Merge sys_clone()/sys_unshare() nsproxy and namespace handling

sys_clone() and sys_unshare() both makes copies of nsproxy and its associated
namespaces.  But they have different code paths.

This patch merges all the nsproxy and its associated namespace copy/clone
handling (as much as possible).  Posted on container list earlier for
feedback.

- Create a new nsproxy and its associated namespaces and pass it back to
  caller to attach it to right process.

- Changed all copy_*_ns() routines to return a new copy of namespace
  instead of attaching it to task->nsproxy.

- Moved the CAP_SYS_ADMIN checks out of copy_*_ns() routines.

- Removed unnessary !ns checks from copy_*_ns() and added BUG_ON()
  just incase.

- Get rid of all individual unshare_*_ns() routines and make use of
  copy_*_ns() instead.

[akpm@osdl.org: cleanups, warning fix]
[clg@fr.ibm.com: remove dup_namespaces() declaration]
[serue@us.ibm.com: fix CONFIG_IPC_NS=n, clone(CLONE_NEWIPC) retval]
[akpm@linux-foundation.org: fix build with CONFIG_SYSVIPC=n]
Signed-off-by: Badari Pulavarty <pbadari@us.ibm.com>
Signed-off-by: Serge Hallyn <serue@us.ibm.com>
Cc: Cedric Le Goater <clg@fr.ibm.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: <containers@lists.osdl.org>
Signed-off-by: Cedric Le Goater <clg@fr.ibm.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 5 insertions, 80 deletions

diff --git a/kernel/fork.c b/kernel/fork.c
index b7d169def942..fd211b9dddd4 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1516,26 +1516,6 @@ static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
 }
 
 /*
- * Unshare the mnt_namespace structure if it is being shared
- */
-static int unshare_mnt_namespace(unsigned long unshare_flags,
-		struct mnt_namespace **new_nsp, struct fs_struct *new_fs)
-{
-	struct mnt_namespace *ns = current->nsproxy->mnt_ns;
-
-	if ((unshare_flags & CLONE_NEWNS) && ns) {
-		if (!capable(CAP_SYS_ADMIN))
-			return -EPERM;
-
-		*new_nsp = dup_mnt_ns(current, new_fs ? new_fs : current->fs);
-		if (!*new_nsp)
-			return -ENOMEM;
-	}
-
-	return 0;
-}
-
-/*
  * Unsharing of sighand is not supported yet
  */
 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp)
@@ -1593,16 +1573,6 @@ static int unshare_semundo(unsigned long unshare_flags, struct sem_undo_list **n
 	return 0;
 }
 
-#ifndef CONFIG_IPC_NS
-static inline int unshare_ipcs(unsigned long flags, struct ipc_namespace **ns)
-{
-	if (flags & CLONE_NEWIPC)
-		return -EINVAL;
-
-	return 0;
-}
-#endif
-
 /*
  * unshare allows a process to 'unshare' part of the process
  * context which was originally shared using clone.  copy_*
@@ -1615,14 +1585,11 @@ asmlinkage long sys_unshare(unsigned long unshare_flags)
 {
 	int err = 0;
 	struct fs_struct *fs, *new_fs = NULL;
-	struct mnt_namespace *ns, *new_ns = NULL;
 	struct sighand_struct *new_sigh = NULL;
 	struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL;
 	struct files_struct *fd, *new_fd = NULL;
 	struct sem_undo_list *new_ulist = NULL;
 	struct nsproxy *new_nsproxy = NULL, *old_nsproxy = NULL;
-	struct uts_namespace *uts, *new_uts = NULL;
-	struct ipc_namespace *ipc, *new_ipc = NULL;
 
 	check_unshare_flags(&unshare_flags);
 
@@ -1637,36 +1604,24 @@ asmlinkage long sys_unshare(unsigned long unshare_flags)
 		goto bad_unshare_out;
 	if ((err = unshare_fs(unshare_flags, &new_fs)))
 		goto bad_unshare_cleanup_thread;
-	if ((err = unshare_mnt_namespace(unshare_flags, &new_ns, new_fs)))
-		goto bad_unshare_cleanup_fs;
 	if ((err = unshare_sighand(unshare_flags, &new_sigh)))
-		goto bad_unshare_cleanup_ns;
+		goto bad_unshare_cleanup_fs;
 	if ((err = unshare_vm(unshare_flags, &new_mm)))
 		goto bad_unshare_cleanup_sigh;
 	if ((err = unshare_fd(unshare_flags, &new_fd)))
 		goto bad_unshare_cleanup_vm;
 	if ((err = unshare_semundo(unshare_flags, &new_ulist)))
 		goto bad_unshare_cleanup_fd;
-	if ((err = unshare_utsname(unshare_flags, &new_uts)))
+	if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
+			new_fs)))
 		goto bad_unshare_cleanup_semundo;
-	if ((err = unshare_ipcs(unshare_flags, &new_ipc)))
-		goto bad_unshare_cleanup_uts;
-
-	if (new_ns || new_uts || new_ipc) {
-		old_nsproxy = current->nsproxy;
-		new_nsproxy = dup_namespaces(old_nsproxy);
-		if (!new_nsproxy) {
-			err = -ENOMEM;
-			goto bad_unshare_cleanup_ipc;
-		}
-	}
 
-	if (new_fs || new_ns || new_mm || new_fd || new_ulist ||
-				new_uts || new_ipc) {
+	if (new_fs ||  new_mm || new_fd || new_ulist || new_nsproxy) {
 
 		task_lock(current);
 
 		if (new_nsproxy) {
+			old_nsproxy = current->nsproxy;
 			current->nsproxy = new_nsproxy;
 			new_nsproxy = old_nsproxy;
 		}
@@ -1677,12 +1632,6 @@ asmlinkage long sys_unshare(unsigned long unshare_flags)
 			new_fs = fs;
 		}
 
-		if (new_ns) {
-			ns = current->nsproxy->mnt_ns;
-			current->nsproxy->mnt_ns = new_ns;
-			new_ns = ns;
-		}
-
 		if (new_mm) {
 			mm = current->mm;
 			active_mm = current->active_mm;
@@ -1698,32 +1647,12 @@ asmlinkage long sys_unshare(unsigned long unshare_flags)
 			new_fd = fd;
 		}
 
-		if (new_uts) {
-			uts = current->nsproxy->uts_ns;
-			current->nsproxy->uts_ns = new_uts;
-			new_uts = uts;
-		}
-
-		if (new_ipc) {
-			ipc = current->nsproxy->ipc_ns;
-			current->nsproxy->ipc_ns = new_ipc;
-			new_ipc = ipc;
-		}
-
 		task_unlock(current);
 	}
 
 	if (new_nsproxy)
 		put_nsproxy(new_nsproxy);
 
-bad_unshare_cleanup_ipc:
-	if (new_ipc)
-		put_ipc_ns(new_ipc);
-
-bad_unshare_cleanup_uts:
-	if (new_uts)
-		put_uts_ns(new_uts);
-
 bad_unshare_cleanup_semundo:
 bad_unshare_cleanup_fd:
 	if (new_fd)
@@ -1738,10 +1667,6 @@ bad_unshare_cleanup_sigh:
 		if (atomic_dec_and_test(&new_sigh->count))
 			kmem_cache_free(sighand_cachep, new_sigh);
 
-bad_unshare_cleanup_ns:
-	if (new_ns)
-		put_mnt_ns(new_ns);
-
 bad_unshare_cleanup_fs:
 	if (new_fs)
 		put_fs_struct(new_fs);