1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Copyright (C) 1991, 1992 Linus Torvalds
4 * Copyright (C) 2000, 2001, 2002 Andi Kleen SuSE Labs
5 *
6 * 1997-11-28 Modified for POSIX.1b signals by Richard Henderson
7 * 2000-06-20 Pentium III FXSR, SSE support by Gareth Hughes
8 * 2000-2002 x86-64 support by Andi Kleen
9 */
10
11 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
12
13 #include <linux/sched.h>
14 #include <linux/sched/task_stack.h>
15 #include <linux/mm.h>
16 #include <linux/smp.h>
17 #include <linux/kernel.h>
18 #include <linux/kstrtox.h>
19 #include <linux/errno.h>
20 #include <linux/wait.h>
21 #include <linux/tracehook.h>
22 #include <linux/unistd.h>
23 #include <linux/stddef.h>
24 #include <linux/personality.h>
25 #include <linux/uaccess.h>
26 #include <linux/user-return-notifier.h>
27 #include <linux/uprobes.h>
28 #include <linux/context_tracking.h>
29 #include <linux/entry-common.h>
30 #include <linux/syscalls.h>
31
32 #include <asm/processor.h>
33 #include <asm/ucontext.h>
34 #include <asm/fpu/signal.h>
35 #include <asm/fpu/xstate.h>
36 #include <asm/vdso.h>
37 #include <asm/mce.h>
38 #include <asm/sighandling.h>
39 #include <asm/vm86.h>
40
41 #ifdef CONFIG_X86_64
42 #include <linux/compat.h>
43 #include <asm/proto.h>
44 #include <asm/ia32_unistd.h>
45 #include <asm/fpu/xstate.h>
46 #endif /* CONFIG_X86_64 */
47
48 #include <asm/syscall.h>
49 #include <asm/sigframe.h>
50 #include <asm/signal.h>
51
52 #ifdef CONFIG_X86_64
53 /*
54 * If regs->ss will cause an IRET fault, change it. Otherwise leave it
55 * alone. Using this generally makes no sense unless
56 * user_64bit_mode(regs) would return true.
57 */
force_valid_ss(struct pt_regs * regs)58 static void force_valid_ss(struct pt_regs *regs)
59 {
60 u32 ar;
61 asm volatile ("lar %[old_ss], %[ar]\n\t"
62 "jz 1f\n\t" /* If invalid: */
63 "xorl %[ar], %[ar]\n\t" /* set ar = 0 */
64 "1:"
65 : [ar] "=r" (ar)
66 : [old_ss] "rm" ((u16)regs->ss));
67
68 /*
69 * For a valid 64-bit user context, we need DPL 3, type
70 * read-write data or read-write exp-down data, and S and P
71 * set. We can't use VERW because VERW doesn't check the
72 * P bit.
73 */
74 ar &= AR_DPL_MASK | AR_S | AR_P | AR_TYPE_MASK;
75 if (ar != (AR_DPL3 | AR_S | AR_P | AR_TYPE_RWDATA) &&
76 ar != (AR_DPL3 | AR_S | AR_P | AR_TYPE_RWDATA_EXPDOWN))
77 regs->ss = __USER_DS;
78 }
79 # define CONTEXT_COPY_SIZE offsetof(struct sigcontext, reserved1)
80 #else
81 # define CONTEXT_COPY_SIZE sizeof(struct sigcontext)
82 #endif
83
restore_sigcontext(struct pt_regs * regs,struct sigcontext __user * usc,unsigned long uc_flags)84 static bool restore_sigcontext(struct pt_regs *regs,
85 struct sigcontext __user *usc,
86 unsigned long uc_flags)
87 {
88 struct sigcontext sc;
89
90 /* Always make any pending restarted system calls return -EINTR */
91 current->restart_block.fn = do_no_restart_syscall;
92
93 if (copy_from_user(&sc, usc, CONTEXT_COPY_SIZE))
94 return false;
95
96 #ifdef CONFIG_X86_32
97 set_user_gs(regs, sc.gs);
98 regs->fs = sc.fs;
99 regs->es = sc.es;
100 regs->ds = sc.ds;
101 #endif /* CONFIG_X86_32 */
102
103 regs->bx = sc.bx;
104 regs->cx = sc.cx;
105 regs->dx = sc.dx;
106 regs->si = sc.si;
107 regs->di = sc.di;
108 regs->bp = sc.bp;
109 regs->ax = sc.ax;
110 regs->sp = sc.sp;
111 regs->ip = sc.ip;
112
113 #ifdef CONFIG_X86_64
114 regs->r8 = sc.r8;
115 regs->r9 = sc.r9;
116 regs->r10 = sc.r10;
117 regs->r11 = sc.r11;
118 regs->r12 = sc.r12;
119 regs->r13 = sc.r13;
120 regs->r14 = sc.r14;
121 regs->r15 = sc.r15;
122 #endif /* CONFIG_X86_64 */
123
124 /* Get CS/SS and force CPL3 */
125 regs->cs = sc.cs | 0x03;
126 regs->ss = sc.ss | 0x03;
127
128 regs->flags = (regs->flags & ~FIX_EFLAGS) | (sc.flags & FIX_EFLAGS);
129 /* disable syscall checks */
130 regs->orig_ax = -1;
131
132 #ifdef CONFIG_X86_64
133 /*
134 * Fix up SS if needed for the benefit of old DOSEMU and
135 * CRIU.
