1 // SPDX-License-Identifier: GPL-2.0-only
3 #include <linux/stat.h>
4 #include <linux/sysctl.h>
5 #include <linux/slab.h>
6 #include <linux/cred.h>
7 #include <linux/hash.h>
8 #include <linux/kmemleak.h>
9 #include <linux/user_namespace.h>
11 struct ucounts init_ucounts
= {
13 .uid
= GLOBAL_ROOT_UID
,
14 .count
= ATOMIC_INIT(1),
17 #define UCOUNTS_HASHTABLE_BITS 10
18 static struct hlist_head ucounts_hashtable
[(1 << UCOUNTS_HASHTABLE_BITS
)];
19 static DEFINE_SPINLOCK(ucounts_lock
);
21 #define ucounts_hashfn(ns, uid) \
22 hash_long((unsigned long)__kuid_val(uid) + (unsigned long)(ns), \
23 UCOUNTS_HASHTABLE_BITS)
24 #define ucounts_hashentry(ns, uid) \
25 (ucounts_hashtable + ucounts_hashfn(ns, uid))
29 static struct ctl_table_set
*
30 set_lookup(struct ctl_table_root
*root
)
32 return ¤t_user_ns()->set
;
35 static int set_is_seen(struct ctl_table_set
*set
)
37 return ¤t_user_ns()->set
== set
;
40 static int set_permissions(struct ctl_table_header
*head
,
41 struct ctl_table
*table
)
43 struct user_namespace
*user_ns
=
44 container_of(head
->set
, struct user_namespace
, set
);
47 /* Allow users with CAP_SYS_RESOURCE unrestrained access */
48 if (ns_capable(user_ns
, CAP_SYS_RESOURCE
))
49 mode
= (table
->mode
& S_IRWXU
) >> 6;
51 /* Allow all others at most read-only access */
52 mode
= table
->mode
& S_IROTH
;
53 return (mode
<< 6) | (mode
<< 3) | mode
;
56 static struct ctl_table_root set_root
= {
58 .permissions
= set_permissions
,
61 static long ue_zero
= 0;
62 static long ue_int_max
= INT_MAX
;
64 #define UCOUNT_ENTRY(name) \
67 .maxlen = sizeof(long), \
69 .proc_handler = proc_doulongvec_minmax, \
71 .extra2 = &ue_int_max, \
73 static struct ctl_table user_table
[] = {
74 UCOUNT_ENTRY("max_user_namespaces"),
75 UCOUNT_ENTRY("max_pid_namespaces"),
76 UCOUNT_ENTRY("max_uts_namespaces"),
77 UCOUNT_ENTRY("max_ipc_namespaces"),
78 UCOUNT_ENTRY("max_net_namespaces"),
79 UCOUNT_ENTRY("max_mnt_namespaces"),
80 UCOUNT_ENTRY("max_cgroup_namespaces"),
81 UCOUNT_ENTRY("max_time_namespaces"),
82 #ifdef CONFIG_INOTIFY_USER
83 UCOUNT_ENTRY("max_inotify_instances"),
84 UCOUNT_ENTRY("max_inotify_watches"),
86 #ifdef CONFIG_FANOTIFY
87 UCOUNT_ENTRY("max_fanotify_groups"),
88 UCOUNT_ENTRY("max_fanotify_marks"),
96 #endif /* CONFIG_SYSCTL */
98 bool setup_userns_sysctls(struct user_namespace
*ns
)
101 struct ctl_table
*tbl
;
103 BUILD_BUG_ON(ARRAY_SIZE(user_table
) != UCOUNT_COUNTS
+ 1);
104 setup_sysctl_set(&ns
->set
, &set_root
, set_is_seen
);
105 tbl
= kmemdup(user_table
, sizeof(user_table
), GFP_KERNEL
);
108 for (i
= 0; i
< UCOUNT_COUNTS
; i
++) {
109 tbl
[i
].data
= &ns
->ucount_max
[i
];
111 ns
->sysctls
= __register_sysctl_table(&ns
->set
, "user", tbl
);
115 retire_sysctl_set(&ns
->set
);
122 void retire_userns_sysctls(struct user_namespace
