1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Copyright (C) 1991, 1992 Linus Torvalds
4 *
5 * 1997-11-28 Modified for POSIX.1b signals by Richard Henderson
6 * 2000-06-20 Pentium III FXSR, SSE support by Gareth Hughes
7 * 2000-12-* x86-64 compatibility mode signal handling by Andi Kleen
8 */
9
10 #include <linux/sched.h>
11 #include <linux/sched/task_stack.h>
12 #include <linux/mm.h>
13 #include <linux/smp.h>
14 #include <linux/kernel.h>
15 #include <linux/errno.h>
16 #include <linux/wait.h>
17 #include <linux/unistd.h>
18 #include <linux/stddef.h>
19 #include <linux/personality.h>
20 #include <linux/compat.h>
21 #include <linux/binfmts.h>
22 #include <linux/syscalls.h>
23 #include <asm/ucontext.h>
24 #include <linux/uaccess.h>
25 #include <asm/fpu/signal.h>
26 #include <asm/ptrace.h>
27 #include <asm/user32.h>
28 #include <uapi/asm/sigcontext.h>
29 #include <asm/proto.h>
30 #include <asm/vdso.h>
31 #include <asm/sigframe.h>
32 #include <asm/sighandling.h>
33 #include <asm/smap.h>
34 #include <asm/gsseg.h>
35
36 /*
37 * The first GDT descriptor is reserved as 'NULL descriptor'. As bits 0
38 * and 1 of a segment selector, i.e., the RPL bits, are NOT used to index
39 * GDT, selector values 0~3 all point to the NULL descriptor, thus values
40 * 0, 1, 2 and 3 are all valid NULL selector values.
41 *
42 * However IRET zeros ES, FS, GS, and DS segment registers if any of them
43 * is found to have any nonzero NULL selector value, which can be used by
44 * userspace in pre-FRED systems to spot any interrupt/exception by loading
45 * a nonzero NULL selector and waiting for it to become zero. Before FRED
46 * there was nothing software could do to prevent such an information leak.
47 *
48 * ERETU, the only legit instruction to return to userspace from kernel
49 * under FRED, by design does NOT zero any segment register to avoid this
50 * problem behavior.
51 *
52 * As such, leave NULL selector values 0~3 unchanged.
53 */
fixup_rpl(u16 sel)54 static inline u16 fixup_rpl(u16 sel)
55 {
56 return sel <= 3 ? sel : sel | 3;
57 }
58
59 #ifdef CONFIG_IA32_EMULATION
60 #include <asm/unistd_32_ia32.h>
61
reload_segments(struct sigcontext_32 * sc)62 static inline void reload_segments(struct sigcontext_32 *sc)
63 {
64 u16 cur;
65
66 /*
67 * Reload fs and gs if they have changed in the signal
68 * handler. This does not handle long fs/gs base changes in
69 * the handler, but does not clobber them at least in the
70 * normal case.
71 */
72 savesegment(gs, cur);
73 if (fixup_rpl(sc->gs) != cur)
74 load_gs_index(fixup_rpl(sc->gs));
75 savesegment(fs, cur);
76 if (fixup_rpl(sc->fs) != cur)
77 loadsegment(fs, fixup_rpl(sc->fs));
78
79 savesegment(ds, cur);
80 if (fixup_rpl(sc->ds) != cur)
81 loadsegment(ds, fixup_rpl(sc->ds));
82 savesegment(es, cur);
83 if (fixup_rpl(sc->es) != cur)
84 loadsegment(es, fixup_rpl(sc->es));
85 }
86
87 #define sigset32_t compat_sigset_t
88 #define siginfo32_t compat_siginfo_t
89 #define restore_altstack32 compat_restore_altstack
90 #define unsafe_save_altstack32 unsafe_compat_save_altstack
91
92 #else
93
94 #define sigset32_t sigset_t
95 #define siginfo32_t siginfo_t
96 #define __NR_ia32_sigreturn __NR_sigreturn
97 #define __NR_ia32_rt_sigreturn __NR_rt_sigreturn
98 #define restore_altstack32 restore_altstack
99 #define unsafe_save_altstack32 unsafe_save_altstack
100 #define __copy_siginfo_to_user32 copy_siginfo_to_user
101
102 #endif
103
104 /*
105 * Do a signal return; undo the signal stack.
