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 prevent_single_step_upon_eretu(regs);
156
157 if (!access_ok(frame, sizeof(*frame)))
158 goto badframe;
159 if (__get_user(set.sig[0], &frame->sc.oldmask)
160 || __get_user(((__u32 *)&set)[1], &frame->extramask[0]))
161 goto badframe;
162
163 set_current_blocked(&set);
164
165 if (!ia32_restore_sigcontext(regs, &frame->sc))
166 goto badframe;
167 return regs->ax;
168
169 badframe:
170 signal_fault(regs, frame, "32bit sigreturn");
171 return 0;
172 }
173
SYSCALL32_DEFINE0(rt_sigreturn)174 SYSCALL32_DEFINE0(rt_sigreturn)
175 {
176 struct pt_regs *regs = current_pt_regs();
177 struct rt_sigframe_ia32 __user *frame;
178 sigset_t set;
179
180 prevent_single_step_upon_eretu(regs);
181
182 frame = (struct rt_sigframe_ia32 __user *)(regs->sp - 4);
183
184 if (!access_ok(frame, sizeof(*frame)))
185 goto badframe;
186 if (__get_user(*(__u64 *)&set, (__u64 __user *)&frame->uc.uc_sigmask))
187 goto badframe;
188
189 set_current_blocked(&set);
190
191 if (!ia32_restore_sigcontext(regs, &frame->uc.uc_mcontext))
192 goto badframe;
193
194 if (restore_altstack32(&frame->uc.uc_stack))
195 goto badframe;
196
197 return regs->ax;
198
199 badframe:
200 signal_fault(regs, frame, "32bit rt sigreturn");
201 return 0;
202 }
203
204 /*
205 * Set up a signal frame.
206 */
207
208 #define get_user_seg(seg) ({ unsigned int v; savesegment(seg, v); v; })
209
210 static __always_inline int
__unsafe_setup_sigcontext32(struct sigcontext_32 __user * sc,void __user * fpstate,struct pt_regs * regs,unsigned int mask)211 __unsafe_setup_sigcontext32(struct sigcontext_32 __user *sc,
212 void __user *fpstate,
213 struct pt_regs *regs, unsigned int mask)
214 {
215 unsafe_put_user(get_user_seg(gs), (unsigned int __user *)&sc->gs, Efault);
216 #ifdef CONFIG_IA32_EMULATION
217 unsafe_put_user(get_user_seg(fs), (unsigned int __user *)&sc->fs, Efault);
218 unsafe_put_user(get_user_seg(ds), (unsigned int __user *)&sc->ds, Efault);
219 unsafe_put_user(get_user_seg(es), (unsigned int __user *)&sc->es, Efault);
220 #else
221 unsafe_put_user(regs->fs, (unsigned int __user *)&sc->fs, Efault);
222 unsafe_put_user(regs->es, (unsigned int __user *)&sc->es, Efault);
223 unsafe_put_user(regs->ds, (unsigned int __user *)&sc->ds, Efault);
224 #endif
225
226 unsafe_put_user(regs->di, &sc->di, Efault);
227 unsafe_put_user(regs->si, &sc->si, Efault);
228 unsafe_put_user(regs->bp, &sc->bp, Efault);
229 unsafe_put_user(regs->sp, &sc->sp, Efault);
230 unsafe_put_user(regs->bx, &sc->bx, Efault);
231 unsafe_put_user(regs->dx, &sc->dx, Efault);
232 unsafe_put_user(regs->cx, &sc->cx, Efault);
233 unsafe_put_user(regs->ax, &sc->ax, Efault);
234 unsafe_put_user(current->thread.trap_nr, &sc->trapno, Efault);
235 unsafe_put_user(current->thread.error_code, &sc->err, Efault);
236 unsafe_put_user(regs->ip, &sc->ip, Efault);
237 unsafe_put_user(regs->cs, (unsigned int __user *)&sc->cs, Efault);
238 unsafe_put_user(regs->flags, &sc->flags, Efault);
239 unsafe_put_user(regs->sp, &sc->sp_at_signal, Efault);
240 unsafe_put_user(regs->ss, (unsigned int __user *)&sc->ss, Efault);
241
242 unsafe_put_user(ptr_to_compat(fpstate), &sc->fpstate, Efault);
243
244 /* non-iBCS2 extensions.. */
245 unsafe_put_user(mask, &sc->oldmask, Efault);
246 unsafe_put_user(current->thread.cr2, &sc->cr2, Efault);
247 return 0;
248
249 Efault:
250 return -EFAULT;
251 }
252
253 #define unsafe_put_sigcontext32(sc, fp, regs, set, label) \
254 do { \
255 if (__unsafe_setup_sigcontext32(sc, fp, regs, set->sig[0])) \
256 goto label; \
257 } while(0)
258
