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    Subject[PATCH 2.6.24-rc8-mm1 10/15] (RFC) IPC: new IPC_SETID command to modify an ID
    From: Pierre Peiffer <pierre.peiffer@bull.net>

    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@bull.net>
    Acked-by: Serge Hallyn <serue@us.ibm.com>
    ---

    include/linux/ipc.h | 9 +++++----
    ipc/compat.c | 3 +++
    ipc/msg.c | 27 ++++++++++++++++++++++++++-
    ipc/sem.c | 27 ++++++++++++++++++++++++++-
    ipc/shm.c | 27 ++++++++++++++++++++++++++-
    security/selinux/hooks.c | 3 +++
    6 files changed, 89 insertions(+), 7 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/compat.c
    ===================================================================
    --- a/ipc/compat.c
    +++ b/ipc/compat.c
    @@ -253,6 +253,7 @@ long compat_sys_semctl(int first, int se
    switch (third & (~IPC_64)) {
    case IPC_INFO:
    case IPC_RMID:
    + case IPC_SETID:
    case SEM_INFO:
    case GETVAL:
    case GETPID:
    @@ -425,6 +426,7 @@ long compat_sys_msgctl(int first, int se
    switch (second & (~IPC_64)) {
    case IPC_INFO:
    case IPC_RMID:
    + case IPC_SETID:
    case MSG_INFO:
    err = sys_msgctl(first, second, uptr);
    break;
    @@ -597,6 +599,7 @@ long compat_sys_shmctl(int first, int se

    switch (second & (~IPC_64)) {
    case IPC_RMID:
    + case IPC_SETID:
    case SHM_LOCK:
    case SHM_UNLOCK:
    err = sys_shmctl(first, second, uptr);
    Index: b/ipc/msg.c
    ===================================================================
    --- a/ipc/msg.c
    +++ b/ipc/msg.c
    @@ -329,7 +329,8 @@ retry:
    msg_unlock(msq);
    up_write(&msg_ids(ns).rw_mutex);

    - /* ipc_chid may return -EAGAIN in case of memory requirement */
    + /* msg_chid_nolock may return -EAGAIN if there is no more free idr
    + entry, just go and retry by filling again de idr cache */
    if (err == -EAGAIN)
    goto retry;

    @@ -465,6 +466,9 @@ static int msgctl_down(struct ipc_namesp
    */
    ss_wakeup(&msq->q_senders, 0);
    break;
    + case IPC_SETID:
    + err = msg_chid_nolock(ns, msq, (int)(long)buf);
    + break;
    default:
    err = -EINVAL;
    }
    @@ -475,6 +479,24 @@ out_up:
    return err;
    }

    +static int msgctl_setid(struct ipc_namespace *ns, int msqid, int cmd,
    + struct msqid_ds __user *buf, int version)
    +{
    + int err;
    +retry:
    + err = idr_pre_get(&msg_ids(ns).ipcs_idr, GFP_KERNEL);
    + if (!err)
    + return -ENOMEM;
    +
    + err = msgctl_down(ns, msqid, cmd, buf, version);
    +
    + /* msgctl_down may return -EAGAIN if there is no more free idr
    + entry, just go and retry by filling again de idr cache */
    + if (err == -EAGAIN)
    + goto retry;
    + return err;
    +}
    +
    asmlinkage long sys_msgctl(int msqid, int cmd, struct msqid_ds __user *buf)
    {
    struct msg_queue *msq;
    @@ -575,6 +597,9 @@ asmlinkage long sys_msgctl(int msqid, in
    case IPC_RMID:
    err = msgctl_down(ns, msqid, cmd, buf, version);
    return err;
    + case IPC_SETID:
    + err = msgctl_setid(ns, msqid, cmd, buf, version);
    + return err;
    default:
    return -EINVAL;
    }
    Index: b/ipc/sem.c
    ===================================================================
    --- a/ipc/sem.c
    +++ b/ipc/sem.c
    @@ -608,7 +608,8 @@ retry:
    sem_unlock(sma);
    up_write(&sem_ids(ns).rw_mutex);

    - /* ipc_chid may return -EAGAIN in case of memory requirement */
    + /* sem_chid_nolock may return -EAGAIN if there is no more free idr
    + entry, just go and retry by filling again de idr cache */
    if (err == -EAGAIN)
    goto retry;