106 */
ia32_restore_sigcontext(struct pt_regs * regs,struct sigcontext_32 __user * usc)107 static bool ia32_restore_sigcontext(struct pt_regs *regs,
108 struct sigcontext_32 __user *usc)
109 {
110 struct sigcontext_32 sc;
111
112 /* Always make any pending restarted system calls return -EINTR */
113 current->restart_block.fn = do_no_restart_syscall;
114
115 if (unlikely(copy_from_user(&sc, usc, sizeof(sc))))
116 return false;
117
118 /* Get only the ia32 registers. */
119 regs->bx = sc.bx;
120 regs->cx = sc.cx;
121 regs->dx = sc.dx;
122 regs->si = sc.si;
123 regs->di = sc.di;
124 regs->bp = sc.bp;
125 regs->ax = sc.ax;
126 regs->sp = sc.sp;
127 regs->ip = sc.ip;
128
129 /* Get CS/SS and force CPL3 */
130 regs->cs = sc.cs | 0x03;
131 regs->ss = sc.ss | 0x03;
132
133 regs->flags = (regs->flags & ~FIX_EFLAGS) | (sc.flags & FIX_EFLAGS);
134 /* disable syscall checks */
135 regs->orig_ax = -1;
136
137 #ifdef CONFIG_IA32_EMULATION
138 reload_segments(&sc);
139 #else
140 loadsegment(gs, fixup_rpl(sc.gs));
141 regs->fs = fixup_rpl(sc.fs);
142 regs->es = fixup_rpl(sc.es);
143 regs->ds = fixup_rpl(sc.ds);
144 #endif
145
146 return fpu__restore_sig(compat_ptr(sc.fpstate), 1);
147 }
148
SYSCALL32_DEFINE0(sigreturn)149 SYSCALL32_DEFINE0(sigreturn)
150 {
151 struct pt_regs *regs = current_pt_regs();
152 struct sigframe_ia32 __user *frame = (struct sigframe_ia32 __user *)(regs->sp-8);
153 sigset_t set;
154
155 if (!access_ok(frame, sizeof(*frame)))
156 goto badframe;
157 if (__get_user(set.sig[0], &frame->sc.oldmask)
158 || __get_user(((__u32 *)&set)[1], &frame->extramask[0]))
159 goto badframe;
160
161 set_current_blocked(&set);
162
163 if (!ia32_restore_sigcontext(regs, &frame->sc))
164 goto badframe;
165 return regs->ax;
166
167 badframe:
168 signal_fault(regs, frame, "32bit sigreturn");
169 return 0;
170 }
171
SYSCALL32_DEFINE0(rt_sigreturn)172 SYSCALL32_DEFINE0(rt_sigreturn)
173 {
174 struct pt_regs *regs = current_pt_regs();
175 struct rt_sigframe_ia32 __user *frame;
176 sigset_t set;
177
178 frame = (struct rt_sigframe_ia32 __user *)(regs->sp - 4);
179
180 if (!access_ok(frame, sizeof(*frame)))
181 goto badframe;
182 if (__get_user(*(__u64 *)&set, (__u64 __user *)&frame->uc.uc_sigmask))
183 goto badframe;
184
185 set_current_blocked(&set);
186
187 if (!ia32_restore_sigcontext(regs, &frame->uc.uc_mcontext))
188 goto badframe;
189
190 if (restore_altstack32(&frame->uc.uc_stack))
191 goto badframe;
192
193 return regs->ax;
194
195 badframe:
196 signal_fault(regs, frame, "32bit rt sigreturn");
197 return 0;
198 }
199
200 /*
201 * Set up a signal frame.
