shmctl: split the work from copyin/copyout

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 172 insertions, 175 deletions

diff --git a/ipc/shm.c b/ipc/shm.c
index 28a444861a8f..b4073c08d0e8 100644
--- a/ipc/shm.c
+++ b/ipc/shm.c
@@ -813,23 +813,17 @@ static void shm_get_stat(struct ipc_namespace *ns, unsigned long *rss,
  * NOTE: no locks must be held, the rwsem is taken inside this function.
  */
 static int shmctl_down(struct ipc_namespace *ns, int shmid, int cmd,
-                       struct shmid_ds __user *buf, int version)
+                       struct shmid64_ds *shmid64)
 {
         struct kern_ipc_perm *ipcp;
-        struct shmid64_ds shmid64;
         struct shmid_kernel *shp;
         int err;
 
-        if (cmd == IPC_SET) {
-                if (copy_shmid_from_user(&shmid64, buf, version))
-                        return -EFAULT;
-        }
-
         down_write(&shm_ids(ns).rwsem);
         rcu_read_lock();
 
         ipcp = ipcctl_pre_down_nolock(ns, &shm_ids(ns), shmid, cmd,
-                                      &shmid64.shm_perm, 0);
+                                      &shmid64->shm_perm, 0);
         if (IS_ERR(ipcp)) {
                 err = PTR_ERR(ipcp);
                 goto out_unlock1;
@@ -849,7 +843,7 @@ static int shmctl_down(struct ipc_namespace *ns, int shmid, int cmd,
                 goto out_up;
         case IPC_SET:
                 ipc_lock_object(&shp->shm_perm);
-                err = ipc_update_perm(&shmid64.shm_perm, ipcp);
+                err = ipc_update_perm(&shmid64->shm_perm, ipcp);
                 if (err)
                         goto out_unlock0;
                 shp->shm_ctim = get_seconds();
@@ -868,212 +862,162 @@ out_up:
         return err;
 }
 
-static int shmctl_nolock(struct ipc_namespace *ns, int shmid,
-                         int cmd, int version, void __user *buf)
+static int shmctl_ipc_info(struct ipc_namespace *ns,
+                           struct shminfo64 *shminfo)
 {
-        int err;
-        struct shmid_kernel *shp;
-
-        /* preliminary security checks for *_INFO */
-        if (cmd == IPC_INFO || cmd == SHM_INFO) {
-                err = security_shm_shmctl(NULL, cmd);
-                if (err)
-                        return err;
-        }
-
-        switch (cmd) {
-        case IPC_INFO:
-        {
-                struct shminfo64 shminfo;
-
-                memset(&shminfo, 0, sizeof(shminfo));
-                shminfo.shmmni = shminfo.shmseg = ns->shm_ctlmni;
-                shminfo.shmmax = ns->shm_ctlmax;
-                shminfo.shmall = ns->shm_ctlall;
-
-                shminfo.shmmin = SHMMIN;
-                if (copy_shminfo_to_user(buf, &shminfo, version))
-                        return -EFAULT;
-
+        int err = security_shm_shmctl(NULL, IPC_INFO);
+        if (!err) {
+                memset(shminfo, 0, sizeof(*shminfo));
+                shminfo->shmmni = shminfo->shmseg = ns->shm_ctlmni;
+                shminfo->shmmax = ns->shm_ctlmax;
+                shminfo->shmall = ns->shm_ctlall;
+                shminfo->shmmin = SHMMIN;
                 down_read(&shm_ids(ns).rwsem);
                 err = ipc_get_maxid(&shm_ids(ns));
                 up_read(&shm_ids(ns).rwsem);
-
                 if (err < 0)
                         err = 0;
-                goto out;
         }
-        case SHM_INFO:
-        {
-                struct shm_info shm_info;
+        return err;
+}
 
