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319 lines
7.6 KiB
319 lines
7.6 KiB
// SPDX-License-Identifier: GPL-2.0-only |
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#include <linux/stat.h> |
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#include <linux/sysctl.h> |
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#include <linux/slab.h> |
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#include <linux/cred.h> |
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#include <linux/hash.h> |
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#include <linux/kmemleak.h> |
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#include <linux/user_namespace.h> |
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struct ucounts init_ucounts = { |
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.ns = &init_user_ns, |
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.uid = GLOBAL_ROOT_UID, |
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.count = ATOMIC_INIT(1), |
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}; |
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#define UCOUNTS_HASHTABLE_BITS 10 |
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static struct hlist_head ucounts_hashtable[(1 << UCOUNTS_HASHTABLE_BITS)]; |
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static DEFINE_SPINLOCK(ucounts_lock); |
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#define ucounts_hashfn(ns, uid) \ |
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hash_long((unsigned long)__kuid_val(uid) + (unsigned long)(ns), \ |
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UCOUNTS_HASHTABLE_BITS) |
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#define ucounts_hashentry(ns, uid) \ |
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(ucounts_hashtable + ucounts_hashfn(ns, uid)) |
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#ifdef CONFIG_SYSCTL |
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static struct ctl_table_set * |
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set_lookup(struct ctl_table_root *root) |
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{ |
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return ¤t_user_ns()->set; |
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} |
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static int set_is_seen(struct ctl_table_set *set) |
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{ |
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return ¤t_user_ns()->set == set; |
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} |
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static int set_permissions(struct ctl_table_header *head, |
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struct ctl_table *table) |
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{ |
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struct user_namespace *user_ns = |
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container_of(head->set, struct user_namespace, set); |
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int mode; |
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/* Allow users with CAP_SYS_RESOURCE unrestrained access */ |
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if (ns_capable(user_ns, CAP_SYS_RESOURCE)) |
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mode = (table->mode & S_IRWXU) >> 6; |
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else |
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/* Allow all others at most read-only access */ |
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mode = table->mode & S_IROTH; |
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return (mode << 6) | (mode << 3) | mode; |
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} |
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static struct ctl_table_root set_root = { |
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.lookup = set_lookup, |
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.permissions = set_permissions, |
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}; |
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static long ue_zero = 0; |
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static long ue_int_max = INT_MAX; |
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#define UCOUNT_ENTRY(name) \ |
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{ \ |
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.procname = name, \ |
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.maxlen = sizeof(long), \ |
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.mode = 0644, \ |
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.proc_handler = proc_doulongvec_minmax, \ |
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.extra1 = &ue_zero, \ |
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.extra2 = &ue_int_max, \ |
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} |
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static struct ctl_table user_table[] = { |
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UCOUNT_ENTRY("max_user_namespaces"), |
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UCOUNT_ENTRY("max_pid_namespaces"), |
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UCOUNT_ENTRY("max_uts_namespaces"), |
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UCOUNT_ENTRY("max_ipc_namespaces"), |
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UCOUNT_ENTRY("max_net_namespaces"), |
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UCOUNT_ENTRY("max_mnt_namespaces"), |
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UCOUNT_ENTRY("max_cgroup_namespaces"), |
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UCOUNT_ENTRY("max_time_namespaces"), |
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#ifdef CONFIG_INOTIFY_USER |
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UCOUNT_ENTRY("max_inotify_instances"), |
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UCOUNT_ENTRY("max_inotify_watches"), |
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#endif |
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#ifdef CONFIG_FANOTIFY |
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UCOUNT_ENTRY("max_fanotify_groups"), |
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UCOUNT_ENTRY("max_fanotify_marks"), |
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#endif |
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{ }, |
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{ }, |
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{ }, |
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{ }, |
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{ } |
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}; |
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#endif /* CONFIG_SYSCTL */ |
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bool setup_userns_sysctls(struct user_namespace *ns) |
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{ |
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#ifdef CONFIG_SYSCTL |
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struct ctl_table *tbl; |
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BUILD_BUG_ON(ARRAY_SIZE(user_table) != UCOUNT_COUNTS + 1); |
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setup_sysctl_set(&ns->set, &set_root, set_is_seen); |
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tbl = kmemdup(user_table, sizeof(user_table), GFP_KERNEL); |
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if (tbl) { |
