proc: Usable inode numbers for the namespace file descriptors.
Assign a unique proc inode to each namespace, and use that
inode number to ensure we only allocate at most one proc
inode for every namespace in proc.
A single proc inode per namespace allows userspace to test
to see if two processes are in the same namespace.
This has been a long requested feature and only blocked because
a naive implementation would put the id in a global space and
would ultimately require having a namespace for the names of
namespaces, making migration and certain virtualization tricks
impossible.
We still don't have per superblock inode numbers for proc, which
appears necessary for application unaware checkpoint/restart and
migrations (if the application is using namespace file descriptors)
but that is now allowd by the design if it becomes important.
I have preallocated the ipc and uts initial proc inode numbers so
their structures can be statically initialized.
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
diff --git a/include/linux/ipc_namespace.h b/include/linux/ipc_namespace.h
index f03af70..fe77197 100644
--- a/include/linux/ipc_namespace.h
+++ b/include/linux/ipc_namespace.h
@@ -67,6 +67,8 @@
/* user_ns which owns the ipc ns */
struct user_namespace *user_ns;
+
+ unsigned int proc_inum;
};
extern struct ipc_namespace init_ipc_ns;
diff --git a/include/linux/pid_namespace.h b/include/linux/pid_namespace.h
index 4c96acd..bf28599 100644
--- a/include/linux/pid_namespace.h
+++ b/include/linux/pid_namespace.h
@@ -37,6 +37,7 @@
kgid_t pid_gid;
int hide_pid;
int reboot; /* group exit code if this pidns was rebooted */
+ unsigned int proc_inum;
};
extern struct pid_namespace init_pid_ns;
diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h
index bf1d000..2e24018 100644
--- a/include/linux/proc_fs.h
+++ b/include/linux/proc_fs.h
@@ -28,7 +28,11 @@
*/
enum {
- PROC_ROOT_INO = 1,
+ PROC_ROOT_INO = 1,
+ PROC_IPC_INIT_INO = 0xEFFFFFFFU,
+ PROC_UTS_INIT_INO = 0xEFFFFFFEU,
+ PROC_USER_INIT_INO = 0xEFFFFFFDU,
+ PROC_PID_INIT_INO = 0xEFFFFFFCU,
};
/*
@@ -263,6 +267,7 @@
void *(*get)(struct task_struct *task);
void (*put)(void *ns);
int (*install)(struct nsproxy *nsproxy, void *ns);
+ unsigned int (*inum)(void *ns);
};
extern const struct proc_ns_operations netns_operations;
extern const struct proc_ns_operations utsns_operations;
diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h
index 17651f0..b9bd2e6 100644
--- a/include/linux/user_namespace.h
+++ b/include/linux/user_namespace.h
@@ -25,6 +25,7 @@
struct user_namespace *parent;
kuid_t owner;
kgid_t group;
+ unsigned int proc_inum;
};
extern struct user_namespace init_user_ns;
diff --git a/include/linux/utsname.h b/include/linux/utsname.h
index 221f4a0..239e277 100644
--- a/include/linux/utsname.h
+++ b/include/linux/utsname.h
@@ -23,6 +23,7 @@
struct kref kref;
struct new_utsname name;
struct user_namespace *user_ns;
+ unsigned int proc_inum;
};
extern struct uts_namespace init_uts_ns;