-                memset(&shm_info, 0, sizeof(shm_info));
+static int shmctl_shm_info(struct ipc_namespace *ns,
+                           struct shm_info *shm_info)
+{
+        int err = security_shm_shmctl(NULL, SHM_INFO);
+        if (!err) {
+                memset(shm_info, 0, sizeof(*shm_info));
                 down_read(&shm_ids(ns).rwsem);
-                shm_info.used_ids = shm_ids(ns).in_use;
-                shm_get_stat(ns, &shm_info.shm_rss, &shm_info.shm_swp);
-                shm_info.shm_tot = ns->shm_tot;
-                shm_info.swap_attempts = 0;
-                shm_info.swap_successes = 0;
+                shm_info->used_ids = shm_ids(ns).in_use;
+                shm_get_stat(ns, &shm_info->shm_rss, &shm_info->shm_swp);
+                shm_info->shm_tot = ns->shm_tot;
+                shm_info->swap_attempts = 0;
+                shm_info->swap_successes = 0;
                 err = ipc_get_maxid(&shm_ids(ns));
                 up_read(&shm_ids(ns).rwsem);
-                if (copy_to_user(buf, &shm_info, sizeof(shm_info))) {
-                        err = -EFAULT;
-                        goto out;
-                }
-
-                err = err < 0 ? 0 : err;
-                goto out;
+                if (err < 0)
+                        err = 0;
         }
-        case SHM_STAT:
-        case IPC_STAT:
-        {
-                struct shmid64_ds tbuf;
-                int result;
-
-                rcu_read_lock();
-                if (cmd == SHM_STAT) {
-                        shp = shm_obtain_object(ns, shmid);
-                        if (IS_ERR(shp)) {
-                                err = PTR_ERR(shp);
-                                goto out_unlock;
-                        }
-                        result = shp->shm_perm.id;
-                } else {
-                        shp = shm_obtain_object_check(ns, shmid);
-                        if (IS_ERR(shp)) {
-                                err = PTR_ERR(shp);
-                                goto out_unlock;
-                        }
-                        result = 0;
-                }
+        return err;
+}
 
-                err = -EACCES;
-                if (ipcperms(ns, &shp->shm_perm, S_IRUGO))
-                        goto out_unlock;
+static int shmctl_stat(struct ipc_namespace *ns, int shmid,
+                        int cmd, struct shmid64_ds *tbuf)
+{
+        struct shmid_kernel *shp;
+        int result;
+        int err;
 
-                err = security_shm_shmctl(shp, cmd);
-                if (err)
+        rcu_read_lock();
+        if (cmd == SHM_STAT) {
+                shp = shm_obtain_object(ns, shmid);
+                if (IS_ERR(shp)) {
+                        err = PTR_ERR(shp);
                         goto out_unlock;
+                }
+                result = shp->shm_perm.id;
+        } else {
+                shp = shm_obtain_object_check(ns, shmid);
+                if (IS_ERR(shp)) {
+                        err = PTR_ERR(shp);
+                        goto out_unlock;
+                }
+                result = 0;
+        }
 
-                memset(&tbuf, 0, sizeof(tbuf));
-                kernel_to_ipc64_perm(&shp->shm_perm, &tbuf.shm_perm);
-                tbuf.shm_segsz  = shp->shm_segsz;
-                tbuf.shm_atime  = shp->shm_atim;
-                tbuf.shm_dtime  = shp->shm_dtim;
-                tbuf.shm_ctime  = shp->shm_ctim;
-                tbuf.shm_cpid   = shp->shm_cprid;
-                tbuf.shm_lpid   = shp->shm_lprid;
-                tbuf.shm_nattch = shp->shm_nattch;
-                rcu_read_unlock();
+        err = -EACCES;
+        if (ipcperms(ns, &shp->shm_perm, S_IRUGO))
+                goto out_unlock;
 
