Re: [PATCH v2 06/10] utsns: Add a limit on the number of uts namespaces

[Serge E. Hallyn]

Quoting Eric W. Biederman (ebied...@xmission.com):
> Signed-off-by: "Eric W. Biederman" 

Acked-by: Serge Hallyn 

> ---
>  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 
>  #include 
>  
> +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);
> - if (err) {
> - kfree(ns);
> - return ERR_PTR(err);
> - }
> + if (err)
> + goto fail_free;
>  
>   ns->ns.ops = _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(_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);
>   kfree(ns);
> -- 
> 2.8.3

[PATCH v2 06/10] utsns: Add a limit on the number of uts namespaces

[Eric W. Biederman]

Signed-off-by: "Eric W. Biederman" 
---
 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 
 #include 
 
+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);
-   if (err) {
-   kfree(ns);
-   return ERR_PTR(err);
-   }
+   if (err)
+   goto fail_free;
 
ns->ns.ops = _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(_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);
kfree(ns);
-- 
2.8.3