ia32_setup_frame(struct ksignal * ksig,struct pt_regs * regs)259 int ia32_setup_frame(struct ksignal *ksig, struct pt_regs *regs)
260 {
261 sigset32_t *set = (sigset32_t *) sigmask_to_save();
262 struct sigframe_ia32 __user *frame;
263 void __user *restorer;
264 void __user *fp = NULL;
265
266 /* copy_to_user optimizes that into a single 8 byte store */
267 static const struct {
268 u16 poplmovl;
269 u32 val;
270 u16 int80;
271 } __attribute__((packed)) code = {
272 0xb858, /* popl %eax ; movl $...,%eax */
273 __NR_ia32_sigreturn,
274 0x80cd, /* int $0x80 */
275 };
276
277 frame = get_sigframe(ksig, regs, sizeof(*frame), &fp);
278
279 if (ksig->ka.sa.sa_flags & SA_RESTORER) {
280 restorer = ksig->ka.sa.sa_restorer;
281 } else {
282 /* Return stub is in 32bit vsyscall page */
283 if (current->mm->context.vdso)
284 restorer = current->mm->context.vdso +
285 vdso_image_32.sym___kernel_sigreturn;
286 else
287 restorer = &frame->retcode;
288 }
289
290 if (!user_access_begin(frame, sizeof(*frame)))
291 return -EFAULT;
292
293 unsafe_put_user(ksig->sig, &frame->sig, Efault);
294 unsafe_put_sigcontext32(&frame->sc, fp, regs, set, Efault);
295 unsafe_put_user(set->sig[1], &frame->extramask[0], Efault);
296 unsafe_put_user(ptr_to_compat(restorer), &frame->pretcode, Efault);
297 /*
298 * These are actually not used anymore, but left because some
299 * gdb versions depend on them as a marker.
300 */
301 unsafe_put_user(*((u64 *)&code), (u64 __user *)frame->retcode, Efault);
302 user_access_end();
303
304 /* Set up registers for signal handler */
305 regs->sp = (unsigned long) frame;
306 regs->ip = (unsigned long) ksig->ka.sa.sa_handler;
307
308 /* Make -mregparm=3 work */
309 regs->ax = ksig->sig;
310 regs->dx = 0;
311 regs->cx = 0;
312
313 #ifdef CONFIG_IA32_EMULATION
314 loadsegment(ds, __USER_DS);
315 loadsegment(es, __USER_DS);
316 #else
317 regs->ds = __USER_DS;
318 regs->es = __USER_DS;
319 #endif
320
321 regs->cs = __USER32_CS;
322 regs->ss = __USER_DS;
323
324 return 0;
325 Efault:
326 user_access_end();
327 return -EFAULT;
328 }
329
ia32_setup_rt_frame(struct ksignal * ksig,struct pt_regs * regs)330 int ia32_setup_rt_frame(struct ksignal *ksig, struct pt_regs *regs)
331 {
332 sigset32_t *set = (sigset32_t *) sigmask_to_save();
333 struct rt_sigframe_ia32 __user *frame;
334 void __user *restorer;
335 void __user *fp = NULL;
336
337 /* unsafe_put_user optimizes that into a single 8 byte store */
338 static const struct {
339 u8 movl;
340 u32 val;
341 u16 int80;
342 u8 pad;
343 } __attribute__((packed)) code = {
344 0xb8,
345 __NR_ia32_rt_sigreturn,
346 0x80cd,
347 0,
348 };
349
350 frame = get_sigframe(ksig, regs, sizeof(*frame), &fp);
351
352 if (!user_access_begin(frame, sizeof(*frame)))
353 return -EFAULT;
354
355 unsafe_put_user(ksig->sig, &frame->sig, Efault);
356 unsafe_put_user(ptr_to_compat(&frame->info), &frame->pinfo, Efault);
357 unsafe_put_user(ptr_to_compat(&frame->uc), &frame->puc, Efault);
358
359 /* Create the ucontext. */
360 if (static_cpu_has(X86_FEATURE_XSAVE))
361 unsafe_put_user(UC_FP_XSTATE, &frame->uc.uc_flags, Efault);
362 else
363 unsafe_put_user(0, &frame->uc.uc_flags, Efault);
364 unsafe_put_user(0, &frame->uc.uc_link, Efault);
365 unsafe_save_altstack32(&frame->uc.uc_stack, regs->sp, Efault);
366
367 if (ksig->ka.sa.sa_flags & SA_RESTORER)
368 restorer = ksig->ka.sa.sa_restorer;
369 else
370 restorer = current->mm->context.vdso +
371 vdso_image_32.sym___kernel_rt_sigreturn;
372 unsafe_put_user(ptr_to_compat(restorer), &frame->pretcode, Efault);
373
374 /*
375 * Not actually used anymore, but left because some gdb
376 * versions need it.
