Commit | Line | Data |
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1da177e4 LT |
1 | /* |
2 | * linux/kernel/seccomp.c | |
3 | * | |
4 | * Copyright 2004-2005 Andrea Arcangeli <andrea@cpushare.com> | |
5 | * | |
e2cfabdf WD |
6 | * Copyright (C) 2012 Google, Inc. |
7 | * Will Drewry <wad@chromium.org> | |
8 | * | |
9 | * This defines a simple but solid secure-computing facility. | |
10 | * | |
11 | * Mode 1 uses a fixed list of allowed system calls. | |
12 | * Mode 2 allows user-defined system call filters in the form | |
13 | * of Berkeley Packet Filters/Linux Socket Filters. | |
1da177e4 LT |
14 | */ |
15 | ||
0b5fa229 | 16 | #include <linux/refcount.h> |
85e7bac3 | 17 | #include <linux/audit.h> |
5b101740 | 18 | #include <linux/compat.h> |
b25e6716 | 19 | #include <linux/coredump.h> |
e2cfabdf | 20 | #include <linux/sched.h> |
68db0cf1 | 21 | #include <linux/sched/task_stack.h> |
e2cfabdf | 22 | #include <linux/seccomp.h> |
c8bee430 | 23 | #include <linux/slab.h> |
48dc92b9 | 24 | #include <linux/syscalls.h> |
1da177e4 | 25 | |
a4412fc9 | 26 | #ifdef CONFIG_HAVE_ARCH_SECCOMP_FILTER |
e2cfabdf | 27 | #include <asm/syscall.h> |
a4412fc9 | 28 | #endif |
e2cfabdf WD |
29 | |
30 | #ifdef CONFIG_SECCOMP_FILTER | |
e2cfabdf | 31 | #include <linux/filter.h> |
c2e1f2e3 | 32 | #include <linux/pid.h> |
fb0fadf9 | 33 | #include <linux/ptrace.h> |
e2cfabdf | 34 | #include <linux/security.h> |
e2cfabdf WD |
35 | #include <linux/tracehook.h> |
36 | #include <linux/uaccess.h> | |
37 | ||
38 | /** | |
39 | * struct seccomp_filter - container for seccomp BPF programs | |
40 | * | |
41 | * @usage: reference count to manage the object lifetime. | |
42 | * get/put helpers should be used when accessing an instance | |
43 | * outside of a lifetime-guarded section. In general, this | |
44 | * is only needed for handling filters shared across tasks. | |
45 | * @prev: points to a previously installed, or inherited, filter | |
285fdfc5 | 46 | * @prog: the BPF program to evaluate |
e2cfabdf WD |
47 | * |
48 | * seccomp_filter objects are organized in a tree linked via the @prev | |
49 | * pointer. For any task, it appears to be a singly-linked list starting | |
50 | * with current->seccomp.filter, the most recently attached or inherited filter. | |
51 | * However, multiple filters may share a @prev node, by way of fork(), which | |
52 | * results in a unidirectional tree existing in memory. This is similar to | |
53 | * how namespaces work. | |
54 | * | |
55 | * seccomp_filter objects should never be modified after being attached | |
56 | * to a task_struct (other than @usage). | |
57 | */ | |
58 | struct seccomp_filter { | |
0b5fa229 | 59 | refcount_t usage; |
e2cfabdf | 60 | struct seccomp_filter *prev; |
7ae457c1 | 61 | struct bpf_prog *prog; |
e2cfabdf WD |
62 | }; |
63 | ||
64 | /* Limit any path through the tree to 256KB worth of instructions. */ | |
65 | #define MAX_INSNS_PER_PATH ((1 << 18) / sizeof(struct sock_filter)) | |
66 | ||
bd4cf0ed | 67 | /* |
e2cfabdf WD |
68 | * Endianness is explicitly ignored and left for BPF program authors to manage |
69 | * as per the specific architecture. | |
70 | */ | |
bd4cf0ed | 71 | static void populate_seccomp_data(struct seccomp_data *sd) |
e2cfabdf | 72 | { |
bd4cf0ed AS |
73 | struct task_struct *task = current; |
74 | struct pt_regs *regs = task_pt_regs(task); | |
2eac7648 | 75 | unsigned long args[6]; |
e2cfabdf | 76 | |
bd4cf0ed | 77 | sd->nr = syscall_get_nr(task, regs); |
0b747172 | 78 | sd->arch = syscall_get_arch(); |
2eac7648 DB |
79 | syscall_get_arguments(task, regs, 0, 6, args); |
80 | sd->args[0] = args[0]; | |
81 | sd->args[1] = args[1]; | |
82 | sd->args[2] = args[2]; | |
83 | sd->args[3] = args[3]; | |
84 | sd->args[4] = args[4]; | |
85 | sd->args[5] = args[5]; | |
bd4cf0ed | 86 | sd->instruction_pointer = KSTK_EIP(task); |
e2cfabdf WD |
87 | } |
88 | ||
89 | /** | |
90 | * seccomp_check_filter - verify seccomp filter code | |
91 | * @filter: filter to verify | |
92 | * @flen: length of filter | |
93 | * | |
4df95ff4 | 94 | * Takes a previously checked filter (by bpf_check_classic) and |
e2cfabdf WD |
95 | * redirects all filter code that loads struct sk_buff data |
96 | * and related data through seccomp_bpf_load. It also | |
97 | * enforces length and alignment checking of those loads. | |
98 | * | |
99 | * Returns 0 if the rule set is legal or -EINVAL if not. | |
100 | */ | |
101 | static int seccomp_check_filter(struct sock_filter *filter, unsigned int flen) | |
102 | { | |
