From c1ada3dc7219b02b3467aa906c2f5f8b098578d1 Mon Sep 17 00:00:00 2001 From: Alexey Gladkov Date: Thu, 22 Apr 2021 14:27:16 +0200 Subject: ucounts: Set ucount_max to the largest positive value the type can hold The ns->ucount_max[] is signed long which is less than the rlimit size. We have to protect ucount_max[] from overflow and only use the largest value that we can hold. On 32bit using "long" instead of "unsigned long" to hold the counts has the downside that RLIMIT_MSGQUEUE and RLIMIT_MEMLOCK are limited to 2GiB instead of 4GiB. I don't think anyone cares but it should be mentioned in case someone does. The RLIMIT_NPROC and RLIMIT_SIGPENDING used atomic_t so their maximum hasn't changed. Signed-off-by: Alexey Gladkov Link: https://lkml.kernel.org/r/1825a5dfa18bc5a570e79feb05e2bd07fd57e7e3.1619094428.git.legion@kernel.org Signed-off-by: Eric W. Biederman --- include/linux/user_namespace.h | 6 ++++++ kernel/fork.c | 8 ++++---- kernel/user_namespace.c | 8 ++++---- 3 files changed, 14 insertions(+), 8 deletions(-) diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h index 2a3177b9b8bf..61794ae32fa8 100644 --- a/include/linux/user_namespace.h +++ b/include/linux/user_namespace.h @@ -125,6 +125,12 @@ 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); 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, + enum ucount_type type, unsigned long max) +{ + ns->ucount_max[type] = max <= LONG_MAX ? max : LONG_MAX; +} + #ifdef CONFIG_USER_NS static inline struct user_namespace *get_user_ns(struct user_namespace *ns) diff --git a/kernel/fork.c b/kernel/fork.c index 610fd4de60d7..c41820481b2e 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -822,10 +822,10 @@ void __init fork_init(void) for (i = 0; i < MAX_PER_NAMESPACE_UCOUNTS; i++) init_user_ns.ucount_max[i] = max_threads/2; - init_user_ns.ucount_max[UCOUNT_RLIMIT_NPROC] = task_rlimit(&init_task, RLIMIT_NPROC); - init_user_ns.ucount_max[UCOUNT_RLIMIT_MSGQUEUE] = task_rlimit(&init_task, RLIMIT_MSGQUEUE); - init_user_ns.ucount_max[UCOUNT_RLIMIT_SIGPENDING] = task_rlimit(&init_task, RLIMIT_SIGPENDING); - init_user_ns.ucount_max[UCOUNT_RLIMIT_MEMLOCK] = task_rlimit(&init_task, RLIMIT_MEMLOCK); + set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_NPROC, task_rlimit(&init_task, RLIMIT_NPROC)); + set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_MSGQUEUE, task_rlimit(&init_task, RLIMIT_MSGQUEUE)); + set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_SIGPENDING, task_rlimit(&init_task, RLIMIT_SIGPENDING)); + set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_MEMLOCK, task_rlimit(&init_task, RLIMIT_MEMLOCK)); #ifdef CONFIG_VMAP_STACK cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "fork:vm_stack_cache", diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c index 892da1360862..d4a545bbab7f 100644 --- a/kernel/user_namespace.c +++ b/kernel/user_namespace.c @@ -122,10 +122,10 @@ int create_user_ns(struct cred *new) for (i = 0; i < MAX_PER_NAMESPACE_UCOUNTS; i++) { ns->ucount_max[i] = INT_MAX; } - ns->ucount_max[UCOUNT_RLIMIT_NPROC] = rlimit(RLIMIT_NPROC); - ns->ucount_max[UCOUNT_RLIMIT_MSGQUEUE] = rlimit(RLIMIT_MSGQUEUE); - ns->ucount_max[UCOUNT_RLIMIT_SIGPENDING] = rlimit(RLIMIT_SIGPENDING); - ns->ucount_max[UCOUNT_RLIMIT_MEMLOCK] = rlimit(RLIMIT_MEMLOCK); + 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)); ns->ucounts = ucounts; /* Inherit USERNS_SETGROUPS_ALLOWED from our parent */ -- cgit v1.2.3