377 */
378 unsafe_put_user(*((u64 *)&code), (u64 __user *)frame->retcode, Efault);
379 unsafe_put_sigcontext32(&frame->uc.uc_mcontext, fp, regs, set, Efault);
380 unsafe_put_user(*(__u64 *)set, (__u64 __user *)&frame->uc.uc_sigmask, Efault);
381 user_access_end();
382
383 if (__copy_siginfo_to_user32(&frame->info, &ksig->info))
384 return -EFAULT;
385
386 /* Set up registers for signal handler */
387 regs->sp = (unsigned long) frame;
388 regs->ip = (unsigned long) ksig->ka.sa.sa_handler;
389
390 /* Make -mregparm=3 work */
391 regs->ax = ksig->sig;
392 regs->dx = (unsigned long) &frame->info;
393 regs->cx = (unsigned long) &frame->uc;
394
395 #ifdef CONFIG_IA32_EMULATION
396 loadsegment(ds, __USER_DS);
397 loadsegment(es, __USER_DS);
398 #else
399 regs->ds = __USER_DS;
400 regs->es = __USER_DS;
401 #endif
402
403 regs->cs = __USER32_CS;
404 regs->ss = __USER_DS;
405
406 return 0;
407 Efault:
408 user_access_end();
409 return -EFAULT;
410 }
411
412 /*
413 * The siginfo_t structure and handing code is very easy
414 * to break in several ways. It must always be updated when new
415 * updates are made to the main siginfo_t, and
416 * copy_siginfo_to_user32() must be updated when the
417 * (arch-independent) copy_siginfo_to_user() is updated.
418 *
419 * It is also easy to put a new member in the siginfo_t
420 * which has implicit alignment which can move internal structure
421 * alignment around breaking the ABI. This can happen if you,
422 * for instance, put a plain 64-bit value in there.
423 */
424
425 /*
426 * If adding a new si_code, there is probably new data in
427 * the siginfo. Make sure folks bumping the si_code
428 * limits also have to look at this code. Make sure any
429 * new fields are handled in copy_siginfo_to_user32()!
430 */
431 static_assert(NSIGILL == 11);
432 static_assert(NSIGFPE == 15);
433 static_assert(NSIGSEGV == 10);
434 static_assert(NSIGBUS == 5);
435 static_assert(NSIGTRAP == 6);
436 static_assert(NSIGCHLD == 6);
437 static_assert(NSIGSYS == 2);
438
439 /* This is part of the ABI and can never change in size: */
440 static_assert(sizeof(siginfo32_t) == 128);
441
442 /* This is a part of the ABI and can never change in alignment */
443 static_assert(__alignof__(siginfo32_t) == 4);
444
445 /*
446 * The offsets of all the (unioned) si_fields are fixed
447 * in the ABI, of course. Make sure none of them ever
448 * move and are always at the beginning:
449 */
450 static_assert(offsetof(siginfo32_t, _sifields) == 3 * sizeof(int));
451
452 static_assert(offsetof(siginfo32_t, si_signo) == 0);
453 static_assert(offsetof(siginfo32_t, si_errno) == 4);
454 static_assert(offsetof(siginfo32_t, si_code) == 8);
455
456 /*
457 * Ensure that the size of each si_field never changes.
