[RFC][PATCH 2.6.22-rc5] System V IPC: new IPC_SETID command to
modify an ID
Kirill Korotaev
dev at sw.ru
Wed Jun 20 00:13:14 PDT 2007
Cedric Le Goater wrote:
> 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 ?
my personal imho is that we should not export such interfaces to user space
and do the checkpointing from the kernel.
it simplifies a lot of things and makes checkpointing more elegant.
So until there is some user-space usage scenario of the patch I missed -
i wouldn't commit it.
Thanks,
Kirill
>
> 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;
>>
>
>
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