202 */
203
204 #define get_user_seg(seg) ({ unsigned int v; savesegment(seg, v); v; })
205
206 static __always_inline int
__unsafe_setup_sigcontext32(struct sigcontext_32 __user * sc,void __user * fpstate,struct pt_regs * regs,unsigned int mask)207 __unsafe_setup_sigcontext32(struct sigcontext_32 __user *sc,
208 void __user *fpstate,
209 struct pt_regs *regs, unsigned int mask)
210 {
211 unsafe_put_user(get_user_seg(gs), (unsigned int __user *)&sc->gs, Efault);
212 #ifdef CONFIG_IA32_EMULATION
213 unsafe_put_user(get_user_seg(fs), (unsigned int __user *)&sc->fs, Efault);
214 unsafe_put_user(get_user_seg(ds), (unsigned int __user *)&sc->ds, Efault);
215 unsafe_put_user(get_user_seg(es), (unsigned int __user *)&sc->es, Efault);
216 #else
217 unsafe_put_user(regs->fs, (unsigned int __user *)&sc->fs, Efault);
218 unsafe_put_user(regs->es, (unsigned int __user *)&sc->es, Efault);
219 unsafe_put_user(regs->ds, (unsigned int __user *)&sc->ds, Efault);
220 #endif
221
222 unsafe_put_user(regs->di, &sc->di, Efault);
223 unsafe_put_user(regs->si, &sc->si, Efault);
224 unsafe_put_user(regs->bp, &sc->bp, Efault);
225 unsafe_put_user(regs->sp, &sc->sp, Efault);
226 unsafe_put_user(regs->bx, &sc->bx, Efault);
227 unsafe_put_user(regs->dx, &sc->dx, Efault);
228 unsafe_put_user(regs->cx, &sc->cx, Efault);
229 unsafe_put_user(regs->ax, &sc->ax, Efault);
230 unsafe_put_user(current->thread.trap_nr, &sc->trapno, Efault);
231 unsafe_put_user(current->thread.error_code, &sc->err, Efault);
232 unsafe_put_user(regs->ip, &sc->ip, Efault);
233 unsafe_put_user(regs->cs, (unsigned int __user *)&sc->cs, Efault);
234 unsafe_put_user(regs->flags, &sc->flags, Efault);
235 unsafe_put_user(regs->sp, &sc->sp_at_signal, Efault);
236 unsafe_put_user(regs->ss, (unsigned int __user *)&sc->ss, Efault);
237
238 unsafe_put_user(ptr_to_compat(fpstate), &sc->fpstate, Efault);
239
240 /* non-iBCS2 extensions.. */
241 unsafe_put_user(mask, &sc->oldmask, Efault);
242 unsafe_put_user(current->thread.cr2, &sc->cr2, Efault);
243 return 0;
244
245 Efault:
246 return -EFAULT;
247 }
248
249 #define unsafe_put_sigcontext32(sc, fp, regs, set, label) \
250 do { \
251 if (__unsafe_setup_sigcontext32(sc, fp, regs, set->sig[0])) \
252 goto label; \
253 } while(0)
254
ia32_setup_frame(struct ksignal * ksig,struct pt_regs * regs)255 int ia32_setup_frame(struct ksignal *ksig, struct pt_regs *regs)
256 {
257 sigset32_t *set = (sigset32_t *) sigmask_to_save();
258 struct sigframe_ia32 __user *frame;
259 void __user *restorer;
260 void __user *fp = NULL;
261
262 /* copy_to_user optimizes that into a single 8 byte store */
263 static const struct {
264 u16 poplmovl;
265 u32 val;
266 u16 int80;
267 } __attribute__((packed)) code = {
268 0xb858, /* popl %eax ; movl $...,%eax */
269 __NR_ia32_sigreturn,
270 0x80cd, /* int $0x80 */
271 };
272
273 frame = get_sigframe(ksig, regs, sizeof(*frame), &fp);
274
275 if (ksig->ka.sa.sa_flags & SA_RESTORER) {
