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