136 */
137 if (unlikely(!(uc_flags & UC_STRICT_RESTORE_SS) && user_64bit_mode(regs)))
138 force_valid_ss(regs);
139 #endif
140
141 return fpu__restore_sig((void __user *)sc.fpstate,
142 IS_ENABLED(CONFIG_X86_32));
143 }
144
145 static __always_inline int
__unsafe_setup_sigcontext(struct sigcontext __user * sc,void __user * fpstate,struct pt_regs * regs,unsigned long mask)146 __unsafe_setup_sigcontext(struct sigcontext __user *sc, void __user *fpstate,
147 struct pt_regs *regs, unsigned long mask)
148 {
149 #ifdef CONFIG_X86_32
150 unsafe_put_user(get_user_gs(regs),
151 (unsigned int __user *)&sc->gs, Efault);
152 unsafe_put_user(regs->fs, (unsigned int __user *)&sc->fs, Efault);
153 unsafe_put_user(regs->es, (unsigned int __user *)&sc->es, Efault);
154 unsafe_put_user(regs->ds, (unsigned int __user *)&sc->ds, Efault);
155 #endif /* CONFIG_X86_32 */
156
157 unsafe_put_user(regs->di, &sc->di, Efault);
158 unsafe_put_user(regs->si, &sc->si, Efault);
159 unsafe_put_user(regs->bp, &sc->bp, Efault);
160 unsafe_put_user(regs->sp, &sc->sp, Efault);
161 unsafe_put_user(regs->bx, &sc->bx, Efault);
162 unsafe_put_user(regs->dx, &sc->dx, Efault);
163 unsafe_put_user(regs->cx, &sc->cx, Efault);
164 unsafe_put_user(regs->ax, &sc->ax, Efault);
165 #ifdef CONFIG_X86_64
166 unsafe_put_user(regs->r8, &sc->r8, Efault);
167 unsafe_put_user(regs->r9, &sc->r9, Efault);
168 unsafe_put_user(regs->r10, &sc->r10, Efault);
169 unsafe_put_user(regs->r11, &sc->r11, Efault);
170 unsafe_put_user(regs->r12, &sc->r12, Efault);
171 unsafe_put_user(regs->r13, &sc->r13, Efault);
172 unsafe_put_user(regs->r14, &sc->r14, Efault);
173 unsafe_put_user(regs->r15, &sc->r15, Efault);
174 #endif /* CONFIG_X86_64 */
175
176 unsafe_put_user(current->thread.trap_nr, &sc->trapno, Efault);
177 unsafe_put_user(current->thread.error_code, &sc->err, Efault);
178 unsafe_put_user(regs->ip, &sc->ip, Efault);
179 #ifdef CONFIG_X86_32
180 unsafe_put_user(regs->cs, (unsigned int __user *)&sc->cs, Efault);
181 unsafe_put_user(regs->flags, &sc->flags, Efault);
182 unsafe_put_user(regs->sp, &sc->sp_at_signal, Efault);
183 unsafe_put_user(regs->ss, (unsigned int __user *)&sc->ss, Efault);
184 #else /* !CONFIG_X86_32 */
185 unsafe_put_user(regs->flags, &sc->flags, Efault);
186 unsafe_put_user(regs->cs, &sc->cs, Efault);
187 unsafe_put_user(0, &sc->gs, Efault);
188 unsafe_put_user(0, &sc->fs, Efault);
189 unsafe_put_user(regs->ss, &sc->ss, Efault);
190 #endif /* CONFIG_X86_32 */
191
192 unsafe_put_user(fpstate, (unsigned long __user *)&sc->fpstate, Efault);
193
194 /* non-iBCS2 extensions.. */
195 unsafe_put_user(mask, &sc->oldmask, Efault);
196 unsafe_put_user(current->thread.cr2, &sc->cr2, Efault);
197 return 0;
198 Efault:
199 return -EFAULT;
200 }
201
202 #define unsafe_put_sigcontext(sc, fp, regs, set, label) \
203 do { \
204 if (__unsafe_setup_sigcontext(sc, fp, regs, set->sig[0])) \
205 goto label; \
206 } while(0);
207
208 #define unsafe_put_sigmask(set, frame, label) \
209 unsafe_put_user(*(__u64 *)(set), \
210 (__u64 __user *)&(frame)->uc.uc_sigmask, \
211 label)
212
213 /*
214 * Set up a signal frame.
215 */
216
217 /* x86 ABI requires 16-byte alignment */
218 #define FRAME_ALIGNMENT 16UL
219
220 #define MAX_FRAME_PADDING (FRAME_ALIGNMENT - 1)
221
222 /*
223 * Determine which stack to use..
224 */
align_sigframe(unsigned long sp)225 static unsigned long align_sigframe(unsigned long sp)
226 {
227 #ifdef CONFIG_X86_32
228 /*
229 * Align the stack pointer according to the i386 ABI,
230 * i.e. so that on function entry ((sp + 4) & 15) == 0.
