Commit 9a56493f authored by Kirill Tkhai's avatar Kirill Tkhai Committed by Christian Brauner

uts: Use generic ns_common::count

Switch over uts 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: default avatarKirill Tkhai <ktkhai@virtuozzo.com>
Reviewed-by: default avatarKees Cook <keescook@chromium.org>
Acked-by: default avatarChristian Brauner <christian.brauner@ubuntu.com>
Link: https://lore.kernel.org/r/159644978167.604812.1773586504374412107.stgit@localhost.localdomainSigned-off-by: default avatarChristian Brauner <christian.brauner@ubuntu.com>
parent 8b8f3e66
...@@ -4,7 +4,6 @@ ...@@ -4,7 +4,6 @@
#include <linux/sched.h> #include <linux/sched.h>
#include <linux/kref.h>
#include <linux/nsproxy.h> #include <linux/nsproxy.h>
#include <linux/ns_common.h> #include <linux/ns_common.h>
#include <linux/err.h> #include <linux/err.h>
...@@ -22,7 +21,6 @@ struct user_namespace; ...@@ -22,7 +21,6 @@ struct user_namespace;
extern struct user_namespace init_user_ns; extern struct user_namespace init_user_ns;
struct uts_namespace { struct uts_namespace {
struct kref kref;
struct new_utsname name; struct new_utsname name;
struct user_namespace *user_ns; struct user_namespace *user_ns;
struct ucounts *ucounts; struct ucounts *ucounts;
...@@ -33,16 +31,17 @@ extern struct uts_namespace init_uts_ns; ...@@ -33,16 +31,17 @@ extern struct uts_namespace init_uts_ns;
#ifdef CONFIG_UTS_NS #ifdef CONFIG_UTS_NS
static inline void get_uts_ns(struct uts_namespace *ns) static inline void get_uts_ns(struct uts_namespace *ns)
{ {
kref_get(&ns->kref); refcount_inc(&ns->ns.count);
} }
extern struct uts_namespace *copy_utsname(unsigned long flags, extern struct uts_namespace *copy_utsname(unsigned long flags,
struct user_namespace *user_ns, struct uts_namespace *old_ns); struct user_namespace *user_ns, struct uts_namespace *old_ns);
extern void free_uts_ns(struct kref *kref); extern void free_uts_ns(struct uts_namespace *ns);
static inline void put_uts_ns(struct uts_namespace *ns) static inline void put_uts_ns(struct uts_namespace *ns)
{ {
kref_put(&ns->kref, free_uts_ns); if (refcount_dec_and_test(&ns->ns.count))
free_uts_ns(ns);
} }
void uts_ns_init(void); void uts_ns_init(void);
......
...@@ -25,7 +25,7 @@ int version_string(LINUX_VERSION_CODE); ...@@ -25,7 +25,7 @@ int version_string(LINUX_VERSION_CODE);
#endif #endif
struct uts_namespace init_uts_ns = { struct uts_namespace init_uts_ns = {
.kref = KREF_INIT(2), .ns.count = REFCOUNT_INIT(2),
.name = { .name = {
.sysname = UTS_SYSNAME, .sysname = UTS_SYSNAME,
.nodename = UTS_NODENAME, .nodename = UTS_NODENAME,
......
...@@ -33,7 +33,7 @@ static struct uts_namespace *create_uts_ns(void) ...@@ -33,7 +33,7 @@ static struct uts_namespace *create_uts_ns(void)
uts_ns = kmem_cache_alloc(uts_ns_cache, GFP_KERNEL); uts_ns = kmem_cache_alloc(uts_ns_cache, GFP_KERNEL);
if (uts_ns) if (uts_ns)
kref_init(&uts_ns->kref); refcount_set(&uts_ns->ns.count, 1);
return uts_ns; return uts_ns;
} }
...@@ -103,11 +103,8 @@ struct uts_namespace *copy_utsname(unsigned long flags, ...@@ -103,11 +103,8 @@ struct uts_namespace *copy_utsname(unsigned long flags,
return new_ns; return new_ns;
} }
void free_uts_ns(struct kref *kref) void free_uts_ns(struct uts_namespace *ns)
{ {
struct uts_namespace *ns;
ns = container_of(kref, struct uts_namespace, kref);
dec_uts_namespaces(ns->ucounts); dec_uts_namespaces(ns->ucounts);
put_user_ns(ns->user_ns); put_user_ns(ns->user_ns);
ns_free_inum(&ns->ns); ns_free_inum(&ns->ns);
......
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