 0 /* remove resource */
> -#define IPC_SET 1 /* set ipc_perm options */
> -#define IPC_STAT 2 /* get ipc_perm options */
> -#define IPC_INFO 3 /* see ipcs */
> +#define IPC_RMID 0 /* remove resource */
> +#define IPC_SET 1 /* set ipc_perm options */
> +#define IPC_STAT 2 /* get ipc_perm options */
> +#define IPC_INFO 3 /* see ipcs */
> +#define IPC_SETID 4 /* set ipc ID */
>
> /*
> * Version flags for semctl, msgctl, and shmctl commands
> Index: b/ipc/msg.c
> ===================================================================
> --- a/ipc/msg.c
> +++ b/ipc/msg.c
> @@ -491,6 +491,7 @@ asmlinkage long sys_msgctl(int msqid, in
> if (copy_msqid_from_user(&setbuf, buf, version))
> return -EFAULT;
> break;
> + case IPC_SETID:
> case IPC_RMID:
> break;
> default:
> @@ -553,6 +554,21 @@ asmlinkage long sys_msgctl(int msqid, in
> msg_unlock(msq);
> break;
> }
> + case IPC_SETID:
> + {
> + int nid = (int)buf;
> +
> + err = ipc_mvid(&msg_ids(ns), msq->q_id,
> + nid, ns->msg_ctlmni);
> +
> + if (err)
> + goto out_unlock_up;
> +
> + msq->q_id = nid;
> + msq->q_ctime = get_seconds();
> + msg_unlock(msq);
> + break;
> + }
> case IPC_RMID:
> freeque(ns, msq, msqid);
> break;
> Index: b/ipc/sem.c
> ===================================================================
> --- a/ipc/sem.c
> +++ b/ipc/sem.c
> @@ -908,6 +908,20 @@ static int semctl_down(struct ipc_namesp
> sem_unlock(sma);
> err = 0;
> break;
> + case IPC_SETID:
> + {
> + int nid = (int)arg.val;
> + err = ipc_mvid(&sem_ids(ns), semid,
> + nid, ns->sc_semmni);
> +
> + if (err)
> + goto out_unlock;
> +
> + sma->sem_id = nid;
> + sma->sem_ctime = get_seconds();
> + sem_unlock(sma);
> + break;
> + }
> default:
> sem_unlock(sma);
> err = -EINVAL;
> @@ -950,6 +964,7 @@ asmlinkage long sys_semctl (int semid, i
> return err;
> case IPC_RMID:
> case IPC_SET:
> + case IPC_SETID:
> mutex_lock(&sem_ids(ns).mutex);
> err = semctl_down(ns,semid,semnum,cmd,version,arg);
> mutex_unlock(&sem_ids(ns).mutex);
> Index: b/ipc/util.c
> ===================================================================
> --- a/ipc/util.c
> +++ b/ipc/util.c
> @@ -327,6 +327,66 @@ found:
> }
>
> /**
> + * ipc_mvid - move an IPC identifier
> + * @ids: IPC identifier set
> + * @oldid: ID of the IPC permission set to move
> + * @newid: new ID of the IPC permission set to move
> + * @size: new size limit for the id array
> + *
> + * Move an entry in the IPC arrays from the 'oldid' place to the
> + * 'newid' place. The seq number of the entry is updated to match the
> + * 'newid' value.
> + *
> + * Called with the list lock and ipc_ids.mutex held.
> + */
> +
> +int ipc_mvid(struct ipc_ids *ids, int oldid, int newid, int size)
> +{
> + struct kern_ipc_perm *p;
> + int old_lid = oldid % SEQ_MULTIPLIER;
> + int new_lid = newid % SEQ_MULTIPLIER;
> +
> + if ((new_lid >= size) ||
> + newid != (new_lid + (newid/SEQ_MULTIPLIER)*SEQ_MULTIPLIER))
> + return -ERANGE;
> +
> + size = grow_ary(ids,size);
> +
> + BUG_ON(old_lid >= ids->entries->size);
> +
> + p = ids->entries->p[old_lid];
> +
> + if (!p)
> + return -ENXIO;
> +
> + /*
> + * The id (n° of the entry in the table entries) may be the same
> + * but not the seq number.
