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Subject[PATCH v2 06/10] utsns: Add a limit on the number of uts namespaces
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---
include/linux/user_namespace.h | 1 +
kernel/user_namespace.c | 1 +
kernel/utsname.c | 31 ++++++++++++++++++++++++++-----
3 files changed, 28 insertions(+), 5 deletions(-)

diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h
index 47733637741a..bed2506081fe 100644
--- a/include/linux/user_namespace.h
+++ b/include/linux/user_namespace.h
@@ -25,6 +25,7 @@ struct uid_gid_map { /* 64 bytes -- 1 cache line */
enum ucounts {
UCOUNT_USER_NAMESPACES,
UCOUNT_PID_NAMESPACES,
+ UCOUNT_UTS_NAMESPACES,
UCOUNT_COUNTS,
};

diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index 02a03ead7afc..6b205c24e888 100644
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -78,6 +78,7 @@ static int count_max = COUNT_MAX;
static struct ctl_table userns_table[] = {
UCOUNT_ENTRY("max_user_namespaces"),
UCOUNT_ENTRY("max_pid_namespaces"),
+ UCOUNT_ENTRY("max_uts_namespaces"),
{ }
};
#endif /* CONFIG_SYSCTL */
diff --git a/kernel/utsname.c b/kernel/utsname.c
index 831ea7108232..4f13c0419d64 100644
--- a/kernel/utsname.c
+++ b/kernel/utsname.c
@@ -17,6 +17,16 @@
#include <linux/user_namespace.h>
#include <linux/proc_ns.h>

+static bool inc_uts_namespaces(struct user_namespace *ns)
+{
+ return inc_ucount(ns, UCOUNT_UTS_NAMESPACES);
+}
+
+static void dec_uts_namespaces(struct user_namespace *ns)
+{
+ dec_ucount(ns, UCOUNT_UTS_NAMESPACES);
+}
+
static struct uts_namespace *create_uts_ns(void)
{
struct uts_namespace *uts_ns;
@@ -38,15 +48,18 @@ static struct uts_namespace *clone_uts_ns(struct user_namespace *user_ns,
struct uts_namespace *ns;
int err;

+ err = -ENFILE;
+ if (!inc_uts_namespaces(user_ns))
+ goto fail;
+
+ err = -ENOMEM;
ns = create_uts_ns();
if (!ns)
- return ERR_PTR(-ENOMEM);
+ goto fail_dec;

err = ns_alloc_inum(&ns->ns);
- if (err) {
- kfree(ns);
- return ERR_PTR(err);
- }
+ if (err)
+ goto fail_free;

ns->ns.ops = &utsns_operations;

@@ -55,6 +68,13 @@ static struct uts_namespace *clone_uts_ns(struct user_namespace *user_ns,
ns->user_ns = get_user_ns(user_ns);
up_read(&uts_sem);
return ns;
+
+fail_free:
+ kfree(ns);
+fail_dec:
+ dec_uts_namespaces(user_ns);
+fail:
+ return ERR_PTR(err);
}

/*
@@ -85,6 +105,7 @@ void free_uts_ns(struct kref *kref)
struct uts_namespace *ns;

ns = container_of(kref, struct uts_namespace, kref);
+ dec_uts_namespaces(ns->user_ns);
put_user_ns(ns->user_ns);
ns_free_inum(&ns->ns);
kfree(ns);
--
2.8.3
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