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int i; |
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for (i = 0; i < UCOUNT_COUNTS; i++) { |
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tbl[i].data = &ns->ucount_max[i]; |
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} |
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ns->sysctls = __register_sysctl_table(&ns->set, "user", tbl); |
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} |
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if (!ns->sysctls) { |
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kfree(tbl); |
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retire_sysctl_set(&ns->set); |
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return false; |
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} |
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#endif |
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return true; |
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} |
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void retire_userns_sysctls(struct user_namespace *ns) |
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{ |
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#ifdef CONFIG_SYSCTL |
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struct ctl_table *tbl; |
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tbl = ns->sysctls->ctl_table_arg; |
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unregister_sysctl_table(ns->sysctls); |
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retire_sysctl_set(&ns->set); |
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kfree(tbl); |
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#endif |
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} |
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static struct ucounts *find_ucounts(struct user_namespace *ns, kuid_t uid, struct hlist_head *hashent) |
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{ |
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struct ucounts *ucounts; |
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hlist_for_each_entry(ucounts, hashent, node) { |
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if (uid_eq(ucounts->uid, uid) && (ucounts->ns == ns)) |
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return ucounts; |
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} |
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return NULL; |
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} |
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static void hlist_add_ucounts(struct ucounts *ucounts) |
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{ |
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struct hlist_head *hashent = ucounts_hashentry(ucounts->ns, ucounts->uid); |
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spin_lock_irq(&ucounts_lock); |
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hlist_add_head(&ucounts->node, hashent); |
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spin_unlock_irq(&ucounts_lock); |
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} |
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struct ucounts *get_ucounts(struct ucounts *ucounts) |
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{ |
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if (ucounts && atomic_add_negative(1, &ucounts->count)) { |
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put_ucounts(ucounts); |
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ucounts = NULL; |
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} |
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return ucounts; |
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} |
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struct ucounts *alloc_ucounts(struct user_namespace *ns, kuid_t uid) |
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{ |
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struct hlist_head *hashent = ucounts_hashentry(ns, uid); |
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struct ucounts *ucounts, *new; |
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long overflow; |
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spin_lock_irq(&ucounts_lock); |
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ucounts = find_ucounts(ns, uid, hashent); |
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if (!ucounts) { |
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spin_unlock_irq(&ucounts_lock); |
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new = kzalloc(sizeof(*new), GFP_KERNEL); |
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if (!new) |
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return NULL; |
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new->ns = ns; |
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new->uid = uid; |
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atomic_set(&new->count, 1); |
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spin_lock_irq(&ucounts_lock); |
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ucounts = find_ucounts(ns, uid, hashent); |
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if (ucounts) { |
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kfree(new); |
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} else { |
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hlist_add_head(&new->node, hashent); |
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spin_unlock_irq(&ucounts_lock); |
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return new; |
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} |
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} |
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overflow = atomic_add_negative(1, &ucounts->count); |
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spin_unlock_irq(&ucounts_lock); |
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if (overflow) { |
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put_ucounts(ucounts); |
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return NULL; |
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} |
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return ucounts; |
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} |
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void put_ucounts(struct ucounts *ucounts) |
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{ |
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unsigned long flags; |
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if (atomic_dec_and_lock_irqsave(&ucounts->count, &ucounts_lock, flags)) { |
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hlist_del_init(&ucounts->node); |
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spin_unlock_irqrestore(&ucounts_lock, flags); |
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kfree(ucounts); |
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} |
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} |
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static inline bool atomic_long_inc_below(atomic_long_t *v, int u) |
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{ |
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long c, old; |
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c = atomic_long_read(v); |
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for (;;) { |
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if (unlikely(c >= u)) |
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return false; |
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old = atomic_long_cmpxchg(v, c, c+1); |