*ns
)
125 struct ctl_table
*tbl
;
127 tbl
= ns
->sysctls
->ctl_table_arg
;
128 unregister_sysctl_table(ns
->sysctls
);
129 retire_sysctl_set(&ns
->set
);
134 static struct ucounts
*find_ucounts(struct user_namespace
*ns
, kuid_t uid
, struct hlist_head
*hashent
)
136 struct ucounts
*ucounts
;
138 hlist_for_each_entry(ucounts
, hashent
, node
) {
139 if (uid_eq(ucounts
->uid
, uid
) && (ucounts
->ns
== ns
))
145 static void hlist_add_ucounts(struct ucounts
*ucounts
)
147 struct hlist_head
*hashent
= ucounts_hashentry(ucounts
->ns
, ucounts
->uid
);
148 spin_lock_irq(&ucounts_lock
);
149 hlist_add_head(&ucounts
->node
, hashent
);
150 spin_unlock_irq(&ucounts_lock
);
153 struct ucounts
*get_ucounts(struct ucounts
*ucounts
)
155 if (ucounts
&& atomic_add_negative(1, &ucounts
->count
)) {
156 put_ucounts(ucounts
);
162 struct ucounts
*alloc_ucounts(struct user_namespace
*ns
, kuid_t uid
)
164 struct hlist_head
*hashent
= ucounts_hashentry(ns
, uid
);
165 struct ucounts
*ucounts
, *new;
168 spin_lock_irq(&ucounts_lock
);
169 ucounts
= find_ucounts(ns
, uid
, hashent
);
171 spin_unlock_irq(&ucounts_lock
);
173 new = kzalloc(sizeof(*new), GFP_KERNEL
);
179 atomic_set(&new->count
, 1);
181 spin_lock_irq(&ucounts_lock
);
182 ucounts
= find_ucounts(ns
, uid
, hashent
);
186 hlist_add_head(&new->node
, hashent
);
187 get_user_ns(new->ns
);
188 spin_unlock_irq(&ucounts_lock
);
192 overflow
= atomic_add_negative(1, &ucounts
->count
);
193 spin_unlock_irq(&ucounts_lock
);
195 put_ucounts(ucounts
);
201 void put_ucounts(struct ucounts
*ucounts
)
205 if (atomic_dec_and_lock_irqsave(&ucounts
->count
, &ucounts_lock
, flags
)) {
206 hlist_del_init(&ucounts
->node
);
207 spin_unlock_irqrestore(&ucounts_lock
, flags
);
208 put_user_ns(ucounts
->ns
);
213 static inline bool atomic_long_inc_below(atomic_long_t
*v
, int u
)
216 c
= atomic_long_read(v
);
218 if (unlikely(c
>= u
))
220 old
= atomic_long_cmpxchg(v
, c
, c
+1);
221 if (likely(old
== c
))
227 struct ucounts
*inc_ucount(struct user_namespace
*ns
, kuid_t uid
,
228 enum ucount_type type
)
230 struct ucounts
*ucounts
, *iter
, *bad
;
231 struct user_namespace
*tns
;
232 ucounts
= alloc_ucounts(ns
, uid
);
233 for (iter
= ucounts
; iter
; iter
= tns
->ucounts
) {
236 max
= READ_ONCE(tns
->ucount_max
[type
]);
237 if (!atomic_long_inc_below(&iter
->ucount
[type
], max
))
243 for (iter
= ucounts
; iter
!= bad
; iter
= iter
->ns
->ucounts
)
244 atomic_long_dec(&iter
->ucount
[type
]);
246 put_ucounts(ucounts
);
250 void dec_ucount(struct ucounts
*ucounts
, enum ucount_type type
)
252 struct ucounts
*iter
;
253 for (iter
= ucounts
; iter
; iter
= iter
->ns
->ucounts
) {
254 long dec
= atomic_long_dec_if_positive(&iter
->ucount
[type
]);
255 WARN_ON_ONCE(dec
< 0);
