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

Eric W. Biederman
2021-12-19T19:55:22Z

Alexey Gladkov <legion@kernel.org> writes:

> 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.

At a quick read through this looks good.

I will see about getting this into for-next so we can merge this for v5.17

Eric

>
> 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 */