1deb9c5dfb
The kernel was allowing any component of the pt_regs to be updated either by signal handlers writing to the stack, or by processes writing via PTRACE_POKEUSR or PTRACE_SETREGS, which meant they could set their PL up from 0 to 1 and get access to kernel code and data (or, in practice, cause a kernel panic). We now always reset the ex1 field, allowing the user to set their ICS bit only. Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>
368 lines
9.8 KiB
C
368 lines
9.8 KiB
C
/*
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* Copyright (C) 1991, 1992 Linus Torvalds
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* Copyright 2010 Tilera Corporation. All Rights Reserved.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation, version 2.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
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* NON INFRINGEMENT. See the GNU General Public License for
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* more details.
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*/
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#include <linux/sched.h>
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#include <linux/mm.h>
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#include <linux/smp.h>
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#include <linux/smp_lock.h>
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#include <linux/kernel.h>
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#include <linux/signal.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/suspend.h>
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#include <linux/ptrace.h>
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#include <linux/elf.h>
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#include <linux/compat.h>
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#include <linux/syscalls.h>
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#include <linux/uaccess.h>
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#include <asm/processor.h>
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#include <asm/ucontext.h>
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#include <asm/sigframe.h>
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#include <asm/syscalls.h>
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#include <arch/interrupts.h>
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#define DEBUG_SIG 0
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#define _BLOCKABLE (~(sigmask(SIGKILL) | sigmask(SIGSTOP)))
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SYSCALL_DEFINE3(sigaltstack, const stack_t __user *, uss,
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stack_t __user *, uoss, struct pt_regs *, regs)
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{
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return do_sigaltstack(uss, uoss, regs->sp);
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}
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/*
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* Do a signal return; undo the signal stack.
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*/
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int restore_sigcontext(struct pt_regs *regs,
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struct sigcontext __user *sc, long *pr0)
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{
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int err = 0;
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int i;
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/* Always make any pending restarted system calls return -EINTR */
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current_thread_info()->restart_block.fn = do_no_restart_syscall;
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/*
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* Enforce that sigcontext is like pt_regs, and doesn't mess
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* up our stack alignment rules.
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*/
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BUILD_BUG_ON(sizeof(struct sigcontext) != sizeof(struct pt_regs));
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BUILD_BUG_ON(sizeof(struct sigcontext) % 8 != 0);
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for (i = 0; i < sizeof(struct pt_regs)/sizeof(long); ++i)
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err |= __get_user(regs->regs[i], &sc->gregs[i]);
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/* Ensure that the PL is always set to USER_PL. */
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regs->ex1 = PL_ICS_EX1(USER_PL, EX1_ICS(regs->ex1));
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regs->faultnum = INT_SWINT_1_SIGRETURN;
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err |= __get_user(*pr0, &sc->gregs[0]);
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return err;
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}
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/* sigreturn() returns long since it restores r0 in the interrupted code. */
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SYSCALL_DEFINE1(rt_sigreturn, struct pt_regs *, regs)
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{
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struct rt_sigframe __user *frame =
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(struct rt_sigframe __user *)(regs->sp);
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sigset_t set;
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long r0;
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if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
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goto badframe;
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if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
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goto badframe;
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sigdelsetmask(&set, ~_BLOCKABLE);
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spin_lock_irq(¤t->sighand->siglock);
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current->blocked = set;
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recalc_sigpending();
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spin_unlock_irq(¤t->sighand->siglock);
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if (restore_sigcontext(regs, &frame->uc.uc_mcontext, &r0))
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goto badframe;
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if (do_sigaltstack(&frame->uc.uc_stack, NULL, regs->sp) == -EFAULT)
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goto badframe;
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return r0;
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badframe:
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force_sig(SIGSEGV, current);
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return 0;
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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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int setup_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs)
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{
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int i, err = 0;
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for (i = 0; i < sizeof(struct pt_regs)/sizeof(long); ++i)
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err |= __put_user(regs->regs[i], &sc->gregs[i]);
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return err;
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}
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/*
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* Determine which stack to use..