231 */
232 sp = ((sp + 4) & -FRAME_ALIGNMENT) - 4;
233 #else /* !CONFIG_X86_32 */
234 sp = round_down(sp, FRAME_ALIGNMENT) - 8;
235 #endif
236 return sp;
237 }
238
239 static void __user *
get_sigframe(struct k_sigaction * ka,struct pt_regs * regs,size_t frame_size,void __user ** fpstate)240 get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t frame_size,
241 void __user **fpstate)
242 {
243 /* Default to using normal stack */
244 bool nested_altstack = on_sig_stack(regs->sp);
245 bool entering_altstack = false;
246 unsigned long math_size = 0;
247 unsigned long sp = regs->sp;
248 unsigned long buf_fx = 0;
249
250 /* redzone */
251 if (IS_ENABLED(CONFIG_X86_64))
252 sp -= 128;
253
254 /* This is the X/Open sanctioned signal stack switching. */
255 if (ka->sa.sa_flags & SA_ONSTACK) {
256 /*
257 * This checks nested_altstack via sas_ss_flags(). Sensible
258 * programs use SS_AUTODISARM, which disables that check, and
259 * programs that don't use SS_AUTODISARM get compatible.
260 */
261 if (sas_ss_flags(sp) == 0) {
262 sp = current->sas_ss_sp + current->sas_ss_size;
263 entering_altstack = true;
264 }
265 } else if (IS_ENABLED(CONFIG_X86_32) &&
266 !nested_altstack &&
267 regs->ss != __USER_DS &&
268 !(ka->sa.sa_flags & SA_RESTORER) &&
269 ka->sa.sa_restorer) {
270 /* This is the legacy signal stack switching. */
271 sp = (unsigned long) ka->sa.sa_restorer;
272 entering_altstack = true;
273 }
274
275 sp = fpu__alloc_mathframe(sp, IS_ENABLED(CONFIG_X86_32),
276 &buf_fx, &math_size);
277 *fpstate = (void __user *)sp;
278
279 sp = align_sigframe(sp - frame_size);
280
281 /*
282 * If we are on the alternate signal stack and would overflow it, don't.
283 * Return an always-bogus address instead so we will die with SIGSEGV.
284 */
285 if (unlikely((nested_altstack || entering_altstack) &&
286 !__on_sig_stack(sp))) {
287
288 if (show_unhandled_signals && printk_ratelimit())
289 pr_info("%s[%d] overflowed sigaltstack\n",
290 current->comm, task_pid_nr(current));
291
292 return (void __user *)-1L;
293 }
294
295 /* save i387 and extended state */
296 if (!copy_fpstate_to_sigframe(*fpstate, (void __user *)buf_fx, math_size))
297 return (void __user *)-1L;
298
299 return (void __user *)sp;
300 }
301
302 #ifdef CONFIG_X86_32
303 static const struct {
304 u16 poplmovl;
305 u32 val;
306 u16 int80;
307 } __attribute__((packed)) retcode = {
308 0xb858, /* popl %eax; movl $..., %eax */
309 __NR_sigreturn,
310 0x80cd, /* int $0x80 */
311 };
312
313 static const struct {
314 u8 movl;
315 u32 val;
316 u16 int80;
317 u8 pad;
318 } __attribute__((packed)) rt_retcode = {
319 0xb8, /* movl $..., %eax */
320 __NR_rt_sigreturn,
321 0x80cd, /* int $0x80 */
322 0
323 };
324
325 static int
__setup_frame(int sig,struct ksignal * ksig,sigset_t * set,struct pt_regs * regs)326 __setup_frame(int sig, struct ksignal *ksig, sigset_t *set,
327 struct pt_regs *regs)
328 {
329 struct sigframe __user *frame;
330 void __user *restorer;
331 void __user *fp = NULL;
332
333 frame = get_sigframe(&ksig->ka, regs, sizeof(*frame), &fp);
334
335 if (!user_access_begin(frame, sizeof(*frame)))
336 return -EFAULT;
337
338 unsafe_put_user(sig, &frame->sig, Efault);
339 unsafe_put_sigcontext(&frame->sc, fp, regs, set, Efault);
340 unsafe_put_user(set->sig[1], &frame->extramask[0], Efault);
341 if (current->mm->context.vdso)
342 restorer = current->mm->context.vdso +
343 vdso_image_32.sym___kernel_sigreturn;
344 else
345 restorer = &frame->retcode;
346 if (ksig->ka.sa.sa_flags & SA_RESTORER)
347 restorer = ksig->ka.sa.sa_restorer;
348
349 /* Set up to return from userspace. */
350 unsafe_put_user(restorer, &frame->pretcode, Efault);
351
352 /*
353 * This is popl %eax ; movl $__NR_sigreturn, %eax ; int $0x80
354 *
355 * WE DO NOT USE IT ANY MORE! It's only left here for historical
356 * reasons and because gdb uses it as a signature to notice
357 * signal handler stack frames.
