409 lines
11 KiB
C
409 lines
11 KiB
C
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// SPDX-License-Identifier: GPL-2.0
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/*
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* Copyright (C) 1991, 1992 Linus Torvalds
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* Copyright (C) 2000, 2001, 2002 Andi Kleen SuSE Labs
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*
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* 1997-11-28 Modified for POSIX.1b signals by Richard Henderson
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* 2000-06-20 Pentium III FXSR, SSE support by Gareth Hughes
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* 2000-2002 x86-64 support by Andi Kleen
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*/
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include <linux/sched.h>
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#include <linux/sched/task_stack.h>
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#include <linux/mm.h>
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#include <linux/smp.h>
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#include <linux/kernel.h>
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#include <linux/kstrtox.h>
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#include <linux/errno.h>
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#include <linux/wait.h>
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#include <linux/unistd.h>
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#include <linux/stddef.h>
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#include <linux/personality.h>
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#include <linux/uaccess.h>
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#include <linux/user-return-notifier.h>
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#include <linux/uprobes.h>
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#include <linux/context_tracking.h>
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#include <linux/entry-common.h>
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#include <linux/syscalls.h>
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#include <asm/processor.h>
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#include <asm/ucontext.h>
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#include <asm/fpu/signal.h>
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#include <asm/fpu/xstate.h>
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#include <asm/vdso.h>
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#include <asm/mce.h>
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#include <asm/sighandling.h>
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#include <asm/vm86.h>
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#include <asm/syscall.h>
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#include <asm/sigframe.h>
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#include <asm/signal.h>
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static inline int is_ia32_compat_frame(struct ksignal *ksig)
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{
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return IS_ENABLED(CONFIG_IA32_EMULATION) &&
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ksig->ka.sa.sa_flags & SA_IA32_ABI;
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}
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static inline int is_ia32_frame(struct ksignal *ksig)
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{
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return IS_ENABLED(CONFIG_X86_32) || is_ia32_compat_frame(ksig);
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}
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static inline int is_x32_frame(struct ksignal *ksig)
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{
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return IS_ENABLED(CONFIG_X86_X32_ABI) &&
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ksig->ka.sa.sa_flags & SA_X32_ABI;
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}
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/*
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* Set up a signal frame.
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*/
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/* x86 ABI requires 16-byte alignment */
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#define FRAME_ALIGNMENT 16UL
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#define MAX_FRAME_PADDING (FRAME_ALIGNMENT - 1)
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/*
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* Determine which stack to use..
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*/
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void __user *
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get_sigframe(struct ksignal *ksig, struct pt_regs *regs, size_t frame_size,
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void __user **fpstate)
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{
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struct k_sigaction *ka = &ksig->ka;
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int ia32_frame = is_ia32_frame(ksig);
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/* Default to using normal stack */
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bool nested_altstack = on_sig_stack(regs->sp);
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bool entering_altstack = false;
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unsigned long math_size = 0;
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unsigned long sp = regs->sp;
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unsigned long buf_fx = 0;
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/* redzone */
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if (!ia32_frame)
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sp -= 128;
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/* This is the X/Open sanctioned signal stack switching. */
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if (ka->sa.sa_flags & SA_ONSTACK) {
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/*
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* This checks nested_altstack via sas_ss_flags(). Sensible
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* programs use SS_AUTODISARM, which disables that check, and
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* programs that don't use SS_AUTODISARM get compatible.
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*/
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if (sas_ss_flags(sp) == 0) {
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sp = current->sas_ss_sp + current->sas_ss_size;
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entering_altstack = true;
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}
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} else if (ia32_frame &&
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!nested_altstack &&
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regs->ss != __USER_DS &&
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!(ka->sa.sa_flags & SA_RESTORER) &&
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ka->sa.sa_restorer) {
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/* This is the legacy signal stack switching. */
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sp = (unsigned long) ka->sa.sa_restorer;
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entering_altstack = true;
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}
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sp = fpu__alloc_mathframe(sp, ia32_frame, &buf_fx, &math_size);
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*fpstate = (void __user *)sp;
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sp -= frame_size;
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if (ia32_frame)
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/*
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* Align the stack pointer according to the i386 ABI,
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* i.e. so that on function entry ((sp + 4) & 15) == 0.
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*/
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sp = ((sp + 4) & -FRAME_ALIGNMENT) - 4;
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else
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sp = round_down(sp, FRAME_ALIGNMENT) - 8;
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/*
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* If we are on the alternate signal stack and would overflow it, don't.
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* Return an always-bogus address instead so we will die with SIGSEGV.
