ipc: Use generic ns_common::count

Switch over ipc namespaces to use the newly introduced common lifetime
counter.

Currently every namespace type has its own lifetime counter which is stored
in the specific namespace struct. The lifetime counters are used
identically for all namespaces types. Namespaces may of course have
additional unrelated counters and these are not altered.

This introduces a common lifetime counter into struct ns_common. The
ns_common struct encompasses information that all namespaces share. That
should include the lifetime counter since its common for all of them.

It also allows us to unify the type of the counters across all namespaces.
Most of them use refcount_t but one uses atomic_t and at least one uses
kref. Especially the last one doesn't make much sense since it's just a
wrapper around refcount_t since 2016 and actually complicates cleanup
operations by having to use container_of() to cast the correct namespace
struct out of struct ns_common.

Having the lifetime counter for the namespaces in one place reduces
maintenance cost. Not just because after switching all namespaces over we
will have removed more code than we added but also because the logic is
more easily understandable and we indicate to the user that the basic
lifetime requirements for all namespaces are currently identical.

Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
Link: https://lore.kernel.org/r/159644978697.604812.16592754423881032385.stgit@localhost.localdomain
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

diff --git a/include/linux/ipc_namespace.h b/include/linux/ipc_namespace.h
index a06a78c67f19f8246b9769a87d2a3cc1ede2ff28..05e22770af51728b4fe4c8268615296bebfb622a 100644 (file)
--- a/include/linux/ipc_namespace.h
+++ b/include/linux/ipc_namespace.h
@@ -27,7 +27,6 @@ struct ipc_ids {
 };
 
 struct ipc_namespace {
-       refcount_t      count;
        struct ipc_ids  ids[3];
 
        int             sem_ctls[4];
@@ -128,7 +127,7 @@ extern struct ipc_namespace *copy_ipcs(unsigned long flags,
 static inline struct ipc_namespace *get_ipc_ns(struct ipc_namespace *ns)
 {
        if (ns)
-               refcount_inc(&ns->count);
+               refcount_inc(&ns->ns.count);
        return ns;
 }
 

diff --git a/ipc/msgutil.c b/ipc/msgutil.c
index 3149b4a379de681138b1e0535863a339b6960416..d0a0e877cadd5a41ed283ea3fde792ead7588124 100644 (file)
--- a/ipc/msgutil.c
+++ b/ipc/msgutil.c
@@ -26,7 +26,7 @@ DEFINE_SPINLOCK(mq_lock);
  * and not CONFIG_IPC_NS.
  */
 struct ipc_namespace init_ipc_ns = {
-       .count          = REFCOUNT_INIT(1),
+       .ns.count = REFCOUNT_INIT(1),
        .user_ns = &init_user_ns,
        .ns.inum = PROC_IPC_INIT_INO,
 #ifdef CONFIG_IPC_NS

diff --git a/ipc/namespace.c b/ipc/namespace.c
index 24e7b45320f724be853fe15be748229f7732beb3..7bd0766ddc3b13809e5ae912c49d266816475338 100644 (file)
--- a/ipc/namespace.c
+++ b/ipc/namespace.c
@@ -51,7 +51,7 @@ static struct ipc_namespace *create_ipc_ns(struct user_namespace *user_ns,
                goto fail_free;
        ns->ns.ops = &ipcns_operations;
 
-       refcount_set(&ns->count, 1);
+       refcount_set(&ns->ns.count, 1);
        ns->user_ns = get_user_ns(user_ns);
        ns->ucounts = ucounts;
 
@@ -164,7 +164,7 @@ static DECLARE_WORK(free_ipc_work, free_ipc);
  */
 void put_ipc_ns(struct ipc_namespace *ns)
 {
-       if (refcount_dec_and_lock(&ns->count, &mq_lock)) {
+       if (refcount_dec_and_lock(&ns->ns.count, &mq_lock)) {
                mq_clear_sbinfo(ns);
                spin_unlock(&mq_lock);