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Subject[PATCH 7/7] uts namespaces: Implement CLONE_NEWUTS flag
Date
Implement a CLONE_NEWUTS flag, and use it at clone and sys_unshare.

Signed-off-by: Serge E. Hallyn <serue@us.ibm.com>

---

include/linux/sched.h | 1 +
include/linux/utsname.h | 7 ++++++
kernel/fork.c | 13 ++++++++++--
kernel/utsname.c | 53 +++++++++++++++++++++++++++++++++++++++++++++++
4 files changed, 72 insertions(+), 2 deletions(-)

f785920e68ae2482ff76df39d6be5335bbfcc511
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 3d74d77..7f4af71 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -62,6 +62,7 @@ #define CLONE_DETACHED 0x00400000 /* Un
#define CLONE_UNTRACED 0x00800000 /* set if the tracing process can't force CLONE_PTRACE on this clone */
#define CLONE_CHILD_SETTID 0x01000000 /* set the TID in the child */
#define CLONE_STOPPED 0x02000000 /* Start in stopped state */
+#define CLONE_NEWUTS 0x04000000 /* New utsname group? */

/*
* List of flags we want to share for kernel threads,
diff --git a/include/linux/utsname.h b/include/linux/utsname.h
index d58a406..caecec7 100644
--- a/include/linux/utsname.h
+++ b/include/linux/utsname.h
@@ -40,6 +40,8 @@ struct uts_namespace {
extern struct uts_namespace init_uts_ns;

#ifdef CONFIG_UTS_NS
+extern int unshare_utsname(unsigned long unshare_flags,
+ struct uts_namespace **new_uts);
extern int copy_utsname(int flags, struct task_struct *tsk);
extern void free_uts_ns(struct kref *kref);

@@ -70,6 +72,11 @@ static inline void put_uts_ns(struct uts
static inline void exit_utsname(struct task_struct *p)
{
}
+static inline int unshare_utsname(unsigned long unshare_flags,
+ struct uts_namespace **new_uts)
+{
+ return -EINVAL;
+}
#endif

static inline struct new_utsname *utsname(void)
diff --git a/kernel/fork.c b/kernel/fork.c
index cedfd86..c52c274 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1566,13 +1566,14 @@ asmlinkage long sys_unshare(unsigned lon
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 uts_namespace *new_uts = NULL;

check_unshare_flags(&unshare_flags);

/* Return -EINVAL for all unsupported flags */
err = -EINVAL;
if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
- CLONE_VM|CLONE_FILES|CLONE_SYSVSEM))
+ CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|CLONE_NEWUTS))
goto bad_unshare_out;

if ((err = unshare_thread(unshare_flags)))
@@ -1589,8 +1590,11 @@ asmlinkage long sys_unshare(unsigned lon
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)))
+ goto bad_unshare_cleanup_fd;

- if (new_fs || new_ns || new_sigh || new_mm || new_fd || new_ulist) {
+ if (new_fs || new_ns || new_sigh || new_mm || new_fd || new_ulist ||
+ new_uts) {

task_lock(current);

@@ -1627,6 +1631,11 @@ asmlinkage long sys_unshare(unsigned lon
new_fd = fd;
}

+ if (new_uts) {
+ put_uts_ns(current->uts_ns);
+ current->uts_ns = new_uts;
+ }
+
task_unlock(current);
}

diff --git a/kernel/utsname.c b/kernel/utsname.c
index f9e8f86..5a97a21 100644
--- a/kernel/utsname.c
+++ b/kernel/utsname.c
@@ -21,6 +21,41 @@ static inline void get_uts_ns(struct uts
}

/*
+ * Clone a new ns copying an original utsname, setting refcount to 1
+ * @old_ns: namespace to clone
+ * Return NULL on error (failure to kmalloc), new ns otherwise
+ */
+struct uts_namespace *clone_uts_ns(struct uts_namespace *old_ns)
+{
+ struct uts_namespace *ns;
+
+ ns = kmalloc(sizeof(struct uts_namespace), GFP_KERNEL);
+ if (ns) {
+ memcpy(&ns->name, &old_ns->name, sizeof(ns->name));
+ kref_init(&ns->kref);
+ }
+ return ns;
+}
+
+/*
+ * unshare the current process' utsname namespace.
+ * called only in sys_unshare()
+ */
+int unshare_utsname(unsigned long unshare_flags, struct uts_namespace **new_uts)
+{
+ if (unshare_flags & CLONE_NEWUTS) {
+ if (!capable(CAP_SYS_ADMIN))
+ return -EPERM;
+
+ *new_uts = clone_uts_ns(current->uts_ns);
+ if (!*new_uts)
+ return -ENOMEM;
+ }
+
+ return 0;
+}
+
+/*
* Copy task tsk's utsname namespace, or clone it if flags
* specifies CLONE_NEWUTS. In latter case, changes to the
* utsname of this process won't be seen by parent, and vice
@@ -29,6 +64,7 @@ static inline void get_uts_ns(struct uts
int copy_utsname(int flags, struct task_struct *tsk)
{
struct uts_namespace *old_ns = tsk->uts_ns;
+ struct uts_namespace *new_ns;
int err = 0;

if (!old_ns)
@@ -36,6 +72,23 @@ int copy_utsname(int flags, struct task_

get_uts_ns(old_ns);

+ if (!(flags & CLONE_NEWUTS))
+ return 0;
+
+ if (!capable(CAP_SYS_ADMIN)) {
+ err = -EPERM;
+ goto out;
+ }
+
+ new_ns = clone_uts_ns(old_ns);
+ if (!new_ns) {
+ err = -ENOMEM;
+ goto out;
+ }
+ tsk->uts_ns = new_ns;
+
+out:
+ put_uts_ns(old_ns);
return err;
}

--
1.3.0

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