103 | int pc; | |
104 | for (pc = 0; pc < flen; pc++) { | |
105 | struct sock_filter *ftest = &filter[pc]; | |
106 | u16 code = ftest->code; | |
107 | u32 k = ftest->k; | |
108 | ||
109 | switch (code) { | |
34805931 | 110 | case BPF_LD | BPF_W | BPF_ABS: |
bd4cf0ed | 111 | ftest->code = BPF_LDX | BPF_W | BPF_ABS; |
e2cfabdf WD |
112 | /* 32-bit aligned and not out of bounds. */ |
113 | if (k >= sizeof(struct seccomp_data) || k & 3) | |
114 | return -EINVAL; | |
115 | continue; | |
34805931 | 116 | case BPF_LD | BPF_W | BPF_LEN: |
bd4cf0ed | 117 | ftest->code = BPF_LD | BPF_IMM; |
e2cfabdf WD |
118 | ftest->k = sizeof(struct seccomp_data); |
119 | continue; | |
34805931 | 120 | case BPF_LDX | BPF_W | BPF_LEN: |
bd4cf0ed | 121 | ftest->code = BPF_LDX | BPF_IMM; |
e2cfabdf WD |
122 | ftest->k = sizeof(struct seccomp_data); |
123 | continue; | |
124 | /* Explicitly include allowed calls. */ | |
34805931 DB |
125 | case BPF_RET | BPF_K: |
126 | case BPF_RET | BPF_A: | |
127 | case BPF_ALU | BPF_ADD | BPF_K: | |
128 | case BPF_ALU | BPF_ADD | BPF_X: | |
129 | case BPF_ALU | BPF_SUB | BPF_K: | |
130 | case BPF_ALU | BPF_SUB | BPF_X: | |
131 | case BPF_ALU | BPF_MUL | BPF_K: | |
132 | case BPF_ALU | BPF_MUL | BPF_X: | |
133 | case BPF_ALU | BPF_DIV | BPF_K: | |
134 | case BPF_ALU | BPF_DIV | BPF_X: | |
135 | case BPF_ALU | BPF_AND | BPF_K: | |
136 | case BPF_ALU | BPF_AND | BPF_X: | |
137 | case BPF_ALU | BPF_OR | BPF_K: | |
138 | case BPF_ALU | BPF_OR | BPF_X: | |
139 | case BPF_ALU | BPF_XOR | BPF_K: | |
140 | case BPF_ALU | BPF_XOR | BPF_X: | |
141 | case BPF_ALU | BPF_LSH | BPF_K: | |
142 | case BPF_ALU | BPF_LSH | BPF_X: | |
143 | case BPF_ALU | BPF_RSH | BPF_K: | |
144 | case BPF_ALU | BPF_RSH | BPF_X: | |
145 | case BPF_ALU | BPF_NEG: | |
146 | case BPF_LD | BPF_IMM: | |
147 | case BPF_LDX | BPF_IMM: | |
148 | case BPF_MISC | BPF_TAX: | |
149 | case BPF_MISC | BPF_TXA: | |
150 | case BPF_LD | BPF_MEM: | |
151 | case BPF_LDX | BPF_MEM: | |
152 | case BPF_ST: | |
153 | case BPF_STX: | |
154 | case BPF_JMP | BPF_JA: | |
155 | case BPF_JMP | BPF_JEQ | BPF_K: | |
156 | case BPF_JMP | BPF_JEQ | BPF_X: | |
157 | case BPF_JMP | BPF_JGE | BPF_K: | |
158 | case BPF_JMP | BPF_JGE | BPF_X: | |
159 | case BPF_JMP | BPF_JGT | BPF_K: | |
160 | case BPF_JMP | BPF_JGT | BPF_X: | |
161 | case BPF_JMP | BPF_JSET | BPF_K: | |
162 | case BPF_JMP | BPF_JSET | BPF_X: | |
e2cfabdf WD |
163 | continue; |
164 | default: | |
165 | return -EINVAL; | |
166 | } | |
167 | } | |
168 | return 0; | |
169 | } | |
170 | ||
171 | /** | |
285fdfc5 MS |
172 | * seccomp_run_filters - evaluates all seccomp filters against @sd |
173 | * @sd: optional seccomp data to be passed to filters | |
deb4de8b KC |
174 | * @match: stores struct seccomp_filter that resulted in the return value, |
175 | * unless filter returned SECCOMP_RET_ALLOW, in which case it will | |
176 | * be unchanged. | |
e2cfabdf WD |
177 | * |
178 | * Returns valid seccomp BPF response codes. | |
179 | */ | |
deb4de8b KC |
180 | static u32 seccomp_run_filters(const struct seccomp_data *sd, |
181 | struct seccomp_filter **match) | |
e2cfabdf | 182 | { |
d39bd00d | 183 | struct seccomp_data sd_local; |
acf3b2c7 | 184 | u32 ret = SECCOMP_RET_ALLOW; |
8225d385 PK |
185 | /* Make sure cross-thread synced filter points somewhere sane. */ |
186 | struct seccomp_filter *f = | |
187 | lockless_dereference(current->seccomp.filter); | |
acf3b2c7 WD |
188 | |
189 | /* Ensure unexpected behavior doesn't result in failing open. */ | |
3ba2530c | 190 | if (unlikely(WARN_ON(f == NULL))) |
acf3b2c7 WD |
191 | return SECCOMP_RET_KILL; |
192 | ||
d39bd00d AL |
193 | if (!sd) { |
194 | populate_seccomp_data(&sd_local); | |
195 | sd = &sd_local; | |
196 | } | |
bd4cf0ed | 197 | |
e2cfabdf WD |
198 | /* |
199 | * All filters in the list are evaluated and the lowest BPF return | |
acf3b2c7 | 200 | * value always takes priority (ignoring the DATA). |
e2cfabdf | 201 | */ |
3ba2530c | 202 | for (; f; f = f->prev) { |
88575199 | 203 | u32 cur_ret = BPF_PROG_RUN(f->prog, sd); |
8f577cad | 204 | |
deb4de8b | 205 | if ((cur_ret & SECCOMP_RET_ACTION) < (ret & SECCOMP_RET_ACTION)) { |
acf3b2c7 | 206 | ret = cur_ret; |
deb4de8b KC |
207 | *match = f; |
208 | } | |
e2cfabdf WD |
209 | } |
210 | return ret; | |
211 | } | |
1f41b450 | 212 | #endif /* CONFIG_SECCOMP_FILTER */ |
e2cfabdf | 213 | |
1f41b450 KC |
214 | static inline bool seccomp_may_assign_mode(unsigned long seccomp_mode) |
215 | { | |
69f6a34b | 216 | assert_spin_locked(¤t->sighand->siglock); |
