287 lines
7.7 KiB
C
287 lines
7.7 KiB
C
|
/* SPDX-License-Identifier: GPL-2.0 */
|
||
|
|
/*
|
||
|
|
* mov_ss_trap.c: Exercise the bizarre side effects of a watchpoint on MOV SS
|
||
|
|
*
|
||
|
|
* This does MOV SS from a watchpointed address followed by various
|
||
|
|
* types of kernel entries. A MOV SS that hits a watchpoint will queue
|
||
|
|
* up a #DB trap but will not actually deliver that trap. The trap
|
||
|
|
* will be delivered after the next instruction instead. The CPU's logic
|
||
|
|
* seems to be:
|
||
|
|
*
|
||
|
|
* - Any fault: drop the pending #DB trap.
|
||
|
|
* - INT $N, INT3, INTO, SYSCALL, SYSENTER: enter the kernel and then
|
||
|
|
* deliver #DB.
|
||
|
|
* - ICEBP: enter the kernel but do not deliver the watchpoint trap
|
||
|
|
* - breakpoint: only one #DB is delivered (phew!)
|
||
|
|
*
|
||
|
|
* There are plenty of ways for a kernel to handle this incorrectly. This
|
||
|
|
* test tries to exercise all the cases.
|
||
|
|
*
|
||
|
|
* This should mostly cover CVE-2018-1087 and CVE-2018-8897.
|
||
|
|
*/
|
||
|
|
#define _GNU_SOURCE
|
||
|
|
|
||
|
|
#include <stdlib.h>
|
||
|
|
#include <sys/ptrace.h>
|
||
|
|
#include <sys/types.h>
|
||
|
|
#include <sys/wait.h>
|
||
|
|
#include <sys/user.h>
|
||
|
|
#include <sys/syscall.h>
|
||
|
|
#include <unistd.h>
|
||
|
|
#include <errno.h>
|
||
|
|
#include <stddef.h>
|
||
|
|
#include <stdio.h>
|
||
|
|
#include <err.h>
|
||
|
|
#include <string.h>
|
||
|
|
#include <setjmp.h>
|
||
|
|
#include <sys/prctl.h>
|
||
|
|
|
||
|
|
#define X86_EFLAGS_RF (1UL << 16)
|
||
|
|
|
||
|
|
#if __x86_64__
|
||
|
|
# define REG_IP REG_RIP
|
||
|
|
#else
|
||
|
|
# define REG_IP REG_EIP
|
||
|
|
#endif
|
||
|
|
|
||
|
|
unsigned short ss;
|
||
|
|
extern unsigned char breakpoint_insn[];
|
||
|
|
sigjmp_buf jmpbuf;
|
||
|
|
static unsigned char altstack_data[SIGSTKSZ];
|
||
|
|
|
||
|
|
static void enable_watchpoint(void)
|
||
|
|
{
|
||
|
|
pid_t parent = getpid();
|
||
|
|
int status;
|
||
|
|
|
||
|
|
pid_t child = fork();
|
||
|
|
if (child < 0)
|
||
|
|
err(1, "fork");
|
||
|
|
|
||
|
|
if (child) {
|
||
|
|
if (waitpid(child, &status, 0) != child)
|
||
|
|
err(1, "waitpid for child");
|
||
|
|
} else {
|
||
|
|
unsigned long dr0, dr1, dr7;
|
||
|
|
|
||
|
|
dr0 = (unsigned long)&ss;
|
||
|
|
dr1 = (unsigned long)breakpoint_insn;
|
||
|
|
dr7 = ((1UL << 1) | /* G0 */
|
||
|
|
(3UL << 16) | /* RW0 = read or write */
|
||
|
|
(1UL << 18) | /* LEN0 = 2 bytes */
|
||
|
|
(1UL << 3)); /* G1, RW1 = insn */
|
||
|
|
|
||
|
|
if (ptrace(PTRACE_ATTACH, parent, NULL, NULL) != 0)
|
||
|
|
err(1, "PTRACE_ATTACH");
|
||
|
|
|
||
|
|
if (waitpid(parent, &status, 0) != parent)
|
||
|
|
err(1, "waitpid for child");
|
||
|
|
|
||
|
|
if (ptrace(PTRACE_POKEUSER, parent, (void *)offsetof(struct user, u_debugreg[0]), dr0) != 0)
|
||
|
|
err(1, "PTRACE_POKEUSER DR0");
|
||
|
|
|
||
|
|
if (ptrace(PTRACE_POKEUSER, parent, (void *)offsetof(struct user, u_debugreg[1]), dr1) != 0)
|
||
|
|