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if (likely(old == c)) |
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return true; |
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c = old; |
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} |
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} |
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struct ucounts *inc_ucount(struct user_namespace *ns, kuid_t uid, |
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enum ucount_type type) |
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{ |
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struct ucounts *ucounts, *iter, *bad; |
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struct user_namespace *tns; |
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ucounts = alloc_ucounts(ns, uid); |
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for (iter = ucounts; iter; iter = tns->ucounts) { |
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long max; |
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tns = iter->ns; |
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max = READ_ONCE(tns->ucount_max[type]); |
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if (!atomic_long_inc_below(&iter->ucount[type], max)) |
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goto fail; |
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} |
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return ucounts; |
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fail: |
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bad = iter; |
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for (iter = ucounts; iter != bad; iter = iter->ns->ucounts) |
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atomic_long_dec(&iter->ucount[type]); |
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put_ucounts(ucounts); |
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return NULL; |
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} |
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void dec_ucount(struct ucounts *ucounts, enum ucount_type type) |
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{ |
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struct ucounts *iter; |
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for (iter = ucounts; iter; iter = iter->ns->ucounts) { |
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long dec = atomic_long_dec_if_positive(&iter->ucount[type]); |
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WARN_ON_ONCE(dec < 0); |
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} |
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put_ucounts(ucounts); |
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} |
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long inc_rlimit_ucounts(struct ucounts *ucounts, enum ucount_type type, long v) |
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{ |
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struct ucounts *iter; |
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long ret = 0; |
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for (iter = ucounts; iter; iter = iter->ns->ucounts) { |
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long max = READ_ONCE(iter->ns->ucount_max[type]); |
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long new = atomic_long_add_return(v, &iter->ucount[type]); |
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if (new < 0 || new > max) |
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ret = LONG_MAX; |
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else if (iter == ucounts) |
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ret = new; |
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} |
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return ret; |
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} |
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bool dec_rlimit_ucounts(struct ucounts *ucounts, enum ucount_type type, long v) |
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{ |
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struct ucounts *iter; |
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long new = -1; /* Silence compiler warning */ |
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for (iter = ucounts; iter; iter = iter->ns->ucounts) { |
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long dec = atomic_long_add_return(-v, &iter->ucount[type]); |
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WARN_ON_ONCE(dec < 0); |
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if (iter == ucounts) |
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new = dec; |
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} |
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return (new == 0); |
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} |
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bool is_ucounts_overlimit(struct ucounts *ucounts, enum ucount_type type, unsigned long max) |
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{ |
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struct ucounts *iter; |
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if (get_ucounts_value(ucounts, type) > max) |
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return true; |
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for (iter = ucounts; iter; iter = iter->ns->ucounts) { |
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max = READ_ONCE(iter->ns->ucount_max[type]); |
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if (get_ucounts_value(iter, type) > max) |
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return true; |
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} |
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return false; |
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} |
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static __init int user_namespace_sysctl_init(void) |
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{ |
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#ifdef CONFIG_SYSCTL |
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static struct ctl_table_header *user_header; |
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static struct ctl_table empty[1]; |
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/* |
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* It is necessary to register the user directory in the |
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* default set so that registrations in the child sets work |
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* properly. |
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*/ |
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user_header = register_sysctl("user", empty); |
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kmemleak_ignore(user_header); |
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BUG_ON(!user_header); |
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BUG_ON(!setup_userns_sysctls(&init_user_ns)); |
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#endif |
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hlist_add_ucounts(&init_ucounts); |
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inc_rlimit_ucounts(&init_ucounts, UCOUNT_RLIMIT_NPROC, 1); |
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return 0; |
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} |
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subsys_initcall(user_namespace_sysctl_init);
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