358 */
359 unsafe_put_user(*((u64 *)&retcode), (u64 *)frame->retcode, Efault);
360 user_access_end();
361
362 /* Set up registers for signal handler */
363 regs->sp = (unsigned long)frame;
364 regs->ip = (unsigned long)ksig->ka.sa.sa_handler;
365 regs->ax = (unsigned long)sig;
366 regs->dx = 0;
367 regs->cx = 0;
368
369 regs->ds = __USER_DS;
370 regs->es = __USER_DS;
371 regs->ss = __USER_DS;
372 regs->cs = __USER_CS;
373
374 return 0;
375
376 Efault:
377 user_access_end();
378 return -EFAULT;
379 }
380
__setup_rt_frame(int sig,struct ksignal * ksig,sigset_t * set,struct pt_regs * regs)381 static int __setup_rt_frame(int sig, struct ksignal *ksig,
382 sigset_t *set, struct pt_regs *regs)
383 {
384 struct rt_sigframe __user *frame;
385 void __user *restorer;
386 void __user *fp = NULL;
387
388 frame = get_sigframe(&ksig->ka, regs, sizeof(*frame), &fp);
389
390 if (!user_access_begin(frame, sizeof(*frame)))
391 return -EFAULT;
392
393 unsafe_put_user(sig, &frame->sig, Efault);
394 unsafe_put_user(&frame->info, &frame->pinfo, Efault);
395 unsafe_put_user(&frame->uc, &frame->puc, Efault);
396
397 /* Create the ucontext. */
398 if (static_cpu_has(X86_FEATURE_XSAVE))
399 unsafe_put_user(UC_FP_XSTATE, &frame->uc.uc_flags, Efault);
400 else
401 unsafe_put_user(0, &frame->uc.uc_flags, Efault);
402 unsafe_put_user(0, &frame->uc.uc_link, Efault);
403 unsafe_save_altstack(&frame->uc.uc_stack, regs->sp, Efault);
404
405 /* Set up to return from userspace. */
406 restorer = current->mm->context.vdso +
407 vdso_image_32.sym___kernel_rt_sigreturn;
408 if (ksig->ka.sa.sa_flags & SA_RESTORER)
409 restorer = ksig->ka.sa.sa_restorer;
410 unsafe_put_user(restorer, &frame->pretcode, Efault);
411
412 /*
413 * This is movl $__NR_rt_sigreturn, %ax ; int $0x80
414 *
415 * WE DO NOT USE IT ANY MORE! It's only left here for historical
416 * reasons and because gdb uses it as a signature to notice
417 * signal handler stack frames.
418 */
419 unsafe_put_user(*((u64 *)&rt_retcode), (u64 *)frame->retcode, Efault);
420 unsafe_put_sigcontext(&frame->uc.uc_mcontext, fp, regs, set, Efault);
421 unsafe_put_sigmask(set, frame, Efault);
422 user_access_end();
423
424 if (copy_siginfo_to_user(&frame->info, &ksig->info))
425 return -EFAULT;
426
427 /* Set up registers for signal handler */
428 regs->sp = (unsigned long)frame;
429 regs->ip = (unsigned long)ksig->ka.sa.sa_handler;
430 regs->ax = (unsigned long)sig;
431 regs->dx = (unsigned long)&frame->info;
432 regs->cx = (unsigned long)&frame->uc;
433
434 regs->ds = __USER_DS;
435 regs->es = __USER_DS;
436 regs->ss = __USER_DS;
437 regs->cs = __USER_CS;
438
439 return 0;
440 Efault:
441 user_access_end();
442 return -EFAULT;
443 }
444 #else /* !CONFIG_X86_32 */
frame_uc_flags(struct pt_regs * regs)445 static unsigned long frame_uc_flags(struct pt_regs *regs)
446 {
447 unsigned long flags;
448
449 if (boot_cpu_has(X86_FEATURE_XSAVE))
450 flags = UC_FP_XSTATE | UC_SIGCONTEXT_SS;
451 else
452 flags = UC_SIGCONTEXT_SS;
453
454 if (likely(user_64bit_mode(regs)))
455 flags |= UC_STRICT_RESTORE_SS;
456
457 return flags;
458 }
459
__setup_rt_frame(int sig,struct ksignal * ksig,sigset_t * set,struct pt_regs * regs)460 static int __setup_rt_frame(int sig, struct ksignal *ksig,
461 sigset_t *set, struct pt_regs *regs)
462 {
463 struct rt_sigframe __user *frame;
464 void __user *fp = NULL;
465 unsigned long uc_flags;
466
467 /* x86-64 should always use SA_RESTORER. */
468 if (!(ksig->ka.sa.sa_flags & SA_RESTORER))
469 return -EFAULT;
470
471 frame = get_sigframe(&ksig->ka, regs, sizeof(struct rt_sigframe), &fp);
472 uc_flags = frame_uc_flags(regs);
473
474 if (!user_access_begin(frame, sizeof(*frame)))
475 return -EFAULT;
476
477 /* Create the ucontext. */
478 unsafe_put_user(uc_flags, &frame->uc.uc_flags, Efault);
479 unsafe_put_user(0, &frame->uc.uc_link, Efault);
480 unsafe_save_altstack(&frame->uc.uc_stack, regs->sp, Efault);
481
482 /* Set up to return from userspace. If provided, use a stub
483 already in userspace. */
484 unsafe_put_user(ksig->ka.sa.sa_restorer, &frame->pretcode, Efault);
485 unsafe_put_sigcontext(&frame->uc.uc_mcontext, fp, regs, set, Efault);
486 unsafe_put_sigmask(set, frame, Efault);
487 user_access_end();
488
489 if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
490 if (copy_siginfo_to_user(&frame->info, &ksig->info))
491 return -EFAULT;
492 }
493
494 /* Set up registers for signal handler */
495 regs->di = sig;
496 /* In case the signal handler was declared without prototypes */
497 regs->ax = 0;
498
499 /* This also works for non SA_SIGINFO handlers because they expect the
500 next argument after the signal number on the stack. */
501 regs->si = (unsigned long)&frame->info;
502 regs->dx = (unsigned long)&frame->uc;
503 regs->ip = (unsigned long) ksig->ka.sa.sa_handler;
504
505 regs->sp = (unsigned long)frame;
506
507 /*
508 * Set up the CS and SS registers to run signal handlers in
509 * 64-bit mode, even if the handler happens to be interrupting
510 * 32-bit or 16-bit code.