276 restorer = ksig->ka.sa.sa_restorer;
277 } else {
278 /* Return stub is in 32bit vsyscall page */
279 if (current->mm->context.vdso)
280 restorer = current->mm->context.vdso +
281 vdso_image_32.sym___kernel_sigreturn;
282 else
283 restorer = &frame->retcode;
284 }
285
286 if (!user_access_begin(frame, sizeof(*frame)))
287 return -EFAULT;
288
289 unsafe_put_user(ksig->sig, &frame->sig, Efault);
290 unsafe_put_sigcontext32(&frame->sc, fp, regs, set, Efault);
291 unsafe_put_user(set->sig[1], &frame->extramask[0], Efault);
292 unsafe_put_user(ptr_to_compat(restorer), &frame->pretcode, Efault);
293 /*
294 * These are actually not used anymore, but left because some
295 * gdb versions depend on them as a marker.
296 */
297 unsafe_put_user(*((u64 *)&code), (u64 __user *)frame->retcode, Efault);
298 user_access_end();
299
300 /* Set up registers for signal handler */
301 regs->sp = (unsigned long) frame;
302 regs->ip = (unsigned long) ksig->ka.sa.sa_handler;
303
304 /* Make -mregparm=3 work */
305 regs->ax = ksig->sig;
306 regs->dx = 0;
307 regs->cx = 0;
308
309 #ifdef CONFIG_IA32_EMULATION
310 loadsegment(ds, __USER_DS);
311 loadsegment(es, __USER_DS);
312 #else
313 regs->ds = __USER_DS;
314 regs->es = __USER_DS;
315 #endif
316
317 regs->cs = __USER32_CS;
318 regs->ss = __USER_DS;
319
320 return 0;
321 Efault:
322 user_access_end();
323 return -EFAULT;
324 }
325
ia32_setup_rt_frame(struct ksignal * ksig,struct pt_regs * regs)326 int ia32_setup_rt_frame(struct ksignal *ksig, struct pt_regs *regs)
327 {
328 sigset32_t *set = (sigset32_t *) sigmask_to_save();
329 struct rt_sigframe_ia32 __user *frame;
330 void __user *restorer;
331 void __user *fp = NULL;
332
333 /* unsafe_put_user optimizes that into a single 8 byte store */
334 static const struct {
335 u8 movl;
336 u32 val;
337 u16 int80;
338 u8 pad;
339 } __attribute__((packed)) code = {
340 0xb8,
341 __NR_ia32_rt_sigreturn,
342 0x80cd,
343 0,
344 };
345
346 frame = get_sigframe(ksig, regs, sizeof(*frame), &fp);
347
348 if (!user_access_begin(frame, sizeof(*frame)))
349 return -EFAULT;
350
351 unsafe_put_user(ksig->sig, &frame->sig, Efault);
352 unsafe_put_user(ptr_to_compat(&frame->info), &frame->pinfo, Efault);
353 unsafe_put_user(ptr_to_compat(&frame->uc), &frame->puc, Efault);
354
355 /* Create the ucontext. */
356 if (static_cpu_has(X86_FEATURE_XSAVE))
357 unsafe_put_user(UC_FP_XSTATE, &frame->uc.uc_flags, Efault);
358 else
359 unsafe_put_user(0, &frame->uc.uc_flags, Efault);
360 unsafe_put_user(0, &frame->uc.uc_link, Efault);
361 unsafe_save_altstack32(&frame->uc.uc_stack, regs->sp, Efault);
362
363 if (ksig->ka.sa.sa_flags & SA_RESTORER)
364 restorer = ksig->ka.sa.sa_restorer;
365 else
366 restorer = current->mm->context.vdso +
367 vdso_image_32.sym___kernel_rt_sigreturn;
368 unsafe_put_user(ptr_to_compat(restorer), &frame->pretcode, Efault);
369
370 /*
371 * Not actually used anymore, but left because some gdb
372 * versions need it.