dbd95212 | 217 | |
1f41b450 KC |
218 | if (current->seccomp.mode && current->seccomp.mode != seccomp_mode) |
219 | return false; | |
220 | ||
221 | return true; | |
222 | } | |
223 | ||
3ba2530c KC |
224 | static inline void seccomp_assign_mode(struct task_struct *task, |
225 | unsigned long seccomp_mode) | |
1f41b450 | 226 | { |
69f6a34b | 227 | assert_spin_locked(&task->sighand->siglock); |
dbd95212 | 228 | |
3ba2530c KC |
229 | task->seccomp.mode = seccomp_mode; |
230 | /* | |
231 | * Make sure TIF_SECCOMP cannot be set before the mode (and | |
232 | * filter) is set. | |
233 | */ | |
234 | smp_mb__before_atomic(); | |
235 | set_tsk_thread_flag(task, TIF_SECCOMP); | |
1f41b450 KC |
236 | } |
237 | ||
238 | #ifdef CONFIG_SECCOMP_FILTER | |
c2e1f2e3 KC |
239 | /* Returns 1 if the parent is an ancestor of the child. */ |
240 | static int is_ancestor(struct seccomp_filter *parent, | |
241 | struct seccomp_filter *child) | |
242 | { | |
243 | /* NULL is the root ancestor. */ | |
244 | if (parent == NULL) | |
245 | return 1; | |
246 | for (; child; child = child->prev) | |
247 | if (child == parent) | |
248 | return 1; | |
249 | return 0; | |
250 | } | |
251 | ||
252 | /** | |
253 | * seccomp_can_sync_threads: checks if all threads can be synchronized | |
254 | * | |
255 | * Expects sighand and cred_guard_mutex locks to be held. | |
256 | * | |
257 | * Returns 0 on success, -ve on error, or the pid of a thread which was | |
258 | * either not in the correct seccomp mode or it did not have an ancestral | |
259 | * seccomp filter. | |
260 | */ | |
261 | static inline pid_t seccomp_can_sync_threads(void) | |
262 | { | |
263 | struct task_struct *thread, *caller; | |
264 | ||
265 | BUG_ON(!mutex_is_locked(¤t->signal->cred_guard_mutex)); | |
69f6a34b | 266 | assert_spin_locked(¤t->sighand->siglock); |
c2e1f2e3 KC |
267 | |
268 | /* Validate all threads being eligible for synchronization. */ | |
269 | caller = current; | |
270 | for_each_thread(caller, thread) { | |
271 | pid_t failed; | |
272 | ||
273 | /* Skip current, since it is initiating the sync. */ | |
274 | if (thread == caller) | |
275 | continue; | |
276 | ||
277 | if (thread->seccomp.mode == SECCOMP_MODE_DISABLED || | |
278 | (thread->seccomp.mode == SECCOMP_MODE_FILTER && | |
279 | is_ancestor(thread->seccomp.filter, | |
280 | caller->seccomp.filter))) | |
281 | continue; | |
282 | ||
283 | /* Return the first thread that cannot be synchronized. */ | |
284 | failed = task_pid_vnr(thread); | |
285 | /* If the pid cannot be resolved, then return -ESRCH */ | |
286 | if (unlikely(WARN_ON(failed == 0))) | |
287 | failed = -ESRCH; | |
288 | return failed; | |
289 | } | |
290 | ||
291 | return 0; | |
292 | } | |
293 | ||
294 | /** | |
295 | * seccomp_sync_threads: sets all threads to use current's filter | |
296 | * | |
297 | * Expects sighand and cred_guard_mutex locks to be held, and for | |
298 | * seccomp_can_sync_threads() to have returned success already | |
299 | * without dropping the locks. | |
300 | * | |
301 | */ | |
302 | static inline void seccomp_sync_threads(void) | |
303 | { | |
304 | struct task_struct *thread, *caller; | |
305 | ||
306 | BUG_ON(!mutex_is_locked(¤t->signal->cred_guard_mutex)); | |
69f6a34b | 307 | assert_spin_locked(¤t->sighand->siglock); |
c2e1f2e3 KC |
308 | |
309 | /* Synchronize all threads. */ | |
310 | caller = current; | |
311 | for_each_thread(caller, thread) { | |
312 | /* Skip current, since it needs no changes. */ | |
313 | if (thread == caller) | |
314 | continue; | |
315 | ||
316 | /* Get a task reference for the new leaf node. */ | |
317 | get_seccomp_filter(caller); | |
318 | /* | |
319 | * Drop the task reference to the shared ancestor since | |
320 | * current's path will hold a reference. (This also | |
321 | * allows a put before the assignment.) | |
322 | */ | |
323 | put_seccomp_filter(thread); | |
324 | smp_store_release(&thread->seccomp.filter, | |
325 | caller->seccomp.filter); | |
103502a3 JH |
326 | |
327 | /* | |
328 | * Don't let an unprivileged task work around | |
329 | * the no_new_privs restriction by creating | |
330 | * a thread that sets it up, enters seccomp, | |
331 | * then dies. | |
332 | */ | |
333 | if (task_no_new_privs(caller)) | |
334 | task_set_no_new_privs(thread); | |
335 | ||
c2e1f2e3 KC |
336 | /* |
337 | * Opt the other thread into seccomp if needed. | |
338 | * As threads are considered to be trust-realm | |
339 | * equivalent (see ptrace_may_access), it is safe to | |