511 *
512 * SS is subtle. In 64-bit mode, we don't need any particular
513 * SS descriptor, but we do need SS to be valid. It's possible
514 * that the old SS is entirely bogus -- this can happen if the
515 * signal we're trying to deliver is #GP or #SS caused by a bad
516 * SS value. We also have a compatibility issue here: DOSEMU
517 * relies on the contents of the SS register indicating the
518 * SS value at the time of the signal, even though that code in
519 * DOSEMU predates sigreturn's ability to restore SS. (DOSEMU
520 * avoids relying on sigreturn to restore SS; instead it uses
521 * a trampoline.) So we do our best: if the old SS was valid,
522 * we keep it. Otherwise we replace it.
523 */
524 regs->cs = __USER_CS;
525
526 if (unlikely(regs->ss != __USER_DS))
527 force_valid_ss(regs);
528
529 return 0;
530
531 Efault:
532 user_access_end();
533 return -EFAULT;
534 }
535 #endif /* CONFIG_X86_32 */
536
537 #ifdef CONFIG_X86_X32_ABI
x32_copy_siginfo_to_user(struct compat_siginfo __user * to,const struct kernel_siginfo * from)538 static int x32_copy_siginfo_to_user(struct compat_siginfo __user *to,
539 const struct kernel_siginfo *from)
540 {
541 struct compat_siginfo new;
542
543 copy_siginfo_to_external32(&new, from);
544 if (from->si_signo == SIGCHLD) {
545 new._sifields._sigchld_x32._utime = from->si_utime;
546 new._sifields._sigchld_x32._stime = from->si_stime;
547 }
548 if (copy_to_user(to, &new, sizeof(struct compat_siginfo)))
549 return -EFAULT;
550 return 0;
551 }
552
copy_siginfo_to_user32(struct compat_siginfo __user * to,const struct kernel_siginfo * from)553 int copy_siginfo_to_user32(struct compat_siginfo __user *to,
554 const struct kernel_siginfo *from)
555 {
556 if (in_x32_syscall())
557 return x32_copy_siginfo_to_user(to, from);
558 return __copy_siginfo_to_user32(to, from);
559 }
560 #endif /* CONFIG_X86_X32_ABI */
561
x32_setup_rt_frame(struct ksignal * ksig,compat_sigset_t * set,struct pt_regs * regs)562 static int x32_setup_rt_frame(struct ksignal *ksig,
563 compat_sigset_t *set,
564 struct pt_regs *regs)
565 {
566 #ifdef CONFIG_X86_X32_ABI
567 struct rt_sigframe_x32 __user *frame;
568 unsigned long uc_flags;
569 void __user *restorer;
570 void __user *fp = NULL;
571
572 if (!(ksig->ka.sa.sa_flags & SA_RESTORER))
573 return -EFAULT;
574
575 frame = get_sigframe(&ksig->ka, regs, sizeof(*frame), &fp);
576
577 uc_flags = frame_uc_flags(regs);
578
579 if (!user_access_begin(frame, sizeof(*frame)))
580 return -EFAULT;
581
582 /* Create the ucontext. */
583 unsafe_put_user(uc_flags, &frame->uc.uc_flags, Efault);
584 unsafe_put_user(0, &frame->uc.uc_link, Efault);
585 unsafe_compat_save_altstack(&frame->uc.uc_stack, regs->sp, Efault);
586 unsafe_put_user(0, &frame->uc.uc__pad0, Efault);
587 restorer = ksig->ka.sa.sa_restorer;
588 unsafe_put_user(restorer, (unsigned long __user *)&frame->pretcode, Efault);
589 unsafe_put_sigcontext(&frame->uc.uc_mcontext, fp, regs, set, Efault);
590 unsafe_put_sigmask(set, frame, Efault);
591 user_access_end();
592
593 if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
594 if (x32_copy_siginfo_to_user(&frame->info, &ksig->info))
595 return -EFAULT;
596 }
597
598 /* Set up registers for signal handler */
599 regs->sp = (unsigned long) frame;
600 regs->ip = (unsigned long) ksig->ka.sa.sa_handler;
601
602 /* We use the x32 calling convention here... */
603 regs->di = ksig->sig;
604 regs->si = (unsigned long) &frame->info;
605 regs->dx = (unsigned long) &frame->uc;
606
607 loadsegment(ds, __USER_DS);
608 loadsegment(es, __USER_DS);
609
610 regs->cs = __USER_CS;
611 regs->ss = __USER_DS;
612 #endif /* CONFIG_X86_X32_ABI */
613
614 return 0;
615 #ifdef CONFIG_X86_X32_ABI
616 Efault:
617 user_access_end();
618 return -EFAULT;
619 #endif
620 }
621
622 /*
623 * Do a signal return; undo the signal stack.
