mirror of
https://github.com/AuxXxilium/linux_dsm_epyc7002.git
synced 2024-12-05 13:16:39 +07:00
040757f738
Always increment/decrement ucount->count under the ucounts_lock. The
increments are there already and moving the decrements there means the
locking logic of the code is simpler. This simplification in the
locking logic fixes a race between put_ucounts and get_ucounts that
could result in a use-after-free because the count could go zero then
be found by get_ucounts and then be freed by put_ucounts.
A bug presumably this one was found by a combination of syzkaller and
KASAN. JongWhan Kim reported the syzkaller failure and Dmitry Vyukov
spotted the race in the code.
Cc: stable@vger.kernel.org
Fixes: f6b2db1a3e
("userns: Make the count of user namespaces per user")
Reported-by: JongHwan Kim <zzoru007@gmail.com>
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Reviewed-by: Andrei Vagin <avagin@gmail.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
246 lines
5.7 KiB
C
246 lines
5.7 KiB
C
/*
|
|
* This program is free software; you can redistribute it and/or
|
|
* modify it under the terms of the GNU General Public License as
|
|
* published by the Free Software Foundation, version 2 of the
|
|
* License.
|
|
*/
|
|
|
|
#include <linux/stat.h>
|
|
#include <linux/sysctl.h>
|
|
#include <linux/slab.h>
|
|
#include <linux/cred.h>
|
|
#include <linux/hash.h>
|
|
#include <linux/user_namespace.h>
|
|
|
|
#define UCOUNTS_HASHTABLE_BITS 10
|
|
static struct hlist_head ucounts_hashtable[(1 << UCOUNTS_HASHTABLE_BITS)];
|
|
static DEFINE_SPINLOCK(ucounts_lock);
|
|
|
|
#define ucounts_hashfn(ns, uid) \
|
|
hash_long((unsigned long)__kuid_val(uid) + (unsigned long)(ns), \
|
|
UCOUNTS_HASHTABLE_BITS)
|
|
#define ucounts_hashentry(ns, uid) \
|
|
(ucounts_hashtable + ucounts_hashfn(ns, uid))
|
|
|
|
|
|
#ifdef CONFIG_SYSCTL
|
|
static struct ctl_table_set *
|
|
set_lookup(struct ctl_table_root *root)
|
|
{
|
|
return ¤t_user_ns()->set;
|
|
}
|
|
|
|
static int set_is_seen(struct ctl_table_set *set)
|
|
{
|
|
return ¤t_user_ns()->set == set;
|
|
}
|
|
|
|
static int set_permissions(struct ctl_table_header *head,
|
|
struct ctl_table *table)
|
|
{
|
|
struct user_namespace *user_ns =
|
|
container_of(head->set, struct user_namespace, set);
|
|
int mode;
|
|
|
|
/* Allow users with CAP_SYS_RESOURCE unrestrained access */
|
|
if (ns_capable(user_ns, CAP_SYS_RESOURCE))
|
|
mode = (table->mode & S_IRWXU) >> 6;
|
|
else
|
|
/* Allow all others at most read-only access */
|
|
mode = table->mode & S_IROTH;
|
|
return (mode << 6) | (mode << 3) | mode;
|
|
}
|
|
|
|
static struct ctl_table_root set_root = {
|
|
.lookup = set_lookup,
|
|
.permissions = set_permissions,
|
|
};
|
|
|
|
static int zero = 0;
|
|
static int int_max = INT_MAX;
|
|
#define UCOUNT_ENTRY(name) \
|
|
{ \
|
|
.procname = name, \
|
|
.maxlen = sizeof(int), \
|
|
.mode = 0644, \
|
|
.proc_handler = proc_dointvec_minmax, \
|
|
.extra1 = &zero, \
|
|
.extra2 = &int_max, \
|
|
}
|
|
static struct ctl_table user_table[] = {
|
|
UCOUNT_ENTRY("max_user_namespaces"),
|
|
UCOUNT_ENTRY("max_pid_namespaces"),
|
|
UCOUNT_ENTRY("max_uts_namespaces"),
|
|
UCOUNT_ENTRY("max_ipc_namespaces"),
|
|
UCOUNT_ENTRY("max_net_namespaces"),
|
|
UCOUNT_ENTRY("max_mnt_namespaces"),
|
|
UCOUNT_ENTRY("max_cgroup_namespaces"),
|
|
#ifdef CONFIG_INOTIFY_USER
|
|
UCOUNT_ENTRY("max_inotify_instances"),
|
|
UCOUNT_ENTRY("max_inotify_watches"),
|
|
#endif
|
|
{ }
|
|
};
|
|
#endif /* CONFIG_SYSCTL */
|
|
|
|
bool setup_userns_sysctls(struct user_namespace *ns)
|
|
{
|
|
#ifdef CONFIG_SYSCTL
|
|
struct ctl_table *tbl;
|
|
setup_sysctl_set(&ns->set, &set_root, set_is_seen);
|
|
tbl = kmemdup(user_table, sizeof(user_table), GFP_KERNEL);
|
|
if (tbl) {
|
|
int i;
|
|