340 | * allow one thread to transition the other. | |
341 | */ | |
103502a3 | 342 | if (thread->seccomp.mode == SECCOMP_MODE_DISABLED) |
c2e1f2e3 | 343 | seccomp_assign_mode(thread, SECCOMP_MODE_FILTER); |
c2e1f2e3 KC |
344 | } |
345 | } | |
346 | ||
e2cfabdf | 347 | /** |
c8bee430 | 348 | * seccomp_prepare_filter: Prepares a seccomp filter for use. |
e2cfabdf WD |
349 | * @fprog: BPF program to install |
350 | * | |
c8bee430 | 351 | * Returns filter on success or an ERR_PTR on failure. |
e2cfabdf | 352 | */ |
c8bee430 | 353 | static struct seccomp_filter *seccomp_prepare_filter(struct sock_fprog *fprog) |
e2cfabdf | 354 | { |
ac67eb2c DB |
355 | struct seccomp_filter *sfilter; |
356 | int ret; | |
97f2645f | 357 | const bool save_orig = IS_ENABLED(CONFIG_CHECKPOINT_RESTORE); |
e2cfabdf WD |
358 | |
359 | if (fprog->len == 0 || fprog->len > BPF_MAXINSNS) | |
c8bee430 | 360 | return ERR_PTR(-EINVAL); |
d9e12f42 | 361 | |
c8bee430 | 362 | BUG_ON(INT_MAX / fprog->len < sizeof(struct sock_filter)); |
e2cfabdf WD |
363 | |
364 | /* | |
119ce5c8 | 365 | * Installing a seccomp filter requires that the task has |
e2cfabdf WD |
366 | * CAP_SYS_ADMIN in its namespace or be running with no_new_privs. |
367 | * This avoids scenarios where unprivileged tasks can affect the | |
368 | * behavior of privileged children. | |
369 | */ | |
1d4457f9 | 370 | if (!task_no_new_privs(current) && |
e2cfabdf WD |
371 | security_capable_noaudit(current_cred(), current_user_ns(), |
372 | CAP_SYS_ADMIN) != 0) | |
c8bee430 | 373 | return ERR_PTR(-EACCES); |
e2cfabdf | 374 | |
bd4cf0ed | 375 | /* Allocate a new seccomp_filter */ |
ac67eb2c DB |
376 | sfilter = kzalloc(sizeof(*sfilter), GFP_KERNEL | __GFP_NOWARN); |
377 | if (!sfilter) | |
d9e12f42 | 378 | return ERR_PTR(-ENOMEM); |
ac67eb2c DB |
379 | |
380 | ret = bpf_prog_create_from_user(&sfilter->prog, fprog, | |
f8e529ed | 381 | seccomp_check_filter, save_orig); |
ac67eb2c DB |
382 | if (ret < 0) { |
383 | kfree(sfilter); | |
384 | return ERR_PTR(ret); | |
d9e12f42 | 385 | } |
bd4cf0ed | 386 | |
0b5fa229 | 387 | refcount_set(&sfilter->usage, 1); |
e2cfabdf | 388 | |
ac67eb2c | 389 | return sfilter; |
e2cfabdf WD |
390 | } |
391 | ||
392 | /** | |
c8bee430 | 393 | * seccomp_prepare_user_filter - prepares a user-supplied sock_fprog |
e2cfabdf WD |
394 | * @user_filter: pointer to the user data containing a sock_fprog. |
395 | * | |
396 | * Returns 0 on success and non-zero otherwise. | |
397 | */ | |
c8bee430 KC |
398 | static struct seccomp_filter * |
399 | seccomp_prepare_user_filter(const char __user *user_filter) | |
e2cfabdf WD |
400 | { |
401 | struct sock_fprog fprog; | |
c8bee430 | 402 | struct seccomp_filter *filter = ERR_PTR(-EFAULT); |
e2cfabdf WD |
403 | |
404 | #ifdef CONFIG_COMPAT | |
5c38065e | 405 | if (in_compat_syscall()) { |
e2cfabdf WD |
406 | struct compat_sock_fprog fprog32; |
407 | if (copy_from_user(&fprog32, user_filter, sizeof(fprog32))) | |
408 | goto out; | |
409 | fprog.len = fprog32.len; | |
410 | fprog.filter = compat_ptr(fprog32.filter); | |
411 | } else /* falls through to the if below. */ | |
412 | #endif | |
413 | if (copy_from_user(&fprog, user_filter, sizeof(fprog))) | |
414 | goto out; | |
c8bee430 | 415 | filter = seccomp_prepare_filter(&fprog); |
e2cfabdf | 416 | out: |
c8bee430 KC |
417 | return filter; |
418 | } | |
419 | ||
420 | /** | |
421 | * seccomp_attach_filter: validate and attach filter | |
422 | * @flags: flags to change filter behavior | |
423 | * @filter: seccomp filter to add to the current process | |
424 | * | |
dbd95212 KC |
425 | * Caller must be holding current->sighand->siglock lock. |
426 | * | |
c8bee430 KC |
427 | * Returns 0 on success, -ve on error. |
428 | */ | |
429 | static long seccomp_attach_filter(unsigned int flags, | |
430 | struct seccomp_filter *filter) | |
431 | { | |
432 | unsigned long total_insns; | |
433 | struct seccomp_filter *walker; | |
434 | ||
69f6a34b | 435 | assert_spin_locked(¤t->sighand->siglock); |
dbd95212 | 436 | |
c8bee430 KC |
437 | /* Validate resulting filter length. */ |
438 | total_insns = filter->prog->len; | |
439 | for (walker = current->seccomp.filter; walker; walker = walker->prev) | |
440 | total_insns += walker->prog->len + 4; /* 4 instr penalty */ | |
441 | if (total_insns > MAX_INSNS_PER_PATH) | |
442 | return -ENOMEM; | |
443 | ||
c2e1f2e3 KC |
444 | /* If thread sync has been requested, check that it is possible. */ |
445 | if (flags & SECCOMP_FILTER_FLAG_TSYNC) { | |
446 | int ret; | |