624 */
625 #ifdef CONFIG_X86_32
SYSCALL_DEFINE0(sigreturn)626 SYSCALL_DEFINE0(sigreturn)
627 {
628 struct pt_regs *regs = current_pt_regs();
629 struct sigframe __user *frame;
630 sigset_t set;
631
632 frame = (struct sigframe __user *)(regs->sp - 8);
633
634 if (!access_ok(frame, sizeof(*frame)))
635 goto badframe;
636 if (__get_user(set.sig[0], &frame->sc.oldmask) ||
637 __get_user(set.sig[1], &frame->extramask[0]))
638 goto badframe;
639
640 set_current_blocked(&set);
641
642 /*
643 * x86_32 has no uc_flags bits relevant to restore_sigcontext.
644 * Save a few cycles by skipping the __get_user.
645 */
646 if (!restore_sigcontext(regs, &frame->sc, 0))
647 goto badframe;
648 return regs->ax;
649
650 badframe:
651 signal_fault(regs, frame, "sigreturn");
652
653 return 0;
654 }
655 #endif /* CONFIG_X86_32 */
656
SYSCALL_DEFINE0(rt_sigreturn)657 SYSCALL_DEFINE0(rt_sigreturn)
658 {
659 struct pt_regs *regs = current_pt_regs();
660 struct rt_sigframe __user *frame;
661 sigset_t set;
662 unsigned long uc_flags;
663
664 frame = (struct rt_sigframe __user *)(regs->sp - sizeof(long));
665 if (!access_ok(frame, sizeof(*frame)))
666 goto badframe;
667 if (__get_user(*(__u64 *)&set, (__u64 __user *)&frame->uc.uc_sigmask))
668 goto badframe;
669 if (__get_user(uc_flags, &frame->uc.uc_flags))
670 goto badframe;
671
672 set_current_blocked(&set);
673
674 if (!restore_sigcontext(regs, &frame->uc.uc_mcontext, uc_flags))
675 goto badframe;
676
677 if (restore_altstack(&frame->uc.uc_stack))
678 goto badframe;
679
680 return regs->ax;
681
682 badframe:
683 signal_fault(regs, frame, "rt_sigreturn");
684 return 0;
685 }
686
687 /*
688 * There are four different struct types for signal frame: sigframe_ia32,
689 * rt_sigframe_ia32, rt_sigframe_x32, and rt_sigframe. Use the worst case
690 * -- the largest size. It means the size for 64-bit apps is a bit more
691 * than needed, but this keeps the code simple.
692 */
693 #if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION)
694 # define MAX_FRAME_SIGINFO_UCTXT_SIZE sizeof(struct sigframe_ia32)
695 #else
696 # define MAX_FRAME_SIGINFO_UCTXT_SIZE sizeof(struct rt_sigframe)
697 #endif
698
699 /*
700 * The FP state frame contains an XSAVE buffer which must be 64-byte aligned.
701 * If a signal frame starts at an unaligned address, extra space is required.
702 * This is the max alignment padding, conservatively.
