cced0b24bb
There are several copies of get_eflags() and set_eflags() and they all are buggy. Consolidate them and fix them. The fixes are: Add memory clobbers. These are probably unnecessary but they make sure that the compiler doesn't move something past one of these calls when it shouldn't. Respect the redzone on x86_64. There has no failure been observed related to this, but it's definitely a bug. Signed-off-by: Andy Lutomirski <luto@kernel.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lkml.kernel.org/r/982ce58ae8dea2f1e57093ee894760e35267e751.1593191971.git.luto@kernel.org
86 lines
2.0 KiB
C
86 lines
2.0 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* syscall_nt.c - checks syscalls with NT set
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* Copyright (c) 2014-2015 Andrew Lutomirski
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*
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* Some obscure user-space code requires the ability to make system calls
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* with FLAGS.NT set. Make sure it works.
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*/
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#include <stdio.h>
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#include <unistd.h>
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#include <string.h>
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#include <signal.h>
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#include <err.h>
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#include <sys/syscall.h>
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#include "helpers.h"
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static unsigned int nerrs;
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static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *),
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int flags)
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{
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struct sigaction sa;
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memset(&sa, 0, sizeof(sa));
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sa.sa_sigaction = handler;
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sa.sa_flags = SA_SIGINFO | flags;
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sigemptyset(&sa.sa_mask);
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if (sigaction(sig, &sa, 0))
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err(1, "sigaction");
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}
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static void sigtrap(int sig, siginfo_t *si, void *ctx_void)
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{
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}
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static void do_it(unsigned long extraflags)
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{
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unsigned long flags;
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set_eflags(get_eflags() | extraflags);
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syscall(SYS_getpid);
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flags = get_eflags();
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set_eflags(X86_EFLAGS_IF | X86_EFLAGS_FIXED);
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if ((flags & extraflags) == extraflags) {
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printf("[OK]\tThe syscall worked and flags are still set\n");
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} else {
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printf("[FAIL]\tThe syscall worked but flags were cleared (flags = 0x%lx but expected 0x%lx set)\n",
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flags, extraflags);
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nerrs++;
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}
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}
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int main(void)
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{
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printf("[RUN]\tSet NT and issue a syscall\n");
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do_it(X86_EFLAGS_NT);
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printf("[RUN]\tSet AC and issue a syscall\n");
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do_it(X86_EFLAGS_AC);
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printf("[RUN]\tSet NT|AC and issue a syscall\n");
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do_it(X86_EFLAGS_NT | X86_EFLAGS_AC);
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/*
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* Now try it again with TF set -- TF forces returns via IRET in all
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* cases except non-ptregs-using 64-bit full fast path syscalls.
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*/
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sethandler(SIGTRAP, sigtrap, 0);
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printf("[RUN]\tSet TF and issue a syscall\n");
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do_it(X86_EFLAGS_TF);
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printf("[RUN]\tSet NT|TF and issue a syscall\n");
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do_it(X86_EFLAGS_NT | X86_EFLAGS_TF);
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printf("[RUN]\tSet AC|TF and issue a syscall\n");
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do_it(X86_EFLAGS_AC | X86_EFLAGS_TF);
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printf("[RUN]\tSet NT|AC|TF and issue a syscall\n");
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do_it(X86_EFLAGS_NT | X86_EFLAGS_AC | X86_EFLAGS_TF);
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return nerrs == 0 ? 0 : 1;
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}
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