> + */
> + if (new_lid != old_lid) {
> +
> + if (ids->entries->p[new_lid])
> + return -EBUSY;
> +
> + ids->entries->p[new_lid] = p;
> +
> + ids->entries->p[old_lid] = NULL;
> +
> + if (new_lid > ids->max_id)
> + ids->max_id = new_lid;
> + if (old_lid == ids->max_id) {
> + do {
> + --old_lid;
> + } while (ids->entries->p[old_lid] == NULL);
> + ids->max_id = old_lid;
> + }
> + }
> +
> + p->seq = newid/SEQ_MULTIPLIER;
> + return 0;
> +}
> +
> +/**
> * ipc_rmid - remove an IPC identifier
> * @ids: identifier set
> * @id: Identifier to remove
> Index: b/ipc/util.h
> ===================================================================
> --- a/ipc/util.h
> +++ b/ipc/util.h
> @@ -63,6 +63,7 @@ int ipc_findkey(struct ipc_ids* ids, key
> int ipc_addid(struct ipc_ids* ids, struct kern_ipc_perm* new, int size);
>
> /* must be called with both locks acquired. */
> +int ipc_mvid(struct ipc_ids *ids, int oldid, int newid, int size);
> struct kern_ipc_perm* ipc_rmid(struct ipc_ids* ids, int id);
>
> int ipcperms (struct kern_ipc_perm *ipcp, short flg);
> Index: b/security/selinux/hooks.c
> ===================================================================
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -4152,6 +4152,7 @@ static int selinux_msg_queue_msgctl(stru
> perms = MSGQ__GETATTR | MSGQ__ASSOCIATE;
> break;
> case IPC_SET:
> + case IPC_SETID:
> perms = MSGQ__SETATTR;
> break;
> case IPC_RMID:
> @@ -4300,6 +4301,7 @@ static int selinux_shm_shmctl(struct shm
> perms = SHM__GETATTR | SHM__ASSOCIATE;
> break;
> case IPC_SET:
> + case IPC_SETID:
> perms = SHM__SETATTR;
> break;
> case SHM_LOCK:
> @@ -4411,6 +4413,7 @@ static int selinux_sem_semctl(struct sem
> perms = SEM__DESTROY;
> break;
> case IPC_SET:
> + case IPC_SETID:
> perms = SEM__SETATTR;
> break;
> case IPC_STAT:
> Index: b/ipc/shm.c
> ===================================================================
> --- a/ipc/shm.c
> +++ b/ipc/shm.c
> @@ -809,6 +809,42 @@ asmlinkage long sys_shmctl (int shmid, i
> break;
> }
>
> + case IPC_SETID:
> + {
> + int nid = (int)buf;
> + mutex_lock(&shm_ids(ns).mutex);
> + shp = shm_lock(ns, shmid);
> + err = -EINVAL;
> + if(shp == NULL)
> + goto out_up;
> + err = shm_checkid(ns, shp,shmid);
> + if(err)
> + goto out_unlock_up;
> + err = audit_ipc_obj(&(shp->shm_perm));
> + if (err)
> + goto out_unlock_up;
> +
> + err = -EPERM;
> + if (current->euid != shp->shm_perm.uid &&
> + current->euid != shp->shm_perm.cuid &&
> + !capable(CAP_SYS_ADMIN))
> + goto out_unlock_up;
> +
> + err = security_shm_shmctl(shp, cmd);
> + if (err)
> + goto out_unlock_up;
> +
> + err = ipc_mvid(&shm_ids(ns), shp->id,
> + nid, ns->shm_ctlmni);
> +
> + if (err)
> + goto out_unlock_up;
> +
> + shp->id = nid;
> + shp->shm_ctim = get_seconds();
> + break;
> + }
> +
> default:
> err = -EINVAL;
> goto out;
>
_______________________________________________
Containers mailing list
Containers at lists.linux-foundation.org
https://lists.linux-foundation.org/mailman/listinfo/containers
More information about the Devel
mailing list