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    Subject[ 53/69] ipc,shm: shorten critical region for shmctl
    Date
    3.10-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Davidlohr Bueso <davidlohr.bueso@hp.com>

    commit 2caacaa82a51b78fc0c800e206473874094287ed upstream.

    With the *_INFO, *_STAT, IPC_RMID and IPC_SET commands already optimized,
    deal with the remaining SHM_LOCK and SHM_UNLOCK commands. Take the
    shm_perm lock after doing the initial auditing and security checks. The
    rest of the logic remains unchanged.

    Signed-off-by: Davidlohr Bueso <davidlohr.bueso@hp.com>
    Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
    Cc: Rik van Riel <riel@redhat.com>
    Cc: Manfred Spraul <manfred@colorfullife.com>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Mike Galbraith <efault@gmx.de>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    ipc/shm.c | 49 +++++++++++++++++++++++++------------------------
    1 file changed, 25 insertions(+), 24 deletions(-)

    --- a/ipc/shm.c
    +++ b/ipc/shm.c
    @@ -940,10 +940,8 @@ SYSCALL_DEFINE3(shmctl, int, shmid, int,
    int err, version;
    struct ipc_namespace *ns;

    - if (cmd < 0 || shmid < 0) {
    - err = -EINVAL;
    - goto out;
    - }
    + if (cmd < 0 || shmid < 0)
    + return -EINVAL;

    version = ipc_parse_version(&cmd);
    ns = current->nsproxy->ipc_ns;
    @@ -954,36 +952,40 @@ SYSCALL_DEFINE3(shmctl, int, shmid, int,
    case SHM_STAT:
    case IPC_STAT:
    return shmctl_nolock(ns, shmid, cmd, version, buf);
    + case IPC_RMID:
    + case IPC_SET:
    + return shmctl_down(ns, shmid, cmd, buf, version);
    case SHM_LOCK:
    case SHM_UNLOCK:
    {
    struct file *shm_file;

    - shp = shm_lock_check(ns, shmid);
    + rcu_read_lock();
    + shp = shm_obtain_object_check(ns, shmid);
    if (IS_ERR(shp)) {
    err = PTR_ERR(shp);
    - goto out;
    + goto out_unlock1;
    }

    audit_ipc_obj(&(shp->shm_perm));
    + err = security_shm_shmctl(shp, cmd);
    + if (err)
    + goto out_unlock1;

    + ipc_lock_object(&shp->shm_perm);
    if (!ns_capable(ns->user_ns, CAP_IPC_LOCK)) {
    kuid_t euid = current_euid();
    err = -EPERM;
    if (!uid_eq(euid, shp->shm_perm.uid) &&
    !uid_eq(euid, shp->shm_perm.cuid))
    - goto out_unlock;
    + goto out_unlock0;
    if (cmd == SHM_LOCK && !rlimit(RLIMIT_MEMLOCK))
    - goto out_unlock;
    + goto out_unlock0;
    }

    - err = security_shm_shmctl(shp, cmd);
    - if (err)
    - goto out_unlock;
    -
    shm_file = shp->shm_file;
    if (is_file_hugepages(shm_file))
    - goto out_unlock;
    + goto out_unlock0;

    if (cmd == SHM_LOCK) {
    struct user_struct *user = current_user();
    @@ -992,32 +994,31 @@ SYSCALL_DEFINE3(shmctl, int, shmid, int,
    shp->shm_perm.mode |= SHM_LOCKED;
    shp->mlock_user = user;
    }
    - goto out_unlock;
    + goto out_unlock0;
    }

    /* SHM_UNLOCK */
    if (!(shp->shm_perm.mode & SHM_LOCKED))
    - goto out_unlock;
    + goto out_unlock0;
    shmem_lock(shm_file, 0, shp->mlock_user);
    shp->shm_perm.mode &= ~SHM_LOCKED;
    shp->mlock_user = NULL;
    get_file(shm_file);
    - shm_unlock(shp);
    + ipc_unlock_object(&shp->shm_perm);
    + rcu_read_unlock();
    shmem_unlock_mapping(shm_file->f_mapping);
    +
    fput(shm_file);
    - goto out;
    - }
    - case IPC_RMID:
    - case IPC_SET:
    - err = shmctl_down(ns, shmid, cmd, buf, version);
    return err;
    + }
    default:
    return -EINVAL;
    }

    -out_unlock:
    - shm_unlock(shp);
    -out:
    +out_unlock0:
    + ipc_unlock_object(&shp->shm_perm);
    +out_unlock1:
    + rcu_read_unlock();
    return err;
    }




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