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Commit 3ea056c5 authored by Alexey Dobriyan's avatar Alexey Dobriyan Committed by Linus Torvalds
Browse files

uts: create "struct uts_namespace" from kmem_cache 

So "struct uts_namespace" can enjoy fine-grained SLAB debugging and
usercopy protection.

I'd prefer shorter name "utsns" but there is "user_namespace" already.

Link: http://lkml.kernel.org/r/20180228215158.GA23146@avx2


Signed-off-by: default avatarAlexey Dobriyan <adobriyan@gmail.com>
Reviewed-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Serge Hallyn <serge@hallyn.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent bc4f2f54

include/linux/utsname.h

+6 −0
Original line number Diff line number Diff line
@@ -44,6 +44,8 @@ static inline void put_uts_ns(struct uts_namespace *ns) 
{

	kref_put(&ns->kref, free_uts_ns);

}



void uts_ns_init(void);

#else

static inline void get_uts_ns(struct uts_namespace *ns)

{
@@ -61,6 +63,10 @@ static inline struct uts_namespace *copy_utsname(unsigned long flags, 


	return old_ns;

}



static inline void uts_ns_init(void)

{

}

#endif



#ifdef CONFIG_PROC_SYSCTL

init/main.c

+2 −0
Original line number Diff line number Diff line
@@ -51,6 +51,7 @@ 
#include <linux/taskstats_kern.h>

#include <linux/delayacct.h>

#include <linux/unistd.h>

#include <linux/utsname.h>

#include <linux/rmap.h>

#include <linux/mempolicy.h>

#include <linux/key.h>
@@ -706,6 +707,7 @@ asmlinkage __visible void __init start_kernel(void) 
	cred_init();

	fork_init();

	proc_caches_init();

	uts_ns_init();

	buffer_init();

	key_init();

	security_init();

kernel/utsname.c

+16 −4
Original line number Diff line number Diff line
@@ -19,6 +19,8 @@ 
#include <linux/proc_ns.h>

#include <linux/sched/task.h>



static struct kmem_cache *uts_ns_cache __ro_after_init;



static struct ucounts *inc_uts_namespaces(struct user_namespace *ns)

{

	return inc_ucount(ns, current_euid(), UCOUNT_UTS_NAMESPACES);
@@ -33,7 +35,7 @@ static struct uts_namespace *create_uts_ns(void) 
{

	struct uts_namespace *uts_ns;



	uts_ns = kmalloc(sizeof(struct uts_namespace), GFP_KERNEL);

	uts_ns = kmem_cache_alloc(uts_ns_cache, GFP_KERNEL);

	if (uts_ns)

		kref_init(&uts_ns->kref);

	return uts_ns;
@@ -42,7 +44,7 @@ static struct uts_namespace *create_uts_ns(void) 
/*

 * Clone a new ns copying an original utsname, setting refcount to 1

 * @old_ns: namespace to clone

 * Return ERR_PTR(-ENOMEM) on error (failure to kmalloc), new ns otherwise

 * Return ERR_PTR(-ENOMEM) on error (failure to allocate), new ns otherwise

 */

static struct uts_namespace *clone_uts_ns(struct user_namespace *user_ns,

					  struct uts_namespace *old_ns)
@@ -75,7 +77,7 @@ static struct uts_namespace *clone_uts_ns(struct user_namespace *user_ns, 
	return ns;



fail_free:

	kfree(ns);

	kmem_cache_free(uts_ns_cache, ns);

fail_dec:

	dec_uts_namespaces(ucounts);

fail:
@@ -113,7 +115,7 @@ void free_uts_ns(struct kref *kref) 
	dec_uts_namespaces(ns->ucounts);

	put_user_ns(ns->user_ns);

	ns_free_inum(&ns->ns);

	kfree(ns);

	kmem_cache_free(uts_ns_cache, ns);

}



static inline struct uts_namespace *to_uts_ns(struct ns_common *ns)
@@ -169,3 +171,13 @@ const struct proc_ns_operations utsns_operations = { 
	.install	= utsns_install,

	.owner		= utsns_owner,

};



void __init uts_ns_init(void)

{

	uts_ns_cache = kmem_cache_create_usercopy(

			"uts_namespace", sizeof(struct uts_namespace), 0,

			SLAB_PANIC|SLAB_ACCOUNT,

			offsetof(struct uts_namespace, name),

			sizeof_field(struct uts_namespace, name),

			NULL);

}