[PATCH v3] ucounts: Split rlimit and ucount values and max values

Alexey Gladkov
2021-12-17T14:48:40Z

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.

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>
---
fs/exec.c | 2 +-
fs/proc/array.c | 2 +-
include/linux/user_namespace.h | 35 +++++++++++++++++++++-------------
kernel/fork.c | 12 ++++++------
kernel/sys.c | 2 +-
kernel/ucount.c | 24 ++++++++++-------------
kernel/user_namespace.c | 10 +++++-----
7 files changed, 46 insertions(+), 41 deletions(-)

diff --git a/fs/exec.c b/fs/exec.c
index 537d92c41105..d3f769837058 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1877,7 +1877,7 @@ static int do_execveat_common(int fd, struct filename *filename,
* whether NPROC limit is still exceeded.
*/
if ((current->flags & PF_NPROC_EXCEEDED) &&
- is_ucounts_overlimit(current_ucounts(), UCOUNT_RLIMIT_NPROC, rlimit(RLIMIT_NPROC))) {
+ is_rlimit_overlimit(current_ucounts(), UCOUNT_RLIMIT_NPROC, rlimit(RLIMIT_NPROC))) {
retval = -EAGAIN;
goto out_ret;
}
diff --git a/fs/proc/array.c b/fs/proc/array.c
index ff869a66b34e..d3fa539c755e 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -274,7 +274,7 @@ static inline void task_sig(struct seq_file *m, struct task_struct *p)
collect_sigign_sigcatch(p, &ignored, &caught);
num_threads = get_nr_threads(p);
rcu_read_lock(); /* FIXME: is this correct? */
- qsize = get_ucounts_value(task_ucounts(p), UCOUNT_RLIMIT_SIGPENDING);
+ qsize = get_rlimit_value(task_ucounts(p), UCOUNT_RLIMIT_SIGPENDING);
rcu_read_unlock();
qlim = task_rlimit(p, RLIMIT_SIGPENDING);
unlock_task_sighand(p, &flags);
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
diff --git a/kernel/fork.c b/kernel/fork.c
index 3244cc56b697..fb68d56bcd7e 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",
@@ -2053,7 +2053,7 @@ static __latent_entropy struct task_struct *copy_process(
DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
#endif
retval = -EAGAIN;
- if (is_ucounts_overlimit(task_ucounts(p), UCOUNT_RLIMIT_NPROC, rlimit(RLIMIT_NPROC))) {
+ if (is_rlimit_overlimit(task_ucounts(p), UCOUNT_RLIMIT_NPROC, rlimit(RLIMIT_NPROC))) {
if (p->real_cred->user != INIT_USER &&
!capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN))
goto bad_fork_free;
diff --git a/kernel/sys.c b/kernel/sys.c
index 8fdac0d90504..2c86d245acd6 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -479,7 +479,7 @@ static int set_user(struct cred *new)
* for programs doing set*uid()+execve() by harmlessly deferring the
* failure to the execve() stage.
*/
- if (is_ucounts_overlimit(new->ucounts, UCOUNT_RLIMIT_NPROC, rlimit(RLIMIT_NPROC)) &&
+ if (is_rlimit_overlimit(new->ucounts, UCOUNT_RLIMIT_NPROC, rlimit(RLIMIT_NPROC)) &&
new_user != INIT_USER &&
!capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN))
current->flags |= PF_NPROC_EXCEEDED;
diff --git a/kernel/ucount.c b/kernel/ucount.c
index 7b32c356ebc5..22070f004e97 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 */
@@ -261,7 +257,7 @@ void dec_ucount(struct ucounts *ucounts, enum ucount_type type)
put_ucounts(ucounts);
}

-long inc_rlimit_ucounts(struct ucounts *ucounts, enum ucount_type type, long v)
+long inc_rlimit_ucounts(struct ucounts *ucounts, enum rlimit_type type, long v)
{
struct ucounts *iter;
long max = LONG_MAX;
@@ -273,12 +269,12 @@ 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;
}

-bool dec_rlimit_ucounts(struct ucounts *ucounts, enum ucount_type type, long v)
+bool dec_rlimit_ucounts(struct ucounts *ucounts, enum rlimit_type type, long v)
{
struct ucounts *iter;
long new = -1; /* Silence compiler warning */
@@ -292,7 +288,7 @@ bool dec_rlimit_ucounts(struct ucounts *ucounts, enum ucount_type type, long v)
}

static void do_dec_rlimit_put_ucounts(struct ucounts *ucounts,
- struct ucounts *last, enum ucount_type type)
+ struct ucounts *last, enum rlimit_type type)
{
struct ucounts *iter, *next;
for (iter = ucounts; iter != last; iter = next) {
@@ -304,12 +300,12 @@ static void do_dec_rlimit_put_ucounts(struct ucounts *ucounts,
}
}

-void dec_rlimit_put_ucounts(struct ucounts *ucounts, enum ucount_type type)
+void dec_rlimit_put_ucounts(struct ucounts *ucounts, enum rlimit_type type)
{
do_dec_rlimit_put_ucounts(ucounts, NULL, type);
}

-long inc_rlimit_get_ucounts(struct ucounts *ucounts, enum ucount_type type)
+long inc_rlimit_get_ucounts(struct ucounts *ucounts, enum rlimit_type type)
{
/* Caller must hold a reference to ucounts */
struct ucounts *iter;
@@ -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.
@@ -341,16 +337,16 @@ long inc_rlimit_get_ucounts(struct ucounts *ucounts, enum ucount_type type)
return 0;
}

-bool is_ucounts_overlimit(struct ucounts *ucounts, enum ucount_type type, unsigned long rlimit)
+bool is_rlimit_overlimit(struct ucounts *ucounts, enum rlimit_type type, unsigned long rlimit)
{
struct ucounts *iter;
long max = rlimit;
if (rlimit > LONG_MAX)
max = LONG_MAX;
for (iter = ucounts; iter; iter = iter->ns->ucounts) {
- if (get_ucounts_value(iter, type) > max)
+ if (get_rlimit_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