458 * If it does, it is a sign that the
459 * copy_siginfo_to_user32() code below needs to updated
460 * along with the size in the CHECK_SI_SIZE().
461 *
462 * We repeat this check for both the generic and compat
463 * siginfos.
464 *
465 * Note: it is OK for these to grow as long as the whole
466 * structure stays within the padding size (checked
467 * above).
468 */
469
470 #define CHECK_SI_OFFSET(name) \
471 static_assert(offsetof(siginfo32_t, _sifields) == \
472 offsetof(siginfo32_t, _sifields.name))
473
474 #define CHECK_SI_SIZE(name, size) \
475 static_assert(sizeof_field(siginfo32_t, _sifields.name) == size)
476
477 CHECK_SI_OFFSET(_kill);
478 CHECK_SI_SIZE (_kill, 2*sizeof(int));
479 static_assert(offsetof(siginfo32_t, si_pid) == 0xC);
480 static_assert(offsetof(siginfo32_t, si_uid) == 0x10);
481
482 CHECK_SI_OFFSET(_timer);
483 #ifdef CONFIG_COMPAT
484 /* compat_siginfo_t doesn't have si_sys_private */
485 CHECK_SI_SIZE (_timer, 3*sizeof(int));
486 #else
487 CHECK_SI_SIZE (_timer, 4*sizeof(int));
488 #endif
489 static_assert(offsetof(siginfo32_t, si_tid) == 0x0C);
490 static_assert(offsetof(siginfo32_t, si_overrun) == 0x10);
491 static_assert(offsetof(siginfo32_t, si_value) == 0x14);
492
493 CHECK_SI_OFFSET(_rt);
494 CHECK_SI_SIZE (_rt, 3*sizeof(int));
495 static_assert(offsetof(siginfo32_t, si_pid) == 0x0C);
496 static_assert(offsetof(siginfo32_t, si_uid) == 0x10);
497 static_assert(offsetof(siginfo32_t, si_value) == 0x14);
498
499 CHECK_SI_OFFSET(_sigchld);
500 CHECK_SI_SIZE (_sigchld, 5*sizeof(int));
501 static_assert(offsetof(siginfo32_t, si_pid) == 0x0C);
502 static_assert(offsetof(siginfo32_t, si_uid) == 0x10);
503 static_assert(offsetof(siginfo32_t, si_status) == 0x14);
504 static_assert(offsetof(siginfo32_t, si_utime) == 0x18);
505 static_assert(offsetof(siginfo32_t, si_stime) == 0x1C);
506
507 CHECK_SI_OFFSET(_sigfault);
508 CHECK_SI_SIZE (_sigfault, 4*sizeof(int));
509 static_assert(offsetof(siginfo32_t, si_addr) == 0x0C);
510
511 static_assert(offsetof(siginfo32_t, si_trapno) == 0x10);
512
513 static_assert(offsetof(siginfo32_t, si_addr_lsb) == 0x10);
514
515 static_assert(offsetof(siginfo32_t, si_lower) == 0x14);
516 static_assert(offsetof(siginfo32_t, si_upper) == 0x18);
517
518 static_assert(offsetof(siginfo32_t, si_pkey) == 0x14);
519
520 static_assert(offsetof(siginfo32_t, si_perf_data) == 0x10);
521 static_assert(offsetof(siginfo32_t, si_perf_type) == 0x14);
522 static_assert(offsetof(siginfo32_t, si_perf_flags) == 0x18);
523
524 CHECK_SI_OFFSET(_sigpoll);
525 CHECK_SI_SIZE (_sigpoll, 2*sizeof(int));
526 static_assert(offsetof(siginfo32_t, si_band) == 0x0C);
527 static_assert(offsetof(siginfo32_t, si_fd) == 0x10);
528
529 CHECK_SI_OFFSET(_sigsys);
530 CHECK_SI_SIZE (_sigsys, 3*sizeof(int));
531 static_assert(offsetof(siginfo32_t, si_call_addr) == 0x0C);
532 static_assert(offsetof(siginfo32_t, si_syscall) == 0x10);
533 static_assert(offsetof(siginfo32_t, si_arch) == 0x14);
534
535 /* any new si_fields should be added here */
536