for (i = 0; i < UCOUNT_COUNTS; i++) {
|
|
tbl[i].data = &ns->ucount_max[i];
|
|
}
|
|
ns->sysctls = __register_sysctl_table(&ns->set, "user", tbl);
|
|
}
|
|
if (!ns->sysctls) {
|
|
kfree(tbl);
|
|
retire_sysctl_set(&ns->set);
|
|
return false;
|
|
}
|
|
#endif
|
|
return true;
|
|
}
|
|
|
|
void retire_userns_sysctls(struct user_namespace *ns)
|
|
{
|
|
#ifdef CONFIG_SYSCTL
|
|
struct ctl_table *tbl;
|
|
|
|
tbl = ns->sysctls->ctl_table_arg;
|
|
unregister_sysctl_table(ns->sysctls);
|
|
retire_sysctl_set(&ns->set);
|
|
kfree(tbl);
|
|
#endif
|
|
}
|
|
|
|
static struct ucounts *find_ucounts(struct user_namespace *ns, kuid_t uid, struct hlist_head *hashent)
|
|
{
|
|
struct ucounts *ucounts;
|
|
|
|
hlist_for_each_entry(ucounts, hashent, node) {
|
|
if (uid_eq(ucounts->uid, uid) && (ucounts->ns == ns))
|
|
return ucounts;
|
|
}
|
|
return NULL;
|
|
}
|
|
|
|
static struct ucounts *get_ucounts(struct user_namespace *ns, kuid_t uid)
|
|
{
|
|
struct hlist_head *hashent = ucounts_hashentry(ns, uid);
|
|
struct ucounts *ucounts, *new;
|
|
|
|
spin_lock_irq(&ucounts_lock);
|
|
ucounts = find_ucounts(ns, uid, hashent);
|
|
if (!ucounts) {
|
|
spin_unlock_irq(&ucounts_lock);
|
|
|
|
new = kzalloc(sizeof(*new), GFP_KERNEL);
|
|
if (!new)
|
|
return NULL;
|
|
|
|
new->ns = ns;
|
|
new->uid = uid;
|
|
new->count = 0;
|
|
|
|
spin_lock_irq(&ucounts_lock);
|
|
ucounts = find_ucounts(ns, uid, hashent);
|
|
if (ucounts) {
|
|
kfree(new);
|
|
} else {
|
|
hlist_add_head(&new->node, hashent);
|
|
ucounts = new;
|
|
}
|
|
}
|
|
if (ucounts->count == INT_MAX)
|
|
ucounts = NULL;
|
|
else
|
|
ucounts->count += 1;
|
|
spin_unlock_irq(&ucounts_lock);
|
|
return ucounts;
|
|
}
|
|
|
|
static void put_ucounts(struct ucounts *ucounts)
|
|
{
|
|
unsigned long flags;
|
|
|
|
spin_lock_irqsave(&ucounts_lock, flags);
|
|
ucounts->count -= 1;
|
|
if (!ucounts->count)
|
|
hlist_del_init(&ucounts->node);
|
|
else
|
|
ucounts = NULL;
|
|
spin_unlock_irqrestore(&ucounts_lock, flags);
|
|
|
|
kfree(ucounts);
|
|
}
|
|
|
|
static inline bool atomic_inc_below(atomic_t *v, int u)
|
|
{
|
|
int c, old;
|
|
c = atomic_read(v);
|
|
for (;;) {
|
|
if (unlikely(c >= u))
|
|
return false;
|
|
old = atomic_cmpxchg(v, c, c+1);
|
|
if (likely(old == c))
|
|
return true;
|
|
c = old;
|
|
}
|
|
}
|
|
|
|
struct ucounts *inc_ucount(struct user_namespace *ns, kuid_t uid,
|
|
enum ucount_type type)
|
|
{
|
|
struct ucounts *ucounts, *iter, *bad;
|
|
struct user_namespace *tns;
|
|
ucounts = get_ucounts(ns, uid);
|
|
for (iter = ucounts; iter; iter = tns->ucounts) {
|
|
int max;
|
|
tns = iter->ns;
|
|
max = READ_ONCE(tns->ucount_max[type]);
|
|
if (!atomic_inc_below(&iter->ucount[type], max))
|
|
goto fail;
|
|
}
|
|
return ucounts;
|
|
fail:
|
|
bad = iter;
|
|
for (iter = ucounts; iter != bad; iter = iter->ns->ucounts)
|
|
atomic_dec(&iter->ucount[type]);
|
|
|
|
put_ucounts(ucounts);
|
|
return NULL;
|
|
}
|
|
|
|
void dec_ucount(struct ucounts *ucounts, enum ucount_type type)
|
|
{
|
|
struct ucounts *iter;
|
|
for (iter = ucounts; iter; iter = iter->ns->ucounts) {
|
|
int dec = atomic_dec_if_positive(&iter->ucount[type]);
|
|
WARN_ON_ONCE(dec < 0);
|
|
}
|
|
put_ucounts(ucounts);
|
|
}
|
|
|
|
static __init int user_namespace_sysctl_init(void)
|
|
{
|
|
#ifdef CONFIG_SYSCTL
|
|
static struct ctl_table_header *user_header;
|
|
static struct ctl_table empty[1];
|
|
/*
|
|
* It is necessary to register the user directory in the
|
|
* default set so that registrations in the child sets work
|
|
* properly.
|
|
*/
|
|
user_header = register_sysctl("user", empty);
|
|
kmemleak_ignore(user_header);
|
|
BUG_ON(!user_header);
|
|
BUG_ON(!setup_userns_sysctls(&init_user_ns));
|
|
#endif
|
|
return 0;
|
|
}
|
|
subsys_initcall(user_namespace_sysctl_init);
|