373 */
374 unsafe_put_user(*((u64 *)&code), (u64 __user *)frame->retcode, Efault);
375 unsafe_put_sigcontext32(&frame->uc.uc_mcontext, fp, regs, set, Efault);
376 unsafe_put_user(*(__u64 *)set, (__u64 __user *)&frame->uc.uc_sigmask, Efault);
377 user_access_end();
378
379 if (__copy_siginfo_to_user32(&frame->info, &ksig->info))
380 return -EFAULT;
381
382 /* Set up registers for signal handler */
383 regs->sp = (unsigned long) frame;
384 regs->ip = (unsigned long) ksig->ka.sa.sa_handler;
385
386 /* Make -mregparm=3 work */
387 regs->ax = ksig->sig;
388 regs->dx = (unsigned long) &frame->info;
389 regs->cx = (unsigned long) &frame->uc;
390
391 #ifdef CONFIG_IA32_EMULATION
392 loadsegment(ds, __USER_DS);
393 loadsegment(es, __USER_DS);
394 #else
395 regs->ds = __USER_DS;
396 regs->es = __USER_DS;
397 #endif
398
399 regs->cs = __USER32_CS;
400 regs->ss = __USER_DS;
401
402 return 0;
403 Efault:
404 user_access_end();
405 return -EFAULT;
406 }
407
408 /*
409 * The siginfo_t structure and handing code is very easy
410 * to break in several ways. It must always be updated when new
411 * updates are made to the main siginfo_t, and
412 * copy_siginfo_to_user32() must be updated when the
413 * (arch-independent) copy_siginfo_to_user() is updated.
414 *
415 * It is also easy to put a new member in the siginfo_t
416 * which has implicit alignment which can move internal structure
417 * alignment around breaking the ABI. This can happen if you,
418 * for instance, put a plain 64-bit value in there.
419 */
420
421 /*
422 * If adding a new si_code, there is probably new data in
423 * the siginfo. Make sure folks bumping the si_code
424 * limits also have to look at this code. Make sure any
425 * new fields are handled in copy_siginfo_to_user32()!
426 */
427 static_assert(NSIGILL == 11);
428 static_assert(NSIGFPE == 15);
429 static_assert(NSIGSEGV == 10);
430 static_assert(NSIGBUS == 5);
431 static_assert(NSIGTRAP == 6);
432 static_assert(NSIGCHLD == 6);
433 static_assert(NSIGSYS == 2);
434
435 /* This is part of the ABI and can never change in size: */
436 static_assert(sizeof(siginfo32_t) == 128);
437
438 /* This is a part of the ABI and can never change in alignment */
439 static_assert(__alignof__(siginfo32_t) == 4);
440
441 /*
442 * The offsets of all the (unioned) si_fields are fixed
443 * in the ABI, of course. Make sure none of them ever
444 * move and are always at the beginning:
445 */
446 static_assert(offsetof(siginfo32_t, _sifields) == 3 * sizeof(int));
447
448 static_assert(offsetof(siginfo32_t, si_signo) == 0);
449 static_assert(offsetof(siginfo32_t, si_errno) == 4);
450 static_assert(offsetof(siginfo32_t, si_code) == 8);
451
452 /*
453 * Ensure that the size of each si_field never changes.
454 * If it does, it is a sign that the
455 * copy_siginfo_to_user32() code below needs to updated
456 * along with the size in the CHECK_SI_SIZE().
457 *
458 * We repeat this check for both the generic and compat
459 * siginfos.
460 *
461 * Note: it is OK for these to grow as long as the whole
462 * structure stays within the padding size (checked
463 * above).
