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Biederman" , Sasha Levin Subject: [PATCH 5.15.y 2/4] ucounts: Split rlimit and ucount values and max values Date: Tue, 10 Nov 2026 17:41:23 -0500 Message-ID: <20261110223252.3777469-2-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261110223252.3777469-1-sashal@kernel.org> References: <20261107061036-failed-5.15-b14fcabd34e0@kernel.org> <20261110223252.3777469-1-sashal@kernel.org> X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Alexey Gladkov [ Upstream commit de399236e240743ad2dd10d719c37b97ddf31996 ] 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 Signed-off-by: Alexey Gladkov Signed-off-by: Eric W. Biederman Link: https://lkml.kernel.org/r/20220518171730.l65lmnnjtnxnftpq@example.org Signed-off-by: Eric W. Biederman Stable-dep-of: b14fcabd34e0 ("ucount: take the rlimit reference before checking the limit") Signed-off-by: Sasha Levin --- 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 | 34 +++++++++++++++------------------ kernel/user_namespace.c | 10 +++++----- 7 files changed, 51 insertions(+), 46 deletions(-) diff --git a/fs/exec.c b/fs/exec.c index 5efe7ae6f9685..e573d35cb2037 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -1914,7 +1914,7 @@ 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 65f4e4df785d6..d7101eb734316 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 33a4240e6a6f1..45f09bec02c48 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 25fb13362d38c..87c08297fbee6 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -850,13 +850,13 @@ 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", @@ -2176,7 +2176,7 @@ static __latent_entropy struct task_struct *copy_process( goto bad_fork_free; 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_cleanup_count; diff --git a/kernel/sys.c b/kernel/sys.c index 3aa55bdcb7e41..89d8c850c13a1 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -489,7 +489,7 @@ static void flag_nproc_exceeded(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) current->flags |= PF_NPROC_EXCEEDED; else diff --git a/kernel/ucount.c b/kernel/ucount.c index a751fb6e94e51..2e2c9c2096781 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 */ @@ -257,29 +253,29 @@ 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; long ret = 0; for (iter = ucounts; iter; iter = iter->ns->ucounts) { - long new = atomic_long_add_return(v, &iter->ucount[type]); + long new = atomic_long_add_return(v, &iter->rlimit[type]); if (new < 0 || new > max) 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 */ for (iter = ucounts; iter; iter = iter->ns->ucounts) { - long dec = atomic_long_sub_return(v, &iter->ucount[type]); + long dec = atomic_long_sub_return(v, &iter->rlimit[type]); WARN_ON_ONCE(dec < 0); if (iter == ucounts) new = dec; @@ -288,11 +284,11 @@ 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) { - long dec = atomic_long_sub_return(1, &iter->ucount[type]); + long dec = atomic_long_sub_return(1, &iter->rlimit[type]); WARN_ON_ONCE(dec < 0); next = iter->ns->ucounts; if (dec == 0) @@ -300,12 +296,12 @@ 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; @@ -313,12 +309,12 @@ long inc_rlimit_get_ucounts(struct ucounts *ucounts, enum ucount_type type) long dec, ret = 0; for (iter = ucounts; iter; iter = iter->ns->ucounts) { - long new = atomic_long_add_return(1, &iter->ucount[type]); + long new = atomic_long_add_return(1, &iter->rlimit[type]); if (new < 0 || new > max) goto dec_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. @@ -330,23 +326,23 @@ long inc_rlimit_get_ucounts(struct ucounts *ucounts, enum ucount_type type) } return ret; dec_unwind: - dec = atomic_long_sub_return(1, &iter->ucount[type]); + dec = atomic_long_sub_return(1, &iter->rlimit[type]); WARN_ON_ONCE(dec < 0); do_dec_rlimit_put_ucounts(ucounts, iter, 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) { - long val = get_ucounts_value(iter, type); + long val = get_rlimit_value(iter, type); if (val < 0 || val > 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 5481ba44a8d68..981bb2d10d836 100644 --- a/kernel/user_namespace.c +++ b/kernel/user_namespace.c @@ -131,13 +131,13 @@ 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, enforced_nproc_rlimit()); - 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, enforced_nproc_rlimit()); + 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 */ -- 2.53.0