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.
Signed-off-by: Pierre Peiffer <pierre.peiffer@xxxxxxxx>
---
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;
--
Pierre Peiffer
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