464 */
465
466 #define CHECK_SI_OFFSET(name) \
467 static_assert(offsetof(siginfo32_t, _sifields) == \
468 offsetof(siginfo32_t, _sifields.name))
469
470 #define CHECK_SI_SIZE(name, size) \
471 static_assert(sizeof_field(siginfo32_t, _sifields.name) == size)
472
473 CHECK_SI_OFFSET(_kill);
474 CHECK_SI_SIZE (_kill, 2*sizeof(int));
475 static_assert(offsetof(siginfo32_t, si_pid) == 0xC);
476 static_assert(offsetof(siginfo32_t, si_uid) == 0x10);
477
478 CHECK_SI_OFFSET(_timer);
479 #ifdef CONFIG_COMPAT
480 /* compat_siginfo_t doesn't have si_sys_private */
481 CHECK_SI_SIZE (_timer, 3*sizeof(int));
482 #else
483 CHECK_SI_SIZE (_timer, 4*sizeof(int));
484 #endif
485 static_assert(offsetof(siginfo32_t, si_tid) == 0x0C);
486 static_assert(offsetof(siginfo32_t, si_overrun) == 0x10);
487 static_assert(offsetof(siginfo32_t, si_value) == 0x14);
488
489 CHECK_SI_OFFSET(_rt);
490 CHECK_SI_SIZE (_rt, 3*sizeof(int));
491 static_assert(offsetof(siginfo32_t, si_pid) == 0x0C);
492 static_assert(offsetof(siginfo32_t, si_uid) == 0x10);
493 static_assert(offsetof(siginfo32_t, si_value) == 0x14);
494
495 CHECK_SI_OFFSET(_sigchld);
496 CHECK_SI_SIZE (_sigchld, 5*sizeof(int));
497 static_assert(offsetof(siginfo32_t, si_pid) == 0x0C);
498 static_assert(offsetof(siginfo32_t, si_uid) == 0x10);
499 static_assert(offsetof(siginfo32_t, si_status) == 0x14);
500 static_assert(offsetof(siginfo32_t, si_utime) == 0x18);
501 static_assert(offsetof(siginfo32_t, si_stime) == 0x1C);
502
503 CHECK_SI_OFFSET(_sigfault);
504 CHECK_SI_SIZE (_sigfault, 4*sizeof(int));
505 static_assert(offsetof(siginfo32_t, si_addr) == 0x0C);
506
507 static_assert(offsetof(siginfo32_t, si_trapno) == 0x10);
508
509 static_assert(offsetof(siginfo32_t, si_addr_lsb) == 0x10);
510
511 static_assert(offsetof(siginfo32_t, si_lower) == 0x14);
512 static_assert(offsetof(siginfo32_t, si_upper) == 0x18);
513
514 static_assert(offsetof(siginfo32_t, si_pkey) == 0x14);
515
516 static_assert(offsetof(siginfo32_t, si_perf_data) == 0x10);
517 static_assert(offsetof(siginfo32_t, si_perf_type) == 0x14);
518 static_assert(offsetof(siginfo32_t, si_perf_flags) == 0x18);
519
520 CHECK_SI_OFFSET(_sigpoll);
521 CHECK_SI_SIZE (_sigpoll, 2*sizeof(int));
522 static_assert(offsetof(siginfo32_t, si_band) == 0x0C);
523 static_assert(offsetof(siginfo32_t, si_fd) == 0x10);
524
525 CHECK_SI_OFFSET(_sigsys);
526 CHECK_SI_SIZE (_sigsys, 3*sizeof(int));
527 static_assert(offsetof(siginfo32_t, si_call_addr) == 0x0C);
528 static_assert(offsetof(siginfo32_t, si_syscall) == 0x10);
529 static_assert(offsetof(siginfo32_t, si_arch) == 0x14);
530
531 /* any new si_fields should be added here */
532