    @@ -935,6 +936,9 @@ static int semctl_down(struct ipc_namesp
    ipc_update_perm(&semid64.sem_perm, ipcp);
    sma->sem_ctime = get_seconds();
    break;
    + case IPC_SETID:
    + err = sem_chid_nolock(ns, sma, (int)arg.val);
    + break;
    default:
    err = -EINVAL;
    }
    @@ -946,6 +950,24 @@ out_up:
    return err;
    }

    +static int semctl_setid(struct ipc_namespace *ns, int semid,
    + int cmd, int version, union semun arg)
    +{
    + int err;
    +retry:
    + err = idr_pre_get(&sem_ids(ns).ipcs_idr, GFP_KERNEL);
    + if (!err)
    + return -ENOMEM;
    +
    + err = semctl_down(ns, semid, cmd, version, arg);
    +
    + /* semctl_down may return -EAGAIN if there is no more free idr
    + entry, just go and retry by filling again de idr cache */
    + if (err == -EAGAIN)
    + goto retry;
    + return err;
    +}
    +
    asmlinkage long sys_semctl (int semid, int semnum, int cmd, union semun arg)
    {
    int err = -EINVAL;
    @@ -978,6 +1000,9 @@ asmlinkage long sys_semctl (int semid, i
    case IPC_SET:
    err = semctl_down(ns, semid, cmd, version, arg);
    return err;
    + case IPC_SETID:
    + err = semctl_setid(ns, semid, cmd, version, arg);
    + return err;
    default:
    return -EINVAL;
    }
    Index: b/ipc/shm.c
    ===================================================================
    --- a/ipc/shm.c
    +++ b/ipc/shm.c
    @@ -202,7 +202,8 @@ retry:
    shm_unlock(shp);
    up_write(&shm_ids(ns).rw_mutex);

    - /* ipc_chid may return -EAGAIN in case of memory requirement */
    + /* shm_chid_nolock may return -EAGAIN if there is no more free idr
    + entry, just go and retry by filling again de idr cache */
    if (err == -EAGAIN)
    goto retry;

    @@ -679,6 +680,9 @@ static int shmctl_down(struct ipc_namesp
    ipc_update_perm(&shmid64.shm_perm, ipcp);
    shp->shm_ctim = get_seconds();
    break;
    + case IPC_SETID:
    + err = shm_chid_nolock(ns, shp, (int)(long)buf);
    + break;
    default:
    err = -EINVAL;
    }
    @@ -689,6 +693,24 @@ out_up:
    return err;
    }

    +static int shmctl_setid(struct ipc_namespace *ns, int shmid, int cmd,
    + struct shmid_ds __user *buf, int version)
    +{
    + int err;
    +retry:
    + err = idr_pre_get(&shm_ids(ns).ipcs_idr, GFP_KERNEL);
    + if (!err)
    + return -ENOMEM;
    +
    + err = shmctl_down(ns, shmid, cmd, buf, version);
    +
    + /* shmctl_down may return -EAGAIN if there is no more free idr
    + entry, just go and retry by filling again de idr cache */
    + if (err == -EAGAIN)
    + goto retry;
    + return err;
    +}
    +
    asmlinkage long sys_shmctl(int shmid, int cmd, struct shmid_ds __user *buf)
    {
    struct shmid_kernel *shp;
    @@ -850,6 +872,9 @@ asmlinkage long sys_shmctl(int shmid, in
    case IPC_SET:
    err = shmctl_down(ns, shmid, cmd, buf, version);
    return err;
    + case IPC_SETID:
    + err = shmctl_setid(ns, shmid, cmd, buf, version);
    + return err;
    default:
    return -EINVAL;
    }
    Index: b/security/selinux/hooks.c
    ===================================================================
    --- a/security/selinux/hooks.c
    +++ b/security/selinux/hooks.c
    @@ -4651,6 +4651,7 @@ 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:
    @@ -4799,6 +4800,7 @@ 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:
    @@ -4910,6 +4912,7 @@ static int selinux_sem_semctl(struct sem
    perms = SEM__DESTROY;
    break;
    case IPC_SET:
    + case IPC_SETID:
    perms = SEM__SETATTR;
    break;
    case IPC_STAT:
    --
    Pierre Peiffer


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