447 | ||
448 | ret = seccomp_can_sync_threads(); | |
449 | if (ret) | |
450 | return ret; | |
451 | } | |
452 | ||
c8bee430 KC |
453 | /* |
454 | * If there is an existing filter, make it the prev and don't drop its | |
455 | * task reference. | |
456 | */ | |
457 | filter->prev = current->seccomp.filter; | |
458 | current->seccomp.filter = filter; | |
459 | ||
c2e1f2e3 KC |
460 | /* Now that the new filter is in place, synchronize to all threads. */ |
461 | if (flags & SECCOMP_FILTER_FLAG_TSYNC) | |
462 | seccomp_sync_threads(); | |
463 | ||
c8bee430 | 464 | return 0; |
e2cfabdf WD |
465 | } |
466 | ||
467 | /* get_seccomp_filter - increments the reference count of the filter on @tsk */ | |
468 | void get_seccomp_filter(struct task_struct *tsk) | |
469 | { | |
470 | struct seccomp_filter *orig = tsk->seccomp.filter; | |
471 | if (!orig) | |
472 | return; | |
473 | /* Reference count is bounded by the number of total processes. */ | |
0b5fa229 | 474 | refcount_inc(&orig->usage); |
e2cfabdf WD |
475 | } |
476 | ||
c8bee430 KC |
477 | static inline void seccomp_filter_free(struct seccomp_filter *filter) |
478 | { | |
479 | if (filter) { | |
bab18991 | 480 | bpf_prog_destroy(filter->prog); |
c8bee430 KC |
481 | kfree(filter); |
482 | } | |
483 | } | |
484 | ||
e2cfabdf WD |
485 | /* put_seccomp_filter - decrements the ref count of tsk->seccomp.filter */ |
486 | void put_seccomp_filter(struct task_struct *tsk) | |
487 | { | |
488 | struct seccomp_filter *orig = tsk->seccomp.filter; | |
489 | /* Clean up single-reference branches iteratively. */ | |
0b5fa229 | 490 | while (orig && refcount_dec_and_test(&orig->usage)) { |
e2cfabdf WD |
491 | struct seccomp_filter *freeme = orig; |
492 | orig = orig->prev; | |
c8bee430 | 493 | seccomp_filter_free(freeme); |
e2cfabdf WD |
494 | } |
495 | } | |
bb6ea430 | 496 | |
b25e6716 MF |
497 | static void seccomp_init_siginfo(siginfo_t *info, int syscall, int reason) |
498 | { | |
499 | memset(info, 0, sizeof(*info)); | |
500 | info->si_signo = SIGSYS; | |
501 | info->si_code = SYS_SECCOMP; | |
502 | info->si_call_addr = (void __user *)KSTK_EIP(current); | |
503 | info->si_errno = reason; | |
504 | info->si_arch = syscall_get_arch(); | |
505 | info->si_syscall = syscall; | |
506 | } | |
507 | ||
bb6ea430 WD |
508 | /** |
509 | * seccomp_send_sigsys - signals the task to allow in-process syscall emulation | |
510 | * @syscall: syscall number to send to userland | |
511 | * @reason: filter-supplied reason code to send to userland (via si_errno) | |
512 | * | |
513 | * Forces a SIGSYS with a code of SYS_SECCOMP and related sigsys info. | |
514 | */ | |
515 | static void seccomp_send_sigsys(int syscall, int reason) | |
516 | { | |
517 | struct siginfo info; | |
b25e6716 | 518 | seccomp_init_siginfo(&info, syscall, reason); |
bb6ea430 WD |
519 | force_sig_info(SIGSYS, &info, current); |
520 | } | |
e2cfabdf | 521 | #endif /* CONFIG_SECCOMP_FILTER */ |
1da177e4 LT |
522 | |
523 | /* | |
524 | * Secure computing mode 1 allows only read/write/exit/sigreturn. | |
525 | * To be fully secure this must be combined with rlimit | |
526 | * to limit the stack allocations too. | |
527 | */ | |
cb4253aa | 528 | static const int mode1_syscalls[] = { |
1da177e4 LT |
529 | __NR_seccomp_read, __NR_seccomp_write, __NR_seccomp_exit, __NR_seccomp_sigreturn, |
530 | 0, /* null terminated */ | |
531 | }; | |
532 | ||
a4412fc9 | 533 | static void __secure_computing_strict(int this_syscall) |
1da177e4 | 534 | { |
cb4253aa | 535 | const int *syscall_whitelist = mode1_syscalls; |
a4412fc9 | 536 | #ifdef CONFIG_COMPAT |
5c38065e | 537 | if (in_compat_syscall()) |
c983f0e8 | 538 | syscall_whitelist = get_compat_mode1_syscalls(); |
a4412fc9 AL |
539 | #endif |
540 | do { | |
541 | if (*syscall_whitelist == this_syscall) | |
542 | return; | |
543 | } while (*++syscall_whitelist); | |
544 | ||
545 | #ifdef SECCOMP_DEBUG | |
546 | dump_stack(); | |
547 | #endif | |
548 | audit_seccomp(this_syscall, SIGKILL, SECCOMP_RET_KILL); | |
549 | do_exit(SIGKILL); | |
550 | } | |
551 | ||
552 | #ifndef CONFIG_HAVE_ARCH_SECCOMP_FILTER | |
553 | void secure_computing_strict(int this_syscall) | |
554 | { | |
555 | int mode = current->seccomp.mode; | |
556 | ||
97f2645f | 557 | if (IS_ENABLED(CONFIG_CHECKPOINT_RESTORE) && |
13c4a901 TA |
558 | unlikely(current->ptrace & PT_SUSPEND_SECCOMP)) |
559 | return; | |
560 | ||
221272f9 | 561 | if (mode == SECCOMP_MODE_DISABLED) |
a4412fc9 AL |
562 | return; |
563 | else if (mode == SECCOMP_MODE_STRICT) | |