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*/
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if (unlikely((nested_altstack || entering_altstack) &&
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!__on_sig_stack(sp))) {
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if (show_unhandled_signals && printk_ratelimit())
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pr_info("%s[%d] overflowed sigaltstack\n",
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current->comm, task_pid_nr(current));
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return (void __user *)-1L;
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}
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/* save i387 and extended state */
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if (!copy_fpstate_to_sigframe(*fpstate, (void __user *)buf_fx, math_size))
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return (void __user *)-1L;
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return (void __user *)sp;
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}
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/*
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* There are four different struct types for signal frame: sigframe_ia32,
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* rt_sigframe_ia32, rt_sigframe_x32, and rt_sigframe. Use the worst case
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* -- the largest size. It means the size for 64-bit apps is a bit more
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* than needed, but this keeps the code simple.
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*/
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#if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION)
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# define MAX_FRAME_SIGINFO_UCTXT_SIZE sizeof(struct sigframe_ia32)
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#else
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# define MAX_FRAME_SIGINFO_UCTXT_SIZE sizeof(struct rt_sigframe)
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#endif
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/*
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* The FP state frame contains an XSAVE buffer which must be 64-byte aligned.
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* If a signal frame starts at an unaligned address, extra space is required.
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* This is the max alignment padding, conservatively.
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*/
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#define MAX_XSAVE_PADDING 63UL
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/*
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* The frame data is composed of the following areas and laid out as:
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*
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* -------------------------
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* | alignment padding |
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* -------------------------
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* | (f)xsave frame |
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* -------------------------
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* | fsave header |
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* -------------------------
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* | alignment padding |
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* -------------------------
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* | siginfo + ucontext |
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* -------------------------
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*/
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/* max_frame_size tells userspace the worst case signal stack size. */
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static unsigned long __ro_after_init max_frame_size;
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static unsigned int __ro_after_init fpu_default_state_size;
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void __init init_sigframe_size(void)
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{
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fpu_default_state_size = fpu__get_fpstate_size();
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max_frame_size = MAX_FRAME_SIGINFO_UCTXT_SIZE + MAX_FRAME_PADDING;
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max_frame_size += fpu_default_state_size + MAX_XSAVE_PADDING;
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/* Userspace expects an aligned size. */
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max_frame_size = round_up(max_frame_size, FRAME_ALIGNMENT);
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pr_info("max sigframe size: %lu\n", max_frame_size);
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}
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unsigned long get_sigframe_size(void)
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{
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return max_frame_size;
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}
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static int
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setup_rt_frame(struct ksignal *ksig, struct pt_regs *regs)
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{
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/* Perform fixup for the pre-signal frame. */
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rseq_signal_deliver(ksig, regs);
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/* Set up the stack frame */
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if (is_ia32_frame(ksig)) {
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if (ksig->ka.sa.sa_flags & SA_SIGINFO)
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return ia32_setup_rt_frame(ksig, regs);
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else
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return ia32_setup_frame(ksig, regs);
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} else if (is_x32_frame(ksig)) {
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return x32_setup_rt_frame(ksig, regs);
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} else {
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return x64_setup_rt_frame(ksig, regs);
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}
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}
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static void
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handle_signal(struct ksignal *ksig, struct pt_regs *regs)
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{
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bool stepping, failed;
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struct fpu *fpu = ¤t->thread.fpu;
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if (v8086_mode(regs))
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save_v86_state((struct kernel_vm86_regs *) regs, VM86_SIGNAL);
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/* Are we from a system call? */
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if (syscall_get_nr(current, regs) != -1) {
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/* If so, check system call restarting.. */
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switch (syscall_get_error(current, regs)) {
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case -ERESTART_RESTARTBLOCK:
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case -ERESTARTNOHAND:
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regs->ax = -EINTR;
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break;
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case -ERESTARTSYS:
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if (!(ksig->ka.sa.sa_flags & SA_RESTART)) {
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regs->ax = -EINTR;
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break;
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}
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fallthrough;
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case -ERESTARTNOINTR:
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regs->ax = regs->orig_ax;
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regs->ip -= 2;
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break;
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}
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}
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/*
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* If TF is set due to a debugger (TIF_FORCED_TF), clear TF now
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* so that register information in the sigcontext is correct and
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* then notify the tracer before entering the signal handler.
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*/
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stepping = test_thread_flag(TIF_SINGLESTEP);
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if (stepping)
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user_disable_single_step(current);
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failed = (setup_rt_frame(ksig, regs) < 0);
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if (!failed) {
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/*
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* Clear the direction flag as per the ABI for function entry.
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*
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* Clear RF when entering the signal handler, because
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* it might disable possible debug exception from the
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* signal handler.
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*
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* Clear TF for the case when it wasn't set by debugger to
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* avoid the recursive send_sigtrap() in SIGTRAP handler.
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*/
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regs->flags &= ~(X86_EFLAGS_DF|X86_EFLAGS_RF|X86_EFLAGS_TF);
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/*
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* Ensure the signal handler starts with the new fpu state.
