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>

diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h
index 826de7a12a204f8ae7af9ca46a8025f357d5e768..9b676ead35c3a5ad818ca34fb7c45b54002afc11 100644 (file)
--- a/include/linux/user_namespace.h
+++ b/include/linux/user_namespace.h
@@ -23,6 +23,12 @@ struct uid_gid_map { /* 64 bytes -- 1 cache line */
 #define USERNS_INIT_FLAGS USERNS_SETGROUPS_ALLOWED
 
 struct ucounts;
+
+enum ucount_type {
+       UCOUNT_USER_NAMESPACES,
+       UCOUNT_COUNTS,
+};
+
 struct user_namespace {
        struct uid_gid_map      uid_map;
        struct uid_gid_map      gid_map;
@@ -46,7 +52,7 @@ struct user_namespace {
        struct ctl_table_header *sysctls;
 #endif
        struct ucounts          *ucounts;
-       int max_user_namespaces;
+       int ucount_max[UCOUNT_COUNTS];
 };
 
 struct ucounts {
@@ -54,15 +60,15 @@ struct ucounts {
        struct user_namespace *ns;
        kuid_t uid;
        atomic_t count;
-       atomic_t user_namespaces;
+       atomic_t ucount[UCOUNT_COUNTS];
 };
 
 extern struct user_namespace init_user_ns;
 
 bool setup_userns_sysctls(struct user_namespace *ns);
 void retire_userns_sysctls(struct user_namespace *ns);
-struct ucounts *inc_user_namespaces(struct user_namespace *ns, kuid_t uid);
-void dec_user_namespaces(struct ucounts *ucounts);
+struct ucounts *inc_ucount(struct user_namespace *ns, kuid_t uid, enum ucount_type type);
+void dec_ucount(struct ucounts *ucounts, enum ucount_type type);
 
 #ifdef CONFIG_USER_NS
 

diff --git a/kernel/fork.c b/kernel/fork.c
index d8cde533ace39178ed3a74c4c1adb0beaa01cd4c..3cb4853a59aa58ae7d448129b063227137e38617 100644 (file)
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -302,6 +302,7 @@ int arch_task_struct_size __read_mostly;
 
 void __init fork_init(void)
 {
+       int i;
 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
 #ifndef ARCH_MIN_TASKALIGN
 #define ARCH_MIN_TASKALIGN     L1_CACHE_BYTES
@@ -322,7 +323,9 @@ void __init fork_init(void)
        init_task.signal->rlim[RLIMIT_SIGPENDING] =
                init_task.signal->rlim[RLIMIT_NPROC];
 
-       init_user_ns.max_user_namespaces = max_threads/2;
+       for (i = 0; i < UCOUNT_COUNTS; i++) {
+               init_user_ns.ucount_max[i] = max_threads/2;
+       }
 }
 
 int __weak arch_dup_task_struct(struct task_struct *dst,

diff --git a/kernel/ucount.c b/kernel/ucount.c
index 33c418718304c6d0cb781d174cf69f592f2d54bb..0f9ab3b261854b95c34b5b4c7ecb8dad4e263c4e 100644 (file)
--- 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

diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index 58c67e5f851c6a022d4b6c01af96c458c9f985b0..0edafe305861e80aa40a0128bb91b90fde644dac 100644 (file)
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -31,6 +31,16 @@ static bool new_idmap_permitted(const struct file *file,
                                struct uid_gid_map *map);
 static void free_user_ns(struct work_struct *work);
 
+static struct ucounts *inc_user_namespaces(struct user_namespace *ns, kuid_t uid)
+{
+       return inc_ucount(ns, uid, UCOUNT_USER_NAMESPACES);
+}
+
+static void dec_user_namespaces(struct ucounts *ucounts)
+{
+       return dec_ucount(ucounts, UCOUNT_USER_NAMESPACES);
+}
+
 static void set_cred_user_ns(struct cred *cred, struct user_namespace *user_ns)
 {
        /* Start with the same capabilities as init but useless for doing
@@ -64,7 +74,7 @@ int create_user_ns(struct cred *new)
        kuid_t owner = new->euid;
        kgid_t group = new->egid;
        struct ucounts *ucounts;
-       int ret;
+       int ret, i;
 
        ret = -EUSERS;
        if (parent_ns->level > 32)
@@ -110,7 +120,9 @@ int create_user_ns(struct cred *new)
        ns->owner = owner;
        ns->group = group;
        INIT_WORK(&ns->work, free_user_ns);
-       ns->max_user_namespaces = INT_MAX;
+       for (i = 0; i < UCOUNT_COUNTS; i++) {
+               ns->ucount_max[i] = INT_MAX;
+       }
        ns->ucounts = ucounts;
 
        /* Inherit USERNS_SETGROUPS_ALLOWED from our parent */