564 | __secure_computing_strict(this_syscall); | |
565 | else | |
566 | BUG(); | |
567 | } | |
568 | #else | |
13aa72f0 AL |
569 | |
570 | #ifdef CONFIG_SECCOMP_FILTER | |
ce6526e8 KC |
571 | static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd, |
572 | const bool recheck_after_trace) | |
13aa72f0 AL |
573 | { |
574 | u32 filter_ret, action; | |
deb4de8b | 575 | struct seccomp_filter *match = NULL; |
13aa72f0 | 576 | int data; |
1da177e4 | 577 | |
3ba2530c KC |
578 | /* |
579 | * Make sure that any changes to mode from another thread have | |
580 | * been seen after TIF_SECCOMP was seen. | |
581 | */ | |
582 | rmb(); | |
583 | ||
deb4de8b | 584 | filter_ret = seccomp_run_filters(sd, &match); |
13aa72f0 AL |
585 | data = filter_ret & SECCOMP_RET_DATA; |
586 | action = filter_ret & SECCOMP_RET_ACTION; | |
587 | ||
588 | switch (action) { | |
589 | case SECCOMP_RET_ERRNO: | |
580c57f1 KC |
590 | /* Set low-order bits as an errno, capped at MAX_ERRNO. */ |
591 | if (data > MAX_ERRNO) | |
592 | data = MAX_ERRNO; | |
d39bd00d | 593 | syscall_set_return_value(current, task_pt_regs(current), |
13aa72f0 AL |
594 | -data, 0); |
595 | goto skip; | |
596 | ||
597 | case SECCOMP_RET_TRAP: | |
598 | /* Show the handler the original registers. */ | |
d39bd00d | 599 | syscall_rollback(current, task_pt_regs(current)); |
13aa72f0 AL |
600 | /* Let the filter pass back 16 bits of data. */ |
601 | seccomp_send_sigsys(this_syscall, data); | |
602 | goto skip; | |
603 | ||
604 | case SECCOMP_RET_TRACE: | |
ce6526e8 KC |
605 | /* We've been put in this state by the ptracer already. */ |
606 | if (recheck_after_trace) | |
607 | return 0; | |
608 | ||
8112c4f1 KC |
609 | /* ENOSYS these calls if there is no tracer attached. */ |
610 | if (!ptrace_event_enabled(current, PTRACE_EVENT_SECCOMP)) { | |
611 | syscall_set_return_value(current, | |
612 | task_pt_regs(current), | |
613 | -ENOSYS, 0); | |
614 | goto skip; | |
615 | } | |
616 | ||
617 | /* Allow the BPF to provide the event message */ | |
618 | ptrace_event(PTRACE_EVENT_SECCOMP, data); | |
619 | /* | |
620 | * The delivery of a fatal signal during event | |
485a252a KC |
621 | * notification may silently skip tracer notification, |
622 | * which could leave us with a potentially unmodified | |
623 | * syscall that the tracer would have liked to have | |
624 | * changed. Since the process is about to die, we just | |
625 | * force the syscall to be skipped and let the signal | |
626 | * kill the process and correctly handle any tracer exit | |
627 | * notifications. | |
8112c4f1 KC |
628 | */ |
629 | if (fatal_signal_pending(current)) | |
485a252a | 630 | goto skip; |
8112c4f1 KC |
631 | /* Check if the tracer forced the syscall to be skipped. */ |
632 | this_syscall = syscall_get_nr(current, task_pt_regs(current)); | |
633 | if (this_syscall < 0) | |
634 | goto skip; | |
635 | ||
ce6526e8 KC |
636 | /* |
637 | * Recheck the syscall, since it may have changed. This | |
638 | * intentionally uses a NULL struct seccomp_data to force | |
639 | * a reload of all registers. This does not goto skip since | |
640 | * a skip would have already been reported. | |
641 | */ | |
642 | if (__seccomp_filter(this_syscall, NULL, true)) | |
643 | return -1; | |
644 | ||
8112c4f1 | 645 | return 0; |
13aa72f0 AL |
646 | |
647 | case SECCOMP_RET_ALLOW: | |
deb4de8b KC |
648 | /* |
649 | * Note that the "match" filter will always be NULL for | |
650 | * this action since SECCOMP_RET_ALLOW is the starting | |
651 | * state in seccomp_run_filters(). | |
652 | */ | |
8112c4f1 | 653 | return 0; |
13aa72f0 AL |
654 | |
655 | case SECCOMP_RET_KILL: | |
131b6351 | 656 | default: |
13aa72f0 | 657 | audit_seccomp(this_syscall, SIGSYS, action); |
d7276e32 KC |
658 | /* Dump core only if this is the last remaining thread. */ |
659 | if (get_nr_threads(current) == 1) { | |
131b6351 KC |
660 | siginfo_t info; |
661 | ||
d7276e32 KC |
662 | /* Show the original registers in the dump. */ |
663 | syscall_rollback(current, task_pt_regs(current)); | |
664 | /* Trigger a manual coredump since do_exit skips it. */ | |
665 | seccomp_init_siginfo(&info, this_syscall, data); | |
666 | do_coredump(&info); | |
667 | } | |
13aa72f0 AL |
668 | do_exit(SIGSYS); |
669 | } | |
670 | ||
671 | unreachable(); | |
672 | ||
673 | skip: | |
674 | audit_seccomp(this_syscall, 0, action); | |
8112c4f1 KC |
675 | return -1; |
676 | } | |
677 | #else | |
ce6526e8 KC |
678 | static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd, |