703 */
704 #define MAX_XSAVE_PADDING 63UL
705
706 /*
707 * The frame data is composed of the following areas and laid out as:
708 *
709 * -------------------------
710 * | alignment padding |
711 * -------------------------
712 * | (f)xsave frame |
713 * -------------------------
714 * | fsave header |
715 * -------------------------
716 * | alignment padding |
717 * -------------------------
718 * | siginfo + ucontext |
719 * -------------------------
720 */
721
722 /* max_frame_size tells userspace the worst case signal stack size. */
723 static unsigned long __ro_after_init max_frame_size;
724 static unsigned int __ro_after_init fpu_default_state_size;
725
init_sigframe_size(void)726 void __init init_sigframe_size(void)
727 {
728 fpu_default_state_size = fpu__get_fpstate_size();
729
730 max_frame_size = MAX_FRAME_SIGINFO_UCTXT_SIZE + MAX_FRAME_PADDING;
731
732 max_frame_size += fpu_default_state_size + MAX_XSAVE_PADDING;
733
734 /* Userspace expects an aligned size. */
735 max_frame_size = round_up(max_frame_size, FRAME_ALIGNMENT);
736
737 pr_info("max sigframe size: %lu\n", max_frame_size);
738 }
739
get_sigframe_size(void)740 unsigned long get_sigframe_size(void)
741 {
742 return max_frame_size;
743 }
744
is_ia32_compat_frame(struct ksignal * ksig)745 static inline int is_ia32_compat_frame(struct ksignal *ksig)
746 {
747 return IS_ENABLED(CONFIG_IA32_EMULATION) &&
748 ksig->ka.sa.sa_flags & SA_IA32_ABI;
749 }
750
is_ia32_frame(struct ksignal * ksig)751 static inline int is_ia32_frame(struct ksignal *ksig)
752 {
753 return IS_ENABLED(CONFIG_X86_32) || is_ia32_compat_frame(ksig);
754 }
755
is_x32_frame(struct ksignal * ksig)756 static inline int is_x32_frame(struct ksignal *ksig)
757 {
758 return IS_ENABLED(CONFIG_X86_X32_ABI) &&
759 ksig->ka.sa.sa_flags & SA_X32_ABI;
760 }
761
762 static int
setup_rt_frame(struct ksignal * ksig,struct pt_regs * regs)763 setup_rt_frame(struct ksignal *ksig, struct pt_regs *regs)
764 {
765 int usig = ksig->sig;
766 sigset_t *set = sigmask_to_save();
767 compat_sigset_t *cset = (compat_sigset_t *) set;
768
769 /* Perform fixup for the pre-signal frame. */
770 rseq_signal_deliver(ksig, regs);
771
772 /* Set up the stack frame */
773 if (is_ia32_frame(ksig)) {
774 if (ksig->ka.sa.sa_flags & SA_SIGINFO)
775 return ia32_setup_rt_frame(usig, ksig, cset, regs);
776 else
777 return ia32_setup_frame(usig, ksig, cset, regs);
778 } else if (is_x32_frame(ksig)) {
779 return x32_setup_rt_frame(ksig, cset, regs);
780 } else {
781 return __setup_rt_frame(ksig->sig, ksig, set, regs);
782 }
783 }
784
785 static void
handle_signal(struct ksignal * ksig,struct pt_regs * regs)786 handle_signal(struct ksignal *ksig, struct pt_regs *regs)
787 {
788 bool stepping, failed;
789 struct fpu *fpu = ¤t->thread.fpu;
790
791 if (v8086_mode(regs))
792 save_v86_state((struct kernel_vm86_regs *) regs, VM86_SIGNAL);
793
794 /* Are we from a system call? */
795 if (syscall_get_nr(current, regs) != -1) {
796 /* If so, check system call restarting.. */
797 switch (syscall_get_error(current, regs)) {
798 case -ERESTART_RESTARTBLOCK:
799 case -ERESTARTNOHAND:
800 regs->ax = -EINTR;
801 break;
802
803 case -ERESTARTSYS:
804 if (!(ksig->ka.sa.sa_flags & SA_RESTART)) {
805 regs->ax = -EINTR;
806 break;
807 }
808 fallthrough;
809 case -ERESTARTNOINTR:
810 regs->ax = regs->orig_ax;
811 regs->ip -= 2;
812 break;
813 }
814 }
815
816 /*
817 * If TF is set due to a debugger (TIF_FORCED_TF), clear TF now
818 * so that register information in the sigcontext is correct and
819 * then notify the tracer before entering the signal handler.
820 */
821 stepping = test_thread_flag(TIF_SINGLESTEP);
822 if (stepping)
823 user_disable_single_step(current);
824
825 failed = (setup_rt_frame(ksig, regs) < 0);
826 if (!failed) {
827 /*
828 * Clear the direction flag as per the ABI for function entry.
829 *
830 * Clear RF when entering the signal handler, because
831 * it might disable possible debug exception from the
832 * signal handler.
833 *
834 * Clear TF for the case when it wasn't set by debugger to
835 * avoid the recursive send_sigtrap() in SIGTRAP handler.
836 */
837 regs->flags &= ~(X86_EFLAGS_DF|X86_EFLAGS_RF|X86_EFLAGS_TF);
838 /*
839 * Ensure the signal handler starts with the new fpu state.
840 */
841 fpu__clear_user_states(fpu);
842 }
843 signal_setup_done(failed, ksig, stepping);
844 }
845
get_nr_restart_syscall(const struct pt_regs * regs)846 static inline unsigned long get_nr_restart_syscall(const struct pt_regs *regs)
847 {
848 #ifdef CONFIG_IA32_EMULATION
849 if (current->restart_block.arch_data & TS_COMPAT)
850 return __NR_ia32_restart_syscall;
851 #endif
852 #ifdef CONFIG_X86_X32_ABI
853 return __NR_restart_syscall | (regs->orig_ax & __X32_SYSCALL_BIT);
854 #else
855 return __NR_restart_syscall;
856 #endif
857 }
858
859 /*
860 * Note that 'init' is a special process: it doesn't get signals it doesn't
861 * want to handle. Thus you cannot kill init even with a SIGKILL even by
862 * mistake.
