[PATCH -mm 4/10] unshare system call: allow unsharing of namespace
If the namespace structure is being shared, allocate a new one and
copy information from the current, shared, structure.
Changes since -v4 of this patch submitted on 12/13/05:
- none
Signed-off-by: Janak Desai <[email protected]>
---
fs/namespace.c | 56 +++++++++++++++++++++++++++++-----------------
include/linux/namespace.h | 1
kernel/fork.c | 17 +++++++++----
3 files changed, 48 insertions(+), 26 deletions(-)
diff -Naurp 2.6.15-mm3+unsh-fs/fs/namespace.c 2.6.15-mm3+unsh-ns/fs/namespace.c
--- 2.6.15-mm3+unsh-fs/fs/namespace.c 2006-01-12 00:24:06.000000000 +0000
+++ 2.6.15-mm3+unsh-ns/fs/namespace.c 2006-01-12 00:39:49.000000000 +0000
@@ -1321,27 +1321,17 @@ dput_out:
return retval;
}
-int copy_namespace(int flags, struct task_struct *tsk)
+/*
+ * Allocate a new namespace structure and populate it with contents
+ * copied from the namespace of the passed in task structure.
+ */
+struct namespace *dup_namespace(struct task_struct *tsk, struct fs_struct *fs)
{
struct namespace *namespace = tsk->namespace;
struct namespace *new_ns;
struct vfsmount *rootmnt = NULL, *pwdmnt = NULL, *altrootmnt = NULL;
- struct fs_struct *fs = tsk->fs;
struct vfsmount *p, *q;
- if (!namespace)
- return 0;
-
- get_namespace(namespace);
-
- if (!(flags & CLONE_NEWNS))
- return 0;
-
- if (!capable(CAP_SYS_ADMIN)) {
- put_namespace(namespace);
- return -EPERM;
- }
-
new_ns = kmalloc(sizeof(struct namespace), GFP_KERNEL);
if (!new_ns)
goto out;
@@ -1392,8 +1382,6 @@ int copy_namespace(int flags, struct tas
}
up_write(&namespace_sem);
- tsk->namespace = new_ns;
-
if (rootmnt)
mntput(rootmnt);
if (pwdmnt)
@@ -1401,12 +1389,40 @@ int copy_namespace(int flags, struct tas
if (altrootmnt)
mntput(altrootmnt);
- put_namespace(namespace);
- return 0;
+out:
+ return new_ns;
+}
+
+int copy_namespace(int flags, struct task_struct *tsk)
+{
+ struct namespace *namespace = tsk->namespace;
+ struct namespace *new_ns;
+ int err = 0;
+
+ if (!namespace)
+ return 0;
+
+ get_namespace(namespace);
+
+ if (!(flags & CLONE_NEWNS))
+ return 0;
+
+ if (!capable(CAP_SYS_ADMIN)) {
+ err = -EPERM;
+ goto out;
+ }
+
+ new_ns = dup_namespace(tsk, tsk->fs);
+ if (!new_ns) {
+ err = -ENOMEM;
+ goto out;
+ }
+
+ tsk->namespace = new_ns;
out:
put_namespace(namespace);
- return -ENOMEM;
+ return err;
}
asmlinkage long sys_mount(char __user * dev_name, char __user * dir_name,
diff -Naurp 2.6.15-mm3+unsh-fs/include/linux/namespace.h 2.6.15-mm3+unsh-ns/include/linux/namespace.h
--- 2.6.15-mm3+unsh-fs/include/linux/namespace.h 2006-01-12 00:25:13.000000000 +0000
+++ 2.6.15-mm3+unsh-ns/include/linux/namespace.h 2006-01-12 00:39:49.000000000 +0000
@@ -15,6 +15,7 @@ struct namespace {
extern int copy_namespace(int, struct task_struct *);
extern void __put_namespace(struct namespace *namespace);
+extern struct namespace *dup_namespace(struct task_struct *, struct fs_struct *);
static inline void put_namespace(struct namespace *namespace)
{
diff -Naurp 2.6.15-mm3+unsh-fs/kernel/fork.c 2.6.15-mm3+unsh-ns/kernel/fork.c
--- 2.6.15-mm3+unsh-fs/kernel/fork.c 2006-01-12 00:26:46.000000000 +0000
+++ 2.6.15-mm3+unsh-ns/kernel/fork.c 2006-01-12 00:39:49.000000000 +0000
@@ -1388,16 +1388,21 @@ static int unshare_fs(unsigned long unsh
}
/*
- * Unsharing of namespace for tasks created without CLONE_NEWNS is not
- * supported yet
+ * Unshare the namespace structure if it is being shared
*/
-static int unshare_namespace(unsigned long unshare_flags, struct namespace **new_nsp)
+static int unshare_namespace(unsigned long unshare_flags, struct namespace **new_nsp, struct fs_struct *new_fs)
{
struct namespace *ns = current->namespace;
if ((unshare_flags & CLONE_NEWNS) &&
- (ns && atomic_read(&ns->count) > 1))
- return -EINVAL;
+ (ns && atomic_read(&ns->count) > 1)) {
+ if (!capable(CAP_SYS_ADMIN))
+ return -EPERM;
+
+ *new_nsp = dup_namespace(current, new_fs ? new_fs : current->fs);
+ if (!*new_nsp)
+ return -ENOMEM;
+ }
return 0;
}
@@ -1482,7 +1487,7 @@ asmlinkage long sys_unshare(unsigned lon
goto bad_unshare_out;
if ((err = unshare_fs(unshare_flags, &new_fs)))
goto bad_unshare_cleanup_thread;
- if ((err = unshare_namespace(unshare_flags, &new_ns)))
+ if ((err = unshare_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;
-
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