679 | const bool recheck_after_trace) | |
8112c4f1 KC |
680 | { |
681 | BUG(); | |
13aa72f0 | 682 | } |
1da177e4 | 683 | #endif |
13aa72f0 | 684 | |
8112c4f1 | 685 | int __secure_computing(const struct seccomp_data *sd) |
13aa72f0 AL |
686 | { |
687 | int mode = current->seccomp.mode; | |
8112c4f1 | 688 | int this_syscall; |
13aa72f0 | 689 | |
97f2645f | 690 | if (IS_ENABLED(CONFIG_CHECKPOINT_RESTORE) && |
13c4a901 | 691 | unlikely(current->ptrace & PT_SUSPEND_SECCOMP)) |
8112c4f1 KC |
692 | return 0; |
693 | ||
694 | this_syscall = sd ? sd->nr : | |
695 | syscall_get_nr(current, task_pt_regs(current)); | |
13c4a901 | 696 | |
13aa72f0 | 697 | switch (mode) { |
e2cfabdf | 698 | case SECCOMP_MODE_STRICT: |
13aa72f0 | 699 | __secure_computing_strict(this_syscall); /* may call do_exit */ |
8112c4f1 | 700 | return 0; |
13aa72f0 | 701 | case SECCOMP_MODE_FILTER: |
ce6526e8 | 702 | return __seccomp_filter(this_syscall, sd, false); |
1da177e4 LT |
703 | default: |
704 | BUG(); | |
705 | } | |
13aa72f0 | 706 | } |
a4412fc9 | 707 | #endif /* CONFIG_HAVE_ARCH_SECCOMP_FILTER */ |
1d9d02fe AA |
708 | |
709 | long prctl_get_seccomp(void) | |
710 | { | |
711 | return current->seccomp.mode; | |
712 | } | |
713 | ||
e2cfabdf | 714 | /** |
3b23dd12 | 715 | * seccomp_set_mode_strict: internal function for setting strict seccomp |
e2cfabdf WD |
716 | * |
717 | * Once current->seccomp.mode is non-zero, it may not be changed. | |
718 | * | |
719 | * Returns 0 on success or -EINVAL on failure. | |
720 | */ | |
3b23dd12 | 721 | static long seccomp_set_mode_strict(void) |
1d9d02fe | 722 | { |
3b23dd12 | 723 | const unsigned long seccomp_mode = SECCOMP_MODE_STRICT; |
e2cfabdf | 724 | long ret = -EINVAL; |
1d9d02fe | 725 | |
dbd95212 KC |
726 | spin_lock_irq(¤t->sighand->siglock); |
727 | ||
1f41b450 | 728 | if (!seccomp_may_assign_mode(seccomp_mode)) |
1d9d02fe AA |
729 | goto out; |
730 | ||
cf99abac | 731 | #ifdef TIF_NOTSC |
3b23dd12 | 732 | disable_TSC(); |
cf99abac | 733 | #endif |
3ba2530c | 734 | seccomp_assign_mode(current, seccomp_mode); |
3b23dd12 KC |
735 | ret = 0; |
736 | ||
737 | out: | |
dbd95212 | 738 | spin_unlock_irq(¤t->sighand->siglock); |
3b23dd12 KC |
739 | |
740 | return ret; | |
741 | } | |
742 | ||
e2cfabdf | 743 | #ifdef CONFIG_SECCOMP_FILTER |
3b23dd12 KC |
744 | /** |
745 | * seccomp_set_mode_filter: internal function for setting seccomp filter | |
48dc92b9 | 746 | * @flags: flags to change filter behavior |
3b23dd12 KC |
747 | * @filter: struct sock_fprog containing filter |
748 | * | |
749 | * This function may be called repeatedly to install additional filters. | |
750 | * Every filter successfully installed will be evaluated (in reverse order) | |
751 | * for each system call the task makes. | |
752 | * | |
753 | * Once current->seccomp.mode is non-zero, it may not be changed. | |
754 | * | |
755 | * Returns 0 on success or -EINVAL on failure. | |
756 | */ | |
48dc92b9 KC |
757 | static long seccomp_set_mode_filter(unsigned int flags, |
758 | const char __user *filter) | |
3b23dd12 KC |
759 | { |
760 | const unsigned long seccomp_mode = SECCOMP_MODE_FILTER; | |
c8bee430 | 761 | struct seccomp_filter *prepared = NULL; |
3b23dd12 KC |
762 | long ret = -EINVAL; |
763 | ||
48dc92b9 | 764 | /* Validate flags. */ |
c2e1f2e3 | 765 | if (flags & ~SECCOMP_FILTER_FLAG_MASK) |
dbd95212 | 766 | return -EINVAL; |
48dc92b9 | 767 | |
c8bee430 KC |
768 | /* Prepare the new filter before holding any locks. */ |
769 | prepared = seccomp_prepare_user_filter(filter); | |
770 | if (IS_ERR(prepared)) | |
771 | return PTR_ERR(prepared); | |
772 | ||
c2e1f2e3 KC |
773 | /* |
774 | * Make sure we cannot change seccomp or nnp state via TSYNC | |
775 | * while another thread is in the middle of calling exec. | |
776 | */ | |
777 | if (flags & SECCOMP_FILTER_FLAG_TSYNC && | |
778 | mutex_lock_killable(¤t->signal->cred_guard_mutex)) | |
779 | goto out_free; | |
780 | ||
dbd95212 KC |
781 | spin_lock_irq(¤t->sighand->siglock); |
782 | ||
3b23dd12 KC |
783 | if (!seccomp_may_assign_mode(seccomp_mode)) |
784 | goto out; | |
785 | ||
c8bee430 | 786 | ret = seccomp_attach_filter(flags, prepared); |
3b23dd12 | 787 | if (ret) |
e2cfabdf | 788 | goto out; |
c8bee430 KC |
789 | /* Do not free the successfully attached filter. */ |
790 | prepared = NULL; | |
1d9d02fe | 791 | |
3ba2530c | 792 | seccomp_assign_mode(current, seccomp_mode); |
e2cfabdf | 793 | out: |
dbd95212 | 794 | spin_unlock_irq(¤t->sighand->siglock); |
c2e1f2e3 KC |
795 | if (flags & SECCOMP_FILTER_FLAG_TSYNC) |
