userns: Generalize the user namespace count into ucount

The same kind of recursive sane default limit and policy
countrol that has been implemented for the user namespace
is desirable for the other namespaces, so generalize
the user namespace refernce count into a ucount.

Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

1 files changed, 21 insertions, 18 deletions

diff --git a/kernel/ucount.c b/kernel/ucount.c
index 33c4187..0f9ab3b 100644
--- a/kernel/ucount.c
+++ b/kernel/ucount.c
@@ -57,16 +57,17 @@ static struct ctl_table_root set_root = {
 
 static int zero = 0;
 static int int_max = INT_MAX;
+#define UCOUNT_ENTRY(name) 				\
+	{						\
+		.procname	= name,			\
+		.maxlen		= sizeof(int),		\
+		.mode		= 0644,			\
+		.proc_handler	= proc_dointvec_minmax,	\
+		.extra1		= &zero,		\
+		.extra2		= &int_max,		\
+	}
 static struct ctl_table user_table[] = {
-	{
-		.procname	= "max_user_namespaces",
-		.data		= &init_user_ns.max_user_namespaces,
-		.maxlen		= sizeof(init_user_ns.max_user_namespaces),
-		.mode		= 0644,
-		.proc_handler	= proc_dointvec_minmax,
-		.extra1		= &zero,
-		.extra2		= &int_max,
-	},
+	UCOUNT_ENTRY("max_user_namespaces"),
 	{ }
 };
 #endif /* CONFIG_SYSCTL */
@@ -78,8 +79,10 @@ bool setup_userns_sysctls(struct user_namespace *ns)
 	setup_sysctl_set(&ns->set, &set_root, set_is_seen);
 	tbl = kmemdup(user_table, sizeof(user_table), GFP_KERNEL);
 	if (tbl) {
-		tbl[0].data = &ns->max_user_namespaces;
-
+		int i;
+		for (i = 0; i < UCOUNT_COUNTS; i++) {
+			tbl[i].data = &ns->ucount_max[i];
+		}
 		ns->sysctls = __register_sysctl_table(&ns->set, "user", tbl);
 	}
 	if (!ns->sysctls) {
@@ -172,7 +175,8 @@ static inline bool atomic_inc_below(atomic_t *v, int u)
 	}
 }
 
-struct ucounts *inc_user_namespaces(struct user_namespace *ns, kuid_t uid)
+struct ucounts *inc_ucount(struct user_namespace *ns, kuid_t uid,
+			   enum ucount_type type)
 {
 	struct ucounts *ucounts, *iter, *bad;
 	struct user_namespace *tns;
@@ -180,31 +184,30 @@ struct ucounts *inc_user_namespaces(struct user_namespace *ns, kuid_t uid)
 	for (iter = ucounts; iter; iter = tns->ucounts) {
 		int max;
 		tns = iter->ns;
-		max = READ_ONCE(tns->max_user_namespaces);
-		if (!atomic_inc_below(&iter->user_namespaces, max))
+		max = READ_ONCE(tns->ucount_max[type]);
+		if (!atomic_inc_below(&iter->ucount[type], max))
 			goto fail;
 	}
 	return ucounts;
 fail:
 	bad = iter;
 	for (iter = ucounts; iter != bad; iter = iter->ns->ucounts)
-		atomic_dec(&iter->user_namespaces);
+		atomic_dec(&iter->ucount[type]);
 
 	put_ucounts(ucounts);
 	return NULL;
 }
 
-void dec_user_namespaces(struct ucounts *ucounts)
+void dec_ucount(struct ucounts *ucounts, enum ucount_type type)
 {
 	struct ucounts *iter;
 	for (iter = ucounts; iter; iter = iter->ns->ucounts) {
-		int dec = atomic_dec_if_positive(&iter->user_namespaces);
+		int dec = atomic_dec_if_positive(&iter->ucount[type]);
 		WARN_ON_ONCE(dec < 0);
 	}
 	put_ucounts(ucounts);
 }
 
-
 static __init int user_namespace_sysctl_init(void)
 {
 #ifdef CONFIG_SYSCTL