Re: [PATCH v2 10/10] mntns: Add a limit on the number of mount namespaces.

[Serge E. Hallyn]

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

Acked-by: Serge Hallyn 

Thanks, Eric.

> ---
>  fs/namespace.c | 19 ++-
>  include/linux/user_namespace.h |  1 +
>  kernel/user_namespace.c|  1 +
>  3 files changed, 20 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/namespace.c b/fs/namespace.c
> index aabe8e397fc3..3942ae6c34f5 100644
> --- a/fs/namespace.c
> +++ b/fs/namespace.c
> @@ -2718,9 +2718,20 @@ dput_out:
>   return retval;
>  }
>  
> +static bool inc_mnt_namespaces(struct user_namespace *ns)
> +{
> + return inc_ucount(ns, UCOUNT_MNT_NAMESPACES);
> +}
> +
> +static void dec_mnt_namespaces(struct user_namespace *ns)
> +{
> + dec_ucount(ns, UCOUNT_MNT_NAMESPACES);
> +}
> +
>  static void free_mnt_ns(struct mnt_namespace *ns)
>  {
>   ns_free_inum(&ns->ns);
> + dec_mnt_namespaces(ns->user_ns);
>   put_user_ns(ns->user_ns);
>   kfree(ns);
>  }
> @@ -2739,12 +2750,18 @@ static struct mnt_namespace *alloc_mnt_ns(struct 
> user_namespace *user_ns)
>   struct mnt_namespace *new_ns;
>   int ret;
>  
> + if (!inc_mnt_namespaces(user_ns))
> + return ERR_PTR(-ENFILE);
> +
>   new_ns = kmalloc(sizeof(struct mnt_namespace), GFP_KERNEL);
> - if (!new_ns)
> + if (!new_ns) {
> + dec_mnt_namespaces(user_ns);
>   return ERR_PTR(-ENOMEM);
> + }
>   ret = ns_alloc_inum(&new_ns->ns);
>   if (ret) {
>   kfree(new_ns);
> + dec_mnt_namespaces(user_ns);
>   return ERR_PTR(ret);
>   }
>   new_ns->ns.ops = &mntns_operations;
> diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h
> index f86afa536baf..ee0e9d7b2e67 100644
> --- a/include/linux/user_namespace.h
> +++ b/include/linux/user_namespace.h
> @@ -28,6 +28,7 @@ enum ucounts {
>   UCOUNT_UTS_NAMESPACES,
>   UCOUNT_IPC_NAMESPACES,
>   UCOUNT_NET_NAMESPACES,
> + UCOUNT_MNT_NAMESPACES,
>   UCOUNT_CGROUP_NAMESPACES,
>   UCOUNT_COUNTS,
>  };
> diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
> index e326ca722ae0..f6702d84afab 100644
> --- a/kernel/user_namespace.c
> +++ b/kernel/user_namespace.c
> @@ -81,6 +81,7 @@ static struct ctl_table userns_table[] = {
>   UCOUNT_ENTRY("max_uts_namespaces"),
>   UCOUNT_ENTRY("max_ipc_namespaces"),
>   UCOUNT_ENTRY("max_net_namespaces"),
> + UCOUNT_ENTRY("max_mnt_namespaces"),
>   UCOUNT_ENTRY("max_cgroup_namespaces"),
>   { }
>  };
> -- 
> 2.8.3

[PATCH v2 10/10] mntns: Add a limit on the number of mount namespaces.

[Eric W. Biederman]

Signed-off-by: "Eric W. Biederman" 
---
 fs/namespace.c | 19 ++-
 include/linux/user_namespace.h |  1 +
 kernel/user_namespace.c|  1 +
 3 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/fs/namespace.c b/fs/namespace.c
index aabe8e397fc3..3942ae6c34f5 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -2718,9 +2718,20 @@ dput_out:
return retval;
 }
 
+static bool inc_mnt_namespaces(struct user_namespace *ns)
+{
+   return inc_ucount(ns, UCOUNT_MNT_NAMESPACES);
+}
+
+static void dec_mnt_namespaces(struct user_namespace *ns)
+{
+   dec_ucount(ns, UCOUNT_MNT_NAMESPACES);
+}
+
 static void free_mnt_ns(struct mnt_namespace *ns)
 {
ns_free_inum(&ns->ns);
+   dec_mnt_namespaces(ns->user_ns);
put_user_ns(ns->user_ns);
kfree(ns);
 }
@@ -2739,12 +2750,18 @@ static struct mnt_namespace *alloc_mnt_ns(struct 
user_namespace *user_ns)
struct mnt_namespace *new_ns;
int ret;
 
+   if (!inc_mnt_namespaces(user_ns))
+   return ERR_PTR(-ENFILE);
+
new_ns = kmalloc(sizeof(struct mnt_namespace), GFP_KERNEL);
-   if (!new_ns)
+   if (!new_ns) {
+   dec_mnt_namespaces(user_ns);
return ERR_PTR(-ENOMEM);
+   }
ret = ns_alloc_inum(&new_ns->ns);
if (ret) {
kfree(new_ns);
+   dec_mnt_namespaces(user_ns);
return ERR_PTR(ret);
}
new_ns->ns.ops = &mntns_operations;
diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h
index f86afa536baf..ee0e9d7b2e67 100644
--- a/include/linux/user_namespace.h
+++ b/include/linux/user_namespace.h
@@ -28,6 +28,7 @@ enum ucounts {
UCOUNT_UTS_NAMESPACES,
UCOUNT_IPC_NAMESPACES,
UCOUNT_NET_NAMESPACES,
+   UCOUNT_MNT_NAMESPACES,
UCOUNT_CGROUP_NAMESPACES,
UCOUNT_COUNTS,
 };
diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index e326ca722ae0..f6702d84afab 100644
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -81,6 +81,7 @@ static struct ctl_table userns_table[] = {
UCOUNT_ENTRY("max_uts_namespaces"),
UCOUNT_ENTRY("max_ipc_namespaces"),
UCOUNT_ENTRY("max_net_namespaces"),
+   UCOUNT_ENTRY("max_mnt_namespaces"),
UCOUNT_ENTRY("max_cgroup_namespaces"),
{ }
 };
-- 
2.8.3