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*/
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static inline void __user *get_sigframe(struct k_sigaction *ka,
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struct pt_regs *regs,
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size_t frame_size)
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{
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unsigned long sp;
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/* Default to using normal stack */
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sp = regs->sp;
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/*
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* If we are on the alternate signal stack and would overflow
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* it, don't. Return an always-bogus address instead so we
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* will die with SIGSEGV.
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*/
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if (on_sig_stack(sp) && !likely(on_sig_stack(sp - frame_size)))
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return (void __user __force *)-1UL;
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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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if (sas_ss_flags(sp) == 0)
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sp = current->sas_ss_sp + current->sas_ss_size;
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}
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sp -= frame_size;
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/*
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* Align the stack pointer according to the TILE ABI,
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* i.e. so that on function entry (sp & 15) == 0.
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*/
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sp &= -16UL;
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return (void __user *) sp;
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}
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static int setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
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sigset_t *set, struct pt_regs *regs)
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{
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unsigned long restorer;
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struct rt_sigframe __user *frame;
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int err = 0;
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int usig;
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frame = get_sigframe(ka, regs, sizeof(*frame));
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if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
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goto give_sigsegv;
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usig = current_thread_info()->exec_domain
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&& current_thread_info()->exec_domain->signal_invmap
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&& sig < 32
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? current_thread_info()->exec_domain->signal_invmap[sig]
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: sig;
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/* Always write at least the signal number for the stack backtracer. */
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if (ka->sa.sa_flags & SA_SIGINFO) {
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/* At sigreturn time, restore the callee-save registers too. */
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err |= copy_siginfo_to_user(&frame->info, info);
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regs->flags |= PT_FLAGS_RESTORE_REGS;
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} else {
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err |= __put_user(info->si_signo, &frame->info.si_signo);
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}
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/* Create the ucontext. */
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err |= __clear_user(&frame->save_area, sizeof(frame->save_area));
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err |= __put_user(0, &frame->uc.uc_flags);
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err |= __put_user(NULL, &frame->uc.uc_link);
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err |= __put_user((void __user *)(current->sas_ss_sp),
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&frame->uc.uc_stack.ss_sp);
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err |= __put_user(sas_ss_flags(regs->sp),
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&frame->uc.uc_stack.ss_flags);
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err |= __put_user(current->sas_ss_size, &frame->uc.uc_stack.ss_size);
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err |= setup_sigcontext(&frame->uc.uc_mcontext, regs);
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err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
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if (err)
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goto give_sigsegv;
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restorer = VDSO_BASE;
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if (ka->sa.sa_flags & SA_RESTORER)
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restorer = (unsigned long) ka->sa.sa_restorer;
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/*
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* Set up registers for signal handler.
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* Registers that we don't modify keep the value they had from
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* user-space at the time we took the signal.
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* We always pass siginfo and mcontext, regardless of SA_SIGINFO,
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* since some things rely on this (e.g. glibc's debug/segfault.c).
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*/
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regs->pc = (unsigned long) ka->sa.sa_handler;
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regs->ex1 = PL_ICS_EX1(USER_PL, 1); /* set crit sec in handler */
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regs->sp = (unsigned long) frame;
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regs->lr = restorer;
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regs->regs[0] = (unsigned long) usig;
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regs->regs[1] = (unsigned long) &frame->info;
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regs->regs[2] = (unsigned long) &frame->uc;
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regs->flags |= PT_FLAGS_CALLER_SAVES;
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/*
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* Notify any tracer that was single-stepping it.
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* The tracer may want to single-step inside the
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* handler too.