796 | mutex_unlock(¤t->signal->cred_guard_mutex); | |
797 | out_free: | |
c8bee430 | 798 | seccomp_filter_free(prepared); |
1d9d02fe AA |
799 | return ret; |
800 | } | |
3b23dd12 | 801 | #else |
48dc92b9 KC |
802 | static inline long seccomp_set_mode_filter(unsigned int flags, |
803 | const char __user *filter) | |
3b23dd12 KC |
804 | { |
805 | return -EINVAL; | |
806 | } | |
807 | #endif | |
d78ab02c | 808 | |
48dc92b9 KC |
809 | /* Common entry point for both prctl and syscall. */ |
810 | static long do_seccomp(unsigned int op, unsigned int flags, | |
811 | const char __user *uargs) | |
812 | { | |
813 | switch (op) { | |
814 | case SECCOMP_SET_MODE_STRICT: | |
815 | if (flags != 0 || uargs != NULL) | |
816 | return -EINVAL; | |
817 | return seccomp_set_mode_strict(); | |
818 | case SECCOMP_SET_MODE_FILTER: | |
819 | return seccomp_set_mode_filter(flags, uargs); | |
820 | default: | |
821 | return -EINVAL; | |
822 | } | |
823 | } | |
824 | ||
825 | SYSCALL_DEFINE3(seccomp, unsigned int, op, unsigned int, flags, | |
826 | const char __user *, uargs) | |
827 | { | |
828 | return do_seccomp(op, flags, uargs); | |
829 | } | |
830 | ||
d78ab02c KC |
831 | /** |
832 | * prctl_set_seccomp: configures current->seccomp.mode | |
833 | * @seccomp_mode: requested mode to use | |
834 | * @filter: optional struct sock_fprog for use with SECCOMP_MODE_FILTER | |
835 | * | |
836 | * Returns 0 on success or -EINVAL on failure. | |
837 | */ | |
838 | long prctl_set_seccomp(unsigned long seccomp_mode, char __user *filter) | |
839 | { | |
48dc92b9 KC |
840 | unsigned int op; |
841 | char __user *uargs; | |
842 | ||
3b23dd12 KC |
843 | switch (seccomp_mode) { |
844 | case SECCOMP_MODE_STRICT: | |
48dc92b9 KC |
845 | op = SECCOMP_SET_MODE_STRICT; |
846 | /* | |
847 | * Setting strict mode through prctl always ignored filter, | |
848 | * so make sure it is always NULL here to pass the internal | |
849 | * check in do_seccomp(). | |
850 | */ | |
851 | uargs = NULL; | |
852 | break; | |
3b23dd12 | 853 | case SECCOMP_MODE_FILTER: |
48dc92b9 KC |
854 | op = SECCOMP_SET_MODE_FILTER; |
855 | uargs = filter; | |
856 | break; | |
3b23dd12 KC |
857 | default: |
858 | return -EINVAL; | |
859 | } | |
48dc92b9 KC |
860 | |
861 | /* prctl interface doesn't have flags, so they are always zero. */ | |
862 | return do_seccomp(op, 0, uargs); | |
d78ab02c | 863 | } |
f8e529ed TA |
864 | |
865 | #if defined(CONFIG_SECCOMP_FILTER) && defined(CONFIG_CHECKPOINT_RESTORE) | |
866 | long seccomp_get_filter(struct task_struct *task, unsigned long filter_off, | |
867 | void __user *data) | |
868 | { | |
869 | struct seccomp_filter *filter; | |
870 | struct sock_fprog_kern *fprog; | |
871 | long ret; | |
872 | unsigned long count = 0; | |
873 | ||
874 | if (!capable(CAP_SYS_ADMIN) || | |
875 | current->seccomp.mode != SECCOMP_MODE_DISABLED) { | |
876 | return -EACCES; | |
877 | } | |
878 | ||
879 | spin_lock_irq(&task->sighand->siglock); | |
880 | if (task->seccomp.mode != SECCOMP_MODE_FILTER) { | |
881 | ret = -EINVAL; | |
882 | goto out; | |
883 | } | |
884 | ||
885 | filter = task->seccomp.filter; | |
886 | while (filter) { | |
887 | filter = filter->prev; | |
888 | count++; | |
889 | } | |
890 | ||
891 | if (filter_off >= count) { | |
892 | ret = -ENOENT; | |
893 | goto out; | |
894 | } | |
895 | count -= filter_off; | |
896 | ||
897 | filter = task->seccomp.filter; | |
898 | while (filter && count > 1) { | |
899 | filter = filter->prev; | |
900 | count--; | |
901 | } | |
902 | ||
903 | if (WARN_ON(count != 1 || !filter)) { | |
904 | /* The filter tree shouldn't shrink while we're using it. */ | |
905 | ret = -ENOENT; | |
906 | goto out; | |
907 | } | |
908 | ||
909 | fprog = filter->prog->orig_prog; | |
910 | if (!fprog) { | |
470bf1f2 | 911 | /* This must be a new non-cBPF filter, since we save |
f8e529ed TA |
912 | * every cBPF filter's orig_prog above when |
913 | * CONFIG_CHECKPOINT_RESTORE is enabled. | |
914 | */ | |
915 | ret = -EMEDIUMTYPE; | |
916 | goto out; | |
917 | } | |
918 | ||
919 | ret = fprog->len; | |
920 | if (!data) | |
921 | goto out; | |
922 | ||
923 | get_seccomp_filter(task); | |
924 | spin_unlock_irq(&task->sighand->siglock); | |
925 | ||
926 | if (copy_to_user(data, fprog->filter, bpf_classic_proglen(fprog))) | |
927 | ret = -EFAULT; | |
928 | ||
929 | put_seccomp_filter(task); | |
930 | return ret; | |
931 | ||
932 | out: | |
933 | spin_unlock_irq(&task->sighand->siglock); | |
934 | return ret; | |
935 | } | |
936 | #endif |