863 */
arch_do_signal_or_restart(struct pt_regs * regs,bool has_signal)864 void arch_do_signal_or_restart(struct pt_regs *regs, bool has_signal)
865 {
866 struct ksignal ksig;
867
868 if (has_signal && get_signal(&ksig)) {
869 /* Whee! Actually deliver the signal. */
870 handle_signal(&ksig, regs);
871 return;
872 }
873
874 /* Did we come from a system call? */
875 if (syscall_get_nr(current, regs) != -1) {
876 /* Restart the system call - no handlers present */
877 switch (syscall_get_error(current, regs)) {
878 case -ERESTARTNOHAND:
879 case -ERESTARTSYS:
880 case -ERESTARTNOINTR:
881 regs->ax = regs->orig_ax;
882 regs->ip -= 2;
883 break;
884
885 case -ERESTART_RESTARTBLOCK:
886 regs->ax = get_nr_restart_syscall(regs);
887 regs->ip -= 2;
888 break;
889 }
890 }
891
892 /*
893 * If there's no signal to deliver, we just put the saved sigmask
894 * back.
895 */
896 restore_saved_sigmask();
897 }
898
signal_fault(struct pt_regs * regs,void __user * frame,char * where)899 void signal_fault(struct pt_regs *regs, void __user *frame, char *where)
900 {
901 struct task_struct *me = current;
902
903 if (show_unhandled_signals && printk_ratelimit()) {
904 printk("%s"
905 "%s[%d] bad frame in %s frame:%p ip:%lx sp:%lx orax:%lx",
906 task_pid_nr(current) > 1 ? KERN_INFO : KERN_EMERG,
907 me->comm, me->pid, where, frame,
908 regs->ip, regs->sp, regs->orig_ax);
909 print_vma_addr(KERN_CONT " in ", regs->ip);
910 pr_cont("\n");
911 }
912
913 force_sig(SIGSEGV);
914 }
915
916 #ifdef CONFIG_DYNAMIC_SIGFRAME
917 #ifdef CONFIG_STRICT_SIGALTSTACK_SIZE
918 static bool strict_sigaltstack_size __ro_after_init = true;
919 #else
920 static bool strict_sigaltstack_size __ro_after_init = false;
921 #endif
922
strict_sas_size(char * arg)923 static int __init strict_sas_size(char *arg)
924 {
925 return kstrtobool(arg, &strict_sigaltstack_size);
926 }
927 __setup("strict_sas_size", strict_sas_size);
928
929 /*
930 * MINSIGSTKSZ is 2048 and can't be changed despite the fact that AVX512
931 * exceeds that size already. As such programs might never use the
932 * sigaltstack they just continued to work. While always checking against
933 * the real size would be correct, this might be considered a regression.
934 *
935 * Therefore avoid the sanity check, unless enforced by kernel
936 * configuration or command line option.
937 *
938 * When dynamic FPU features are supported, the check is also enforced when
939 * the task has permissions to use dynamic features. Tasks which have no
940 * permission are checked against the size of the non-dynamic feature set
941 * if strict checking is enabled. This avoids forcing all tasks on the
942 * system to allocate large sigaltstacks even if they are never going
943 * to use a dynamic feature. As this is serialized via sighand::siglock
944 * any permission request for a dynamic feature either happened already
945 * or will see the newly install sigaltstack size in the permission checks.
946 */
sigaltstack_size_valid(size_t ss_size)947 bool sigaltstack_size_valid(size_t ss_size)
948 {
949 unsigned long fsize = max_frame_size - fpu_default_state_size;
950 u64 mask;
951
952 lockdep_assert_held(¤t->sighand->siglock);
953
954 if (!fpu_state_size_dynamic() && !strict_sigaltstack_size)
955 return true;
956
957 fsize += current->group_leader->thread.fpu.perm.__user_state_size;
958 if (likely(ss_size > fsize))
959 return true;
960
961 if (strict_sigaltstack_size)
962 return ss_size > fsize;
963
964 mask = current->group_leader->thread.fpu.perm.__state_perm;
965 if (mask & XFEATURE_MASK_USER_DYNAMIC)
966 return ss_size > fsize;
967
968 return true;
969 }
970 #endif /* CONFIG_DYNAMIC_SIGFRAME */
971
972 #ifdef CONFIG_X86_X32_ABI
COMPAT_SYSCALL_DEFINE0(x32_rt_sigreturn)973 COMPAT_SYSCALL_DEFINE0(x32_rt_sigreturn)
974 {
975 struct pt_regs *regs = current_pt_regs();
976 struct rt_sigframe_x32 __user *frame;
977 sigset_t set;
978 unsigned long uc_flags;
979
980 frame = (struct rt_sigframe_x32 __user *)(regs->sp - 8);
981
982 if (!access_ok(frame, sizeof(*frame)))
983 goto badframe;
984 if (__get_user(set.sig[0], (__u64 __user *)&frame->uc.uc_sigmask))
985 goto badframe;
986 if (__get_user(uc_flags, &frame->uc.uc_flags))
987 goto badframe;
988
989 set_current_blocked(&set);
990
991 if (!restore_sigcontext(regs, &frame->uc.uc_mcontext, uc_flags))
992 goto badframe;
993
994 if (compat_restore_altstack(&frame->uc.uc_stack))
995 goto badframe;
996
997 return regs->ax;
998
999 badframe:
1000 signal_fault(regs, frame, "x32 rt_sigreturn");
1001 return 0;
1002 }
1003 #endif
1004