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*/
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if (test_thread_flag(TIF_SINGLESTEP))
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ptrace_notify(SIGTRAP);
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return 0;
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give_sigsegv:
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force_sigsegv(sig, current);
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return -EFAULT;
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}
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/*
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* OK, we're invoking a handler
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*/
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static int handle_signal(unsigned long sig, siginfo_t *info,
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struct k_sigaction *ka, sigset_t *oldset,
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struct pt_regs *regs)
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{
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int ret;
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/* Are we from a system call? */
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if (regs->faultnum == INT_SWINT_1) {
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/* If so, check system call restarting.. */
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switch (regs->regs[0]) {
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case -ERESTART_RESTARTBLOCK:
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case -ERESTARTNOHAND:
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regs->regs[0] = -EINTR;
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break;
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case -ERESTARTSYS:
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if (!(ka->sa.sa_flags & SA_RESTART)) {
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regs->regs[0] = -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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/* Reload caller-saves to restore r0..r5 and r10. */
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regs->flags |= PT_FLAGS_CALLER_SAVES;
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regs->regs[0] = regs->orig_r0;
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regs->pc -= 8;
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}
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}
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/* Set up the stack frame */
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#ifdef CONFIG_COMPAT
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if (is_compat_task())
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ret = compat_setup_rt_frame(sig, ka, info, oldset, regs);
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else
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#endif
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ret = setup_rt_frame(sig, ka, info, oldset, regs);
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if (ret == 0) {
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/* This code is only called from system calls or from
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* the work_pending path in the return-to-user code, and
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* either way we can re-enable interrupts unconditionally.
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*/
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spin_lock_irq(¤t->sighand->siglock);
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sigorsets(¤t->blocked,
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¤t->blocked, &ka->sa.sa_mask);
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if (!(ka->sa.sa_flags & SA_NODEFER))
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sigaddset(¤t->blocked, sig);
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recalc_sigpending();
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spin_unlock_irq(¤t->sighand->siglock);
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}
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return ret;
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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 do_signal(struct pt_regs *regs)
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{
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siginfo_t info;
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int signr;
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struct k_sigaction ka;
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sigset_t *oldset;
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/*
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* i386 will check if we're coming from kernel mode and bail out
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* here. In my experience this just turns weird crashes into
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* weird spin-hangs. But if we find a case where this seems
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* helpful, we can reinstate the check on "!user_mode(regs)".
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*/
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if (current_thread_info()->status & TS_RESTORE_SIGMASK)
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oldset = ¤t->saved_sigmask;
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else
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oldset = ¤t->blocked;
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signr = get_signal_to_deliver(&info, &ka, regs, NULL);
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if (signr > 0) {
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/* Whee! Actually deliver the signal. */
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if (handle_signal(signr, &info, &ka, oldset, regs) == 0) {
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/*
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* A signal was successfully delivered; the saved
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* sigmask will have been stored in the signal frame,
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* and will be restored by sigreturn, so we can simply
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* clear the TS_RESTORE_SIGMASK flag.
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*/
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current_thread_info()->status &= ~TS_RESTORE_SIGMASK;
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}
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goto done;
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}
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/* Did we come from a system call? */
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if (regs->faultnum == INT_SWINT_1) {
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/* Restart the system call - no handlers present */
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switch (regs->regs[0]) {
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case -ERESTARTNOHAND:
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case -ERESTARTSYS:
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case -ERESTARTNOINTR:
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regs->flags |= PT_FLAGS_CALLER_SAVES;
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regs->regs[0] = regs->orig_r0;
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regs->pc -= 8;
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break;
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case -ERESTART_RESTARTBLOCK:
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regs->flags |= PT_FLAGS_CALLER_SAVES;
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regs->regs[TREG_SYSCALL_NR] = __NR_restart_syscall;
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regs->pc -= 8;
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break;
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}
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}
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/* If there's no signal to deliver, just put the saved sigmask back. */
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if (current_thread_info()->status & TS_RESTORE_SIGMASK) {
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current_thread_info()->status &= ~TS_RESTORE_SIGMASK;
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sigprocmask(SIG_SETMASK, ¤t->saved_sigmask, NULL);
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}
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done:
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/* Avoid double syscall restart if there are nested signals. */
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regs->faultnum = INT_SWINT_1_SIGRETURN;
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}
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