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utsns: Add a limit on the number of uts namespaces

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Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
This commit is contained in:
Eric W. Biederman 2016-08-08 14:11:25 -05:00
parent f333c700c6
commit f7af3d1c03
4 changed files with 32 additions and 5 deletions
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1
include/linux/user_namespace.h
View File

@ -27,6 +27,7 @@ struct ucounts;
enum ucount_type { enum ucount_type {
UCOUNT_USER_NAMESPACES, UCOUNT_USER_NAMESPACES,
UCOUNT_PID_NAMESPACES, UCOUNT_PID_NAMESPACES,
UCOUNT_UTS_NAMESPACES,
UCOUNT_COUNTS, UCOUNT_COUNTS,
}; };

1
include/linux/utsname.h
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@ -24,6 +24,7 @@ struct uts_namespace {
struct kref kref; 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 ns_common ns; struct ns_common ns;
}; };
extern struct uts_namespace init_uts_ns; extern struct uts_namespace init_uts_ns;

1
kernel/ucount.c
View File

@ -69,6 +69,7 @@ static int int_max = INT_MAX;
static struct ctl_table user_table[] = { static struct ctl_table user_table[] = {
UCOUNT_ENTRY("max_user_namespaces"), UCOUNT_ENTRY("max_user_namespaces"),
UCOUNT_ENTRY("max_pid_namespaces"), UCOUNT_ENTRY("max_pid_namespaces"),
UCOUNT_ENTRY("max_uts_namespaces"),
{ } { }
}; };
#endif /* CONFIG_SYSCTL */ #endif /* CONFIG_SYSCTL */

34
kernel/utsname.c
View File

@ -17,6 +17,16 @@
#include <linux/user_namespace.h> #include <linux/user_namespace.h>
#include <linux/proc_ns.h> #include <linux/proc_ns.h>
static struct ucounts *inc_uts_namespaces(struct user_namespace *ns)
{
return inc_ucount(ns, current_euid(), UCOUNT_UTS_NAMESPACES);
}
static void dec_uts_namespaces(struct ucounts *ucounts)
{
dec_ucount(ucounts, UCOUNT_UTS_NAMESPACES);
}
static struct uts_namespace *create_uts_ns(void) static struct uts_namespace *create_uts_ns(void)
{ {
struct uts_namespace *uts_ns; struct uts_namespace *uts_ns;
@ -36,18 +46,24 @@ static struct uts_namespace *clone_uts_ns(struct user_namespace *user_ns,
struct uts_namespace *old_ns) struct uts_namespace *old_ns)
{ {
struct uts_namespace *ns; struct uts_namespace *ns;
struct ucounts *ucounts;
int err; int err;
err = -ENFILE;
ucounts = inc_uts_namespaces(user_ns);
if (!ucounts)
goto fail;
err = -ENOMEM;
ns = create_uts_ns(); ns = create_uts_ns();
if (!ns) if (!ns)
return ERR_PTR(-ENOMEM); goto fail_dec;
err = ns_alloc_inum(&ns->ns); err = ns_alloc_inum(&ns->ns);
if (err) { if (err)
kfree(ns); goto fail_free;
return ERR_PTR(err);
}
ns->ucounts = ucounts;
ns->ns.ops = &utsns_operations; ns->ns.ops = &utsns_operations;
down_read(&uts_sem); down_read(&uts_sem);
@ -55,6 +71,13 @@ static struct uts_namespace *clone_uts_ns(struct user_namespace *user_ns,
ns->user_ns = get_user_ns(user_ns); ns->user_ns = get_user_ns(user_ns);
up_read(&uts_sem); up_read(&uts_sem);
return ns; return ns;
fail_free:
kfree(ns);
fail_dec:
dec_uts_namespaces(ucounts);
fail:
return ERR_PTR(err);
} }
/* /*
@ -85,6 +108,7 @@ void free_uts_ns(struct kref *kref)
struct uts_namespace *ns; struct uts_namespace *ns;
ns = container_of(kref, struct uts_namespace, kref); ns = container_of(kref, struct uts_namespace, kref);
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);
kfree(ns); kfree(ns);