[PATCH v2 2/2] ucounts: Move rlimit max values from ucounts max

Alexey Gladkov
2021-11-29T20:40:29Z

Since the semantics of maximum rlimit values are different, they need to
be separated from ucount_max. 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_max and ucount_max.

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>
---
include/linux/user_namespace.h | 17 ++++++++++++-----
kernel/fork.c | 10 +++++-----
kernel/ucount.c | 10 +++-------
kernel/user_namespace.c | 10 +++++-----
4 files changed, 25 insertions(+), 22 deletions(-)

diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h
index 33a4240e6a6f..812b6935f4a3 100644
--- a/include/linux/user_namespace.h
+++ b/include/linux/user_namespace.h
@@ -58,10 +58,11 @@ enum ucount_type {
UCOUNT_RLIMIT_MSGQUEUE,
UCOUNT_RLIMIT_SIGPENDING,
UCOUNT_RLIMIT_MEMLOCK,
- UCOUNT_COUNTS,
+ UCOUNT_ALL_COUNTS,
};

-#define MAX_PER_NAMESPACE_UCOUNTS UCOUNT_RLIMIT_NPROC
+#define UCOUNT_COUNTS UCOUNT_RLIMIT_NPROC
+#define RLIMIT_COUNTS UCOUNT_ALL_COUNTS - UCOUNT_COUNTS + 1

struct user_namespace {
struct uid_gid_map uid_map;
@@ -99,6 +100,7 @@ struct user_namespace {
#endif
struct ucounts *ucounts;
long ucount_max[UCOUNT_COUNTS];
+ long rlimit_max[RLIMIT_COUNTS];
} __randomize_layout;

struct ucounts {
@@ -106,7 +108,7 @@ struct ucounts {
struct user_namespace *ns;
kuid_t uid;
atomic_t count;
- atomic_long_t ucount[UCOUNT_COUNTS];
+ atomic_long_t ucount[UCOUNT_ALL_COUNTS];
};

extern struct user_namespace init_user_ns;
@@ -131,10 +133,15 @@ 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);

-static inline void set_rlimit_ucount_max(struct user_namespace *ns,
+static inline long get_userns_rlimit_max(struct user_namespace *ns, enum ucount_type type)
+{
+ return READ_ONCE(ns->rlimit_max[type - UCOUNT_COUNTS]);
+}
+
+static inline void set_userns_rlimit_max(struct user_namespace *ns,
enum ucount_type type, unsigned long max)
{
- ns->ucount_max[type] = max <= LONG_MAX ? max : LONG_MAX;
+ ns->rlimit_max[type - UCOUNT_COUNTS] = max <= LONG_MAX ? max : LONG_MAX;
}

#ifdef CONFIG_USER_NS
diff --git a/kernel/fork.c b/kernel/fork.c
index 3244cc56b697..365819458030 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -836,13 +836,13 @@ void __init fork_init(void)
init_task.signal->rlim[RLIMIT_SIGPENDING] =
init_task.signal->rlim[RLIMIT_NPROC];

- for (i = 0; i < MAX_PER_NAMESPACE_UCOUNTS; i++)
+ for (i = 0; i < UCOUNT_COUNTS; i++)
init_user_ns.ucount_max[i] = max_threads/2;

- set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_NPROC, RLIM_INFINITY);
- set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_MSGQUEUE, RLIM_INFINITY);
- set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_SIGPENDING, RLIM_INFINITY);
- set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_MEMLOCK, RLIM_INFINITY);
+ set_userns_rlimit_max(&init_user_ns, UCOUNT_RLIMIT_NPROC, RLIM_INFINITY);
+ set_userns_rlimit_max(&init_user_ns, UCOUNT_RLIMIT_MSGQUEUE, RLIM_INFINITY);
+ set_userns_rlimit_max(&init_user_ns, UCOUNT_RLIMIT_SIGPENDING, RLIM_INFINITY);
+ set_userns_rlimit_max(&init_user_ns, UCOUNT_RLIMIT_MEMLOCK, RLIM_INFINITY);

#ifdef CONFIG_VMAP_STACK
cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "fork:vm_stack_cache",
diff --git a/kernel/ucount.c b/kernel/ucount.c
index 7b32c356ebc5..ffffcfae8474 100644
--- a/kernel/ucount.c
+++ b/kernel/ucount.c
@@ -87,10 +87,6 @@ static struct ctl_table user_table[] = {
UCOUNT_ENTRY("max_fanotify_groups"),
UCOUNT_ENTRY("max_fanotify_marks"),
#endif
- { },
- { },
- { },
- { },
{ }
};
#endif /* CONFIG_SYSCTL */
@@ -273,7 +269,7 @@ long inc_rlimit_ucounts(struct ucounts *ucounts, enum ucount_type type, long v)
ret = LONG_MAX;
else if (iter == ucounts)
ret = new;
- max = READ_ONCE(iter->ns->ucount_max[type]);
+ max = get_userns_rlimit_max(iter->ns, type);
}
return ret;
}
@@ -322,7 +318,7 @@ long inc_rlimit_get_ucounts(struct ucounts *ucounts, enum ucount_type type)
goto unwind;
if (iter == ucounts)
ret = new;
- max = READ_ONCE(iter->ns->ucount_max[type]);
+ max = get_userns_rlimit_max(iter->ns, type);
/*
* Grab an extra ucount reference for the caller when
* the rlimit count was previously 0.
@@ -350,7 +346,7 @@ bool is_ucounts_overlimit(struct ucounts *ucounts, enum ucount_type type, unsign
for (iter = ucounts; iter; iter = iter->ns->ucounts) {
if (get_ucounts_value(iter, type) > max)
return true;
- max = READ_ONCE(iter->ns->ucount_max[type]);
+ max = get_userns_rlimit_max(iter->ns, type);
}
return false;
}
diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index 6b2e3ca7ee99..b9f6729b4e5f 100644
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -119,13 +119,13 @@ int create_user_ns(struct cred *new)
ns->owner = owner;
ns->group = group;
INIT_WORK(&ns->work, free_user_ns);
- for (i = 0; i < MAX_PER_NAMESPACE_UCOUNTS; i++) {
+ for (i = 0; i < UCOUNT_COUNTS; i++) {
ns->ucount_max[i] = INT_MAX;
}
- set_rlimit_ucount_max(ns, UCOUNT_RLIMIT_NPROC, rlimit(RLIMIT_NPROC));
- set_rlimit_ucount_max(ns, UCOUNT_RLIMIT_MSGQUEUE, rlimit(RLIMIT_MSGQUEUE));
- set_rlimit_ucount_max(ns, UCOUNT_RLIMIT_SIGPENDING, rlimit(RLIMIT_SIGPENDING));
- set_rlimit_ucount_max(ns, UCOUNT_RLIMIT_MEMLOCK, rlimit(RLIMIT_MEMLOCK));
+ set_userns_rlimit_max(ns, UCOUNT_RLIMIT_NPROC, rlimit(RLIMIT_NPROC));
+ set_userns_rlimit_max(ns, UCOUNT_RLIMIT_MSGQUEUE, rlimit(RLIMIT_MSGQUEUE));
+ set_userns_rlimit_max(ns, UCOUNT_RLIMIT_SIGPENDING, rlimit(RLIMIT_SIGPENDING));
+ set_userns_rlimit_max(ns, UCOUNT_RLIMIT_MEMLOCK, rlimit(RLIMIT_MEMLOCK));
ns->ucounts = ucounts;

/* Inherit USERNS_SETGROUPS_ALLOWED from our parent */
--
2.33.0