-                if (copy_shmid_to_user(buf, &tbuf, version))
-                        err = -EFAULT;
-                else
-                        err = result;
-                goto out;
-        }
-        default:
-                return -EINVAL;
-        }
+        err = security_shm_shmctl(shp, cmd);
+        if (err)
+                goto out_unlock;
+
+        memset(tbuf, 0, sizeof(*tbuf));
+        kernel_to_ipc64_perm(&shp->shm_perm, &tbuf->shm_perm);
+        tbuf->shm_segsz = shp->shm_segsz;
+        tbuf->shm_atime = shp->shm_atim;
+        tbuf->shm_dtime = shp->shm_dtim;
+        tbuf->shm_ctime = shp->shm_ctim;
+        tbuf->shm_cpid  = shp->shm_cprid;
+        tbuf->shm_lpid  = shp->shm_lprid;
+        tbuf->shm_nattch = shp->shm_nattch;
+        rcu_read_unlock();
+        return result;
 
 out_unlock:
         rcu_read_unlock();
-out:
         return err;
 }
 
-SYSCALL_DEFINE3(shmctl, int, shmid, int, cmd, struct shmid_ds __user *, buf)
+static int shmctl_do_lock(struct ipc_namespace *ns, int shmid, int cmd)
 {
         struct shmid_kernel *shp;
-        int err, version;
-        struct ipc_namespace *ns;
-
-        if (cmd < 0 || shmid < 0)
-                return -EINVAL;
+        struct file *shm_file;
+        int err;
 
-        version = ipc_parse_version(&cmd);
-        ns = current->nsproxy->ipc_ns;
+        rcu_read_lock();
+        shp = shm_obtain_object_check(ns, shmid);
+        if (IS_ERR(shp)) {
+                err = PTR_ERR(shp);
+                goto out_unlock1;
+        }
 
-        switch (cmd) {
-        case IPC_INFO:
-        case SHM_INFO:
-        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;
+        audit_ipc_obj(&(shp->shm_perm));
+        err = security_shm_shmctl(shp, cmd);
+        if (err)
+                goto out_unlock1;
 
-                rcu_read_lock();
-                shp = shm_obtain_object_check(ns, shmid);
-                if (IS_ERR(shp)) {
-                        err = PTR_ERR(shp);
-                        goto out_unlock1;
-                }
+        ipc_lock_object(&shp->shm_perm);
 
-                audit_ipc_obj(&(shp->shm_perm));
-                err = security_shm_shmctl(shp, cmd);
-                if (err)
-                        goto out_unlock1;
+        /* check if shm_destroy() is tearing down shp */
+        if (!ipc_valid_object(&shp->shm_perm)) {
+                err = -EIDRM;
+                goto out_unlock0;
+        }
 
-                ipc_lock_object(&shp->shm_perm);
+        if (!ns_capable(ns->user_ns, CAP_IPC_LOCK)) {
+                kuid_t euid = current_euid();
 
-                /* check if shm_destroy() is tearing down shp */
-                if (!ipc_valid_object(&shp->shm_perm)) {
-                        err = -EIDRM;
+                if (!uid_eq(euid, shp->shm_perm.uid) &&
+                    !uid_eq(euid, shp->shm_perm.cuid)) {
+                        err = -EPERM;
                         goto out_unlock0;
                 }
-
-                if (!ns_capable(ns->user_ns, CAP_IPC_LOCK)) {
-                        kuid_t euid = current_euid();
-
-                        if (!uid_eq(euid, shp->shm_perm.uid) &&
-                            !uid_eq(euid, shp->shm_perm.cuid)) {
-                                err = -EPERM;
-                                goto out_unlock0;
-                        }
-                        if (cmd == SHM_LOCK && !rlimit(RLIMIT_MEMLOCK)) {
-                                err = -EPERM;
-                                goto out_unlock0;
-                        }
+                if (cmd == SHM_LOCK && !rlimit(RLIMIT_MEMLOCK)) {
+                        err = -EPERM;
+                        goto out_unlock0;
                 }
+        }
 