257 put_ucounts(ucounts
);
260 long inc_rlimit_ucounts(struct ucounts
*ucounts
, enum ucount_type type
, long v
)
262 struct ucounts
*iter
;
266 for (iter
= ucounts
; iter
; iter
= iter
->ns
->ucounts
) {
267 long new = atomic_long_add_return(v
, &iter
->ucount
[type
]);
268 if (new < 0 || new > max
)
270 else if (iter
== ucounts
)
272 max
= READ_ONCE(iter
->ns
->ucount_max
[type
]);
277 bool dec_rlimit_ucounts(struct ucounts
*ucounts
, enum ucount_type type
, long v
)
279 struct ucounts
*iter
;
280 long new = -1; /* Silence compiler warning */
281 for (iter
= ucounts
; iter
; iter
= iter
->ns
->ucounts
) {
282 long dec
= atomic_long_add_return(-v
, &iter
->ucount
[type
]);
283 WARN_ON_ONCE(dec
< 0);
290 static void do_dec_rlimit_put_ucounts(struct ucounts
*ucounts
,
291 struct ucounts
*last
, enum ucount_type type
)
293 struct ucounts
*iter
, *next
;
294 for (iter
= ucounts
; iter
!= last
; iter
= next
) {
295 long dec
= atomic_long_add_return(-1, &iter
->ucount
[type
]);
296 WARN_ON_ONCE(dec
< 0);
297 next
= iter
->ns
->ucounts
;
303 void dec_rlimit_put_ucounts(struct ucounts
*ucounts
, enum ucount_type type
)
305 do_dec_rlimit_put_ucounts(ucounts
, NULL
, type
);
308 long inc_rlimit_get_ucounts(struct ucounts
*ucounts
, enum ucount_type type
)
310 /* Caller must hold a reference to ucounts */
311 struct ucounts
*iter
;
315 for (iter
= ucounts
; iter
; iter
= iter
->ns
->ucounts
) {
316 long new = atomic_long_add_return(1, &iter
->ucount
[type
]);
317 if (new < 0 || new > max
)
321 max
= READ_ONCE(iter
->ns
->ucount_max
[type
]);
323 * Grab an extra ucount reference for the caller when
324 * the rlimit count was previously 0.
328 if (!get_ucounts(iter
))
333 dec
= atomic_long_add_return(-1, &iter
->ucount
[type
]);
334 WARN_ON_ONCE(dec
< 0);
336 do_dec_rlimit_put_ucounts(ucounts
, iter
, type
);
340 bool is_ucounts_overlimit(struct ucounts
*ucounts
, enum ucount_type type
, unsigned long rlimit
)
342 struct ucounts
*iter
;
344 if (rlimit
> LONG_MAX
)
346 for (iter
= ucounts
; iter
; iter
= iter
->ns
->ucounts
) {
347 long val
= get_ucounts_value(iter
, type
);
348 if (val
< 0 || val
> max
)
350 max
= READ_ONCE(iter
->ns
->ucount_max
[type
]);
355 static __init
int user_namespace_sysctl_init(void)
358 static struct ctl_table_header
*user_header
;
359 static struct ctl_table empty
[1];
361 * It is necessary to register the user directory in the
362 * default set so that registrations in the child sets work
365 user_header
= register_sysctl("user", empty
);
366 kmemleak_ignore(user_header
);
367 BUG_ON(!user_header
);
368 BUG_ON(!setup_userns_sysctls(&init_user_ns
));
370 hlist_add_ucounts(&init_ucounts
);
371 inc_rlimit_ucounts(&init_ucounts
, UCOUNT_RLIMIT_NPROC
, 1);
374 subsys_initcall(user_namespace_sysctl_init
);