ucounts: Split rlimit and ucount values and max values

Since the semantics of maximum rlimit values are different, it would be
better not to mix ucount and rlimit values. This will prevent the error
of using inc_count/dec_ucount for rlimit parameters.

This patch also renames the functions to emphasize the lack of
connection between rlimit and ucount.

v3:
- Fix BUG:KASAN:use-after-free_in_dec_ucount.

v2:
- Fix the array-index-out-of-bounds that was found by the lkp project.

Reported-by: kernel test robot <oliver.sang@intel.com>
Signed-off-by: Alexey Gladkov <legion@kernel.org>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Link: https://lkml.kernel.org/r/20220518171730.l65lmnnjtnxnftpq@example.org
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>

1 files changed, 22 insertions, 13 deletions

diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h
index 33a4240e6a6f..45f09bec02c4 100644
--- a/include/linux/user_namespace.h
+++ b/include/linux/user_namespace.h
@@ -54,15 +54,17 @@ enum ucount_type {
 	UCOUNT_FANOTIFY_GROUPS,
 	UCOUNT_FANOTIFY_MARKS,
 #endif
+	UCOUNT_COUNTS,
+};
+
+enum rlimit_type {
 	UCOUNT_RLIMIT_NPROC,
 	UCOUNT_RLIMIT_MSGQUEUE,
 	UCOUNT_RLIMIT_SIGPENDING,
 	UCOUNT_RLIMIT_MEMLOCK,
-	UCOUNT_COUNTS,
+	UCOUNT_RLIMIT_COUNTS,
 };
 
-#define MAX_PER_NAMESPACE_UCOUNTS UCOUNT_RLIMIT_NPROC
-
 struct user_namespace {
 	struct uid_gid_map	uid_map;
 	struct uid_gid_map	gid_map;
@@ -99,6 +101,7 @@ struct user_namespace {
 #endif
 	struct ucounts		*ucounts;
 	long ucount_max[UCOUNT_COUNTS];
+	long rlimit_max[UCOUNT_RLIMIT_COUNTS];
 } __randomize_layout;
 
 struct ucounts {
@@ -107,6 +110,7 @@ struct ucounts {
 	kuid_t uid;
 	atomic_t count;
 	atomic_long_t ucount[UCOUNT_COUNTS];
+	atomic_long_t rlimit[UCOUNT_RLIMIT_COUNTS];
 };
 
 extern struct user_namespace init_user_ns;
@@ -120,21 +124,26 @@ struct ucounts *alloc_ucounts(struct user_namespace *ns, kuid_t uid);
 struct ucounts * __must_check get_ucounts(struct ucounts *ucounts);
 void put_ucounts(struct ucounts *ucounts);
 
-static inline long get_ucounts_value(struct ucounts *ucounts, enum ucount_type type)
+static inline long get_rlimit_value(struct ucounts *ucounts, enum rlimit_type type)
 {
-	return atomic_long_read(&ucounts->ucount[type]);
+	return atomic_long_read(&ucounts->rlimit[type]);
 }
 
-long inc_rlimit_ucounts(struct ucounts *ucounts, enum ucount_type type, long v);
-bool dec_rlimit_ucounts(struct ucounts *ucounts, enum ucount_type type, long v);
-long inc_rlimit_get_ucounts(struct ucounts *ucounts, enum ucount_type type);
-void dec_rlimit_put_ucounts(struct ucounts *ucounts, enum ucount_type type);
-bool is_ucounts_overlimit(struct ucounts *ucounts, enum ucount_type type, unsigned long max);
+long inc_rlimit_ucounts(struct ucounts *ucounts, enum rlimit_type type, long v);
+bool dec_rlimit_ucounts(struct ucounts *ucounts, enum rlimit_type type, long v);
+long inc_rlimit_get_ucounts(struct ucounts *ucounts, enum rlimit_type type);
+void dec_rlimit_put_ucounts(struct ucounts *ucounts, enum rlimit_type type);
+bool is_rlimit_overlimit(struct ucounts *ucounts, enum rlimit_type type, unsigned long max);
+
+static inline long get_userns_rlimit_max(struct user_namespace *ns, enum rlimit_type type)
+{
+	return READ_ONCE(ns->rlimit_max[type]);
+}
 
-static inline void set_rlimit_ucount_max(struct user_namespace *ns,
-		enum ucount_type type, unsigned long max)
+static inline void set_userns_rlimit_max(struct user_namespace *ns,
+		enum rlimit_type type, unsigned long max)
 {
-	ns->ucount_max[type] = max <= LONG_MAX ? max : LONG_MAX;
+	ns->rlimit_max[type] = max <= LONG_MAX ? max : LONG_MAX;
 }
 
 #ifdef CONFIG_USER_NS