-                shm_file = shp->shm_file;
-                if (is_file_hugepages(shm_file))
-                        goto out_unlock0;
+        shm_file = shp->shm_file;
+        if (is_file_hugepages(shm_file))
+                goto out_unlock0;
 
-                if (cmd == SHM_LOCK) {
-                        struct user_struct *user = current_user();
+        if (cmd == SHM_LOCK) {
+                struct user_struct *user = current_user();
 
-                        err = shmem_lock(shm_file, 1, user);
-                        if (!err && !(shp->shm_perm.mode & SHM_LOCKED)) {
-                                shp->shm_perm.mode |= SHM_LOCKED;
-                                shp->mlock_user = user;
-                        }
-                        goto out_unlock0;
+                err = shmem_lock(shm_file, 1, user);
+                if (!err && !(shp->shm_perm.mode & SHM_LOCKED)) {
+                        shp->shm_perm.mode |= SHM_LOCKED;
+                        shp->mlock_user = user;
                 }
+                goto out_unlock0;
+        }
 
-                /* SHM_UNLOCK */
-                if (!(shp->shm_perm.mode & SHM_LOCKED))
-                        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);
-                ipc_unlock_object(&shp->shm_perm);
-                rcu_read_unlock();
-                shmem_unlock_mapping(shm_file->f_mapping);
+        /* SHM_UNLOCK */
+        if (!(shp->shm_perm.mode & SHM_LOCKED))
+                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);
+        ipc_unlock_object(&shp->shm_perm);
+        rcu_read_unlock();
+        shmem_unlock_mapping(shm_file->f_mapping);
 
-                fput(shm_file);
-                return err;
-        }
-        default:
-                return -EINVAL;
-        }
+        fput(shm_file);
+        return err;
 
 out_unlock0:
         ipc_unlock_object(&shp->shm_perm);
@@ -1082,6 +1026,59 @@ out_unlock1:
         return err;
 }
 
+SYSCALL_DEFINE3(shmctl, int, shmid, int, cmd, struct shmid_ds __user *, buf)
+{
+        int err, version;
+        struct ipc_namespace *ns;
+        struct shmid64_ds tbuf;
+
+        if (cmd < 0 || shmid < 0)
+                return -EINVAL;
+
+        version = ipc_parse_version(&cmd);
+        ns = current->nsproxy->ipc_ns;
+
+        switch (cmd) {
+        case IPC_INFO: {
+                struct shminfo64 shminfo;
+                err = shmctl_ipc_info(ns, &shminfo);
+                if (err < 0)
+                        return err;
+                if (copy_shminfo_to_user(buf, &shminfo, version))
+                        err = -EFAULT;
+                return err;
+        }
+        case SHM_INFO: {
+                struct shm_info shm_info;
+                err = shmctl_shm_info(ns, &shm_info);
+                if (err < 0)
+                        return err;
+                if (copy_to_user(buf, &shm_info, sizeof(shm_info)))
+                        err = -EFAULT;
+                return err;
+        }
+        case SHM_STAT:
+        case IPC_STAT: {
+                err = shmctl_stat(ns, shmid, cmd, &tbuf);
+                if (err < 0)
+                        return err;
+                if (copy_shmid_to_user(buf, &tbuf, version))
+                        err = -EFAULT;
+                return err;
+        }
+        case IPC_SET:
+                if (copy_shmid_from_user(&tbuf, buf, version))
+                        return -EFAULT;
+        case IPC_RMID:
+                return shmctl_down(ns, shmid, cmd, &tbuf);
+        case SHM_LOCK:
+        case SHM_UNLOCK:
+                return shmctl_do_lock(ns, shmid, cmd);
+        default:
+                return -EINVAL;
+        }
+}
+
 /*
  * Fix shmaddr, allocate descriptor, map shm, add attach descriptor to lists.
  *