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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>
This commit is contained in:
Kirill Tkhai 2020-08-03 13:16:27 +03:00 committed by Christian Brauner
parent 9a56493f69
commit 137ec390fa
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GPG Key ID: 91C61BC06578DCA2
3 changed files with 4 additions and 5 deletions
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3
include/linux/ipc_namespace.h
View File

@ -27,7 +27,6 @@ struct ipc_ids {
}; };
struct ipc_namespace { struct ipc_namespace {
refcount_t count;
struct ipc_ids ids[3]; struct ipc_ids ids[3];
int sem_ctls[4]; 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) static inline struct ipc_namespace *get_ipc_ns(struct ipc_namespace *ns)
{ {
if (ns) if (ns)
refcount_inc(&ns->count); refcount_inc(&ns->ns.count);
return ns; return ns;
} }

2
ipc/msgutil.c
View File

@ -26,7 +26,7 @@ DEFINE_SPINLOCK(mq_lock);
* and not CONFIG_IPC_NS. * and not CONFIG_IPC_NS.
*/ */
struct ipc_namespace init_ipc_ns = { struct ipc_namespace init_ipc_ns = {
.count = REFCOUNT_INIT(1), .ns.count = REFCOUNT_INIT(1),
.user_ns = &init_user_ns, .user_ns = &init_user_ns,
.ns.inum = PROC_IPC_INIT_INO, .ns.inum = PROC_IPC_INIT_INO,
#ifdef CONFIG_IPC_NS #ifdef CONFIG_IPC_NS

4
ipc/namespace.c
View File

@ -51,7 +51,7 @@ static struct ipc_namespace *create_ipc_ns(struct user_namespace *user_ns,
goto fail_free; goto fail_free;
ns->ns.ops = &ipcns_operations; 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->user_ns = get_user_ns(user_ns);
ns->ucounts = ucounts; ns->ucounts = ucounts;
@ -164,7 +164,7 @@ static DECLARE_WORK(free_ipc_work, free_ipc);
*/ */
void put_ipc_ns(struct ipc_namespace *ns) 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); mq_clear_sbinfo(ns);
spin_unlock(&mq_lock); spin_unlock(&mq_lock);