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*/
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fpu__clear_user_states(fpu);
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}
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signal_setup_done(failed, ksig, stepping);
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}
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static inline unsigned long get_nr_restart_syscall(const struct pt_regs *regs)
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{
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#ifdef CONFIG_IA32_EMULATION
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if (current->restart_block.arch_data & TS_COMPAT)
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return __NR_ia32_restart_syscall;
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#endif
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#ifdef CONFIG_X86_X32_ABI
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return __NR_restart_syscall | (regs->orig_ax & __X32_SYSCALL_BIT);
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#else
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return __NR_restart_syscall;
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#endif
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}
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/*
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* Note that 'init' is a special process: it doesn't get signals it doesn't
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* want to handle. Thus you cannot kill init even with a SIGKILL even by
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* mistake.
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*/
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void arch_do_signal_or_restart(struct pt_regs *regs)
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{
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struct ksignal ksig;
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if (get_signal(&ksig)) {
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/* Whee! Actually deliver the signal. */
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handle_signal(&ksig, regs);
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return;
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}
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/* Did we come from a system call? */
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if (syscall_get_nr(current, regs) != -1) {
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/* Restart the system call - no handlers present */
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switch (syscall_get_error(current, regs)) {
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case -ERESTARTNOHAND:
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case -ERESTARTSYS:
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case -ERESTARTNOINTR:
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regs->ax = regs->orig_ax;
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regs->ip -= 2;
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break;
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case -ERESTART_RESTARTBLOCK:
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regs->ax = get_nr_restart_syscall(regs);
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regs->ip -= 2;
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break;
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}
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}
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/*
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* If there's no signal to deliver, we just put the saved sigmask
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* back.
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*/
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restore_saved_sigmask();
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}
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void signal_fault(struct pt_regs *regs, void __user *frame, char *where)
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{
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struct task_struct *me = current;
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if (show_unhandled_signals && printk_ratelimit()) {
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printk("%s"
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"%s[%d] bad frame in %s frame:%p ip:%lx sp:%lx orax:%lx",
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task_pid_nr(current) > 1 ? KERN_INFO : KERN_EMERG,
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me->comm, me->pid, where, frame,
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regs->ip, regs->sp, regs->orig_ax);
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print_vma_addr(KERN_CONT " in ", regs->ip);
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pr_cont("\n");
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}
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force_sig(SIGSEGV);
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}
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#ifdef CONFIG_DYNAMIC_SIGFRAME
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#ifdef CONFIG_STRICT_SIGALTSTACK_SIZE
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static bool strict_sigaltstack_size __ro_after_init = true;
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#else
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static bool strict_sigaltstack_size __ro_after_init = false;
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#endif
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static int __init strict_sas_size(char *arg)
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{
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return kstrtobool(arg, &strict_sigaltstack_size) == 0;
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}
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__setup("strict_sas_size", strict_sas_size);
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/*
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* MINSIGSTKSZ is 2048 and can't be changed despite the fact that AVX512
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* exceeds that size already. As such programs might never use the
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* sigaltstack they just continued to work. While always checking against
|
||
|
|
* the real size would be correct, this might be considered a regression.
|
||
|
|
*
|
||
|
|
* Therefore avoid the sanity check, unless enforced by kernel
|
||
|
|
* configuration or command line option.
|
||
|
|
*
|
||
|
|
* When dynamic FPU features are supported, the check is also enforced when
|
||
|
|
* the task has permissions to use dynamic features. Tasks which have no
|
||
|
|
* permission are checked against the size of the non-dynamic feature set
|
||
|
|
* if strict checking is enabled. This avoids forcing all tasks on the
|
||
|
|
* system to allocate large sigaltstacks even if they are never going
|
||
|
|
* to use a dynamic feature. As this is serialized via sighand::siglock
|
||
|
|
* any permission request for a dynamic feature either happened already
|
||
|
|
* or will see the newly install sigaltstack size in the permission checks.
|
||
|
|
*/
|
||
|
|
bool sigaltstack_size_valid(size_t ss_size)
|
||
|
|
{
|
||
|
|
unsigned long fsize = max_frame_size - fpu_default_state_size;
|
||
|
|
u64 mask;
|
||
|
|
|
||
|
|
lockdep_assert_held(¤t->sighand->siglock);
|
||
|
|
|
||
|
|
if (!fpu_state_size_dynamic() && !strict_sigaltstack_size)
|
||
|
|
return true;
|
||
|
|
|
||
|
|
fsize += current->group_leader->thread.fpu.perm.__user_state_size;
|
||
|
|
if (likely(ss_size > fsize))
|
||
|
|
return true;
|
||
|
|
|
||
|
|
if (strict_sigaltstack_size)
|
||
|
|
return ss_size > fsize;
|
||
|
|
|
||
|
|
mask = current->group_leader->thread.fpu.perm.__state_perm;
|
||
|
|
if (mask & XFEATURE_MASK_USER_DYNAMIC)
|
||
|
|
return ss_size > fsize;
|
||
|
|
|
||
|
|
return true;
|
||
|
|
}
|
||
|
|
#endif /* CONFIG_DYNAMIC_SIGFRAME */
|