err(1, "PTRACE_POKEUSER DR1");
|
||
|
|
|
||
|
|
if (ptrace(PTRACE_POKEUSER, parent, (void *)offsetof(struct user, u_debugreg[7]), dr7) != 0)
|
||
|
|
err(1, "PTRACE_POKEUSER DR7");
|
||
|
|
|
||
|
|
printf("\tDR0 = %lx, DR1 = %lx, DR7 = %lx\n", dr0, dr1, dr7);
|
||
|
|
|
||
|
|
if (ptrace(PTRACE_DETACH, parent, NULL, NULL) != 0)
|
||
|
|
err(1, "PTRACE_DETACH");
|
||
|
|
|
||
|
|
exit(0);
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *),
|
||
|
|
int flags)
|
||
|
|
{
|
||
|
|
struct sigaction sa;
|
||
|
|
memset(&sa, 0, sizeof(sa));
|
||
|
|
sa.sa_sigaction = handler;
|
||
|
|
sa.sa_flags = SA_SIGINFO | flags;
|
||
|
|
sigemptyset(&sa.sa_mask);
|
||
|
|
if (sigaction(sig, &sa, 0))
|
||
|
|
err(1, "sigaction");
|
||
|
|
}
|
||
|
|
|
||
|
|
static char const * const signames[] = {
|
||
|
|
[SIGSEGV] = "SIGSEGV",
|
||
|
|
[SIGBUS] = "SIBGUS",
|
||
|
|
[SIGTRAP] = "SIGTRAP",
|
||
|
|
[SIGILL] = "SIGILL",
|
||
|
|
};
|
||
|
|
|
||
|
|
static void sigtrap(int sig, siginfo_t *si, void *ctx_void)
|
||
|
|
{
|
||
|
|
ucontext_t *ctx = ctx_void;
|
||
|
|
|
||
|
|
printf("\tGot SIGTRAP with RIP=%lx, EFLAGS.RF=%d\n",
|
||
|
|
(unsigned long)ctx->uc_mcontext.gregs[REG_IP],
|
||
|
|
!!(ctx->uc_mcontext.gregs[REG_EFL] & X86_EFLAGS_RF));
|
||
|
|
}
|
||
|
|
|
||
|
|
static void handle_and_return(int sig, siginfo_t *si, void *ctx_void)
|
||
|
|
{
|
||
|
|
ucontext_t *ctx = ctx_void;
|
||
|
|
|
||
|
|
printf("\tGot %s with RIP=%lx\n", signames[sig],
|
||
|
|
(unsigned long)ctx->uc_mcontext.gregs[REG_IP]);
|
||
|
|
}
|
||
|
|
|
||
|
|
static void handle_and_longjmp(int sig, siginfo_t *si, void *ctx_void)
|
||
|
|
{
|
||
|
|
ucontext_t *ctx = ctx_void;
|
||
|
|
|
||
|
|
printf("\tGot %s with RIP=%lx\n", signames[sig],
|
||
|
|
(unsigned long)ctx->uc_mcontext.gregs[REG_IP]);
|
||
|
|
|
||
|
|
siglongjmp(jmpbuf, 1);
|
||
|
|
}
|
||
|
|
|
||
|
|
int main()
|
||
|
|
{
|
||
|
|
unsigned long nr;
|
||
|
|
|
||
|
|
asm volatile ("mov %%ss, %[ss]" : [ss] "=m" (ss));
|
||
|
|
printf("\tSS = 0x%hx, &SS = 0x%p\n", ss, &ss);
|
||
|
|
|
||
|
|
if (prctl(PR_SET_PTRACER, PR_SET_PTRACER_ANY, 0, 0, 0) == 0)
|
||
|
|
printf("\tPR_SET_PTRACER_ANY succeeded\n");
|
||
|
|
|
||
|
|
printf("\tSet up a watchpoint\n");
|
||
|
|
sethandler(SIGTRAP, sigtrap, 0);
|
||
|
|
enable_watchpoint();
|
||
|
|
|
||
|
|
printf("[RUN]\tRead from watched memory (should get SIGTRAP)\n");
|
||
|
|
asm volatile ("mov %[ss], %[tmp]" : [tmp] "=r" (nr) : [ss] "m" (ss));
|
||
|
|
|
||
|
|
printf("[RUN]\tMOV SS; INT3\n");
|
||
|
|
asm volatile ("mov %[ss], %%ss; int3" :: [ss] "m" (ss));
|
||
|
|
|
||
|
|
printf("[RUN]\tMOV SS; INT 3\n");
|
||
|
|
asm volatile ("mov %[ss], %%ss; .byte 0xcd, 0x3" :: [ss] "m" (ss));
|
||
|
|
|
||
|
|
printf("[RUN]\tMOV SS; CS CS INT3\n");
|
||
|
|
asm volatile ("mov %[ss], %%ss; .byte 0x2e, 0x2e; int3" :: [ss] "m" (ss));
|
||
|
|
|
||
|
|
printf("[RUN]\tMOV SS; CSx14 INT3\n");
|
||
|
|
asm volatile ("mov %[ss], %%ss; .fill 14,1,0x2e; int3" :: [ss] "m" (ss));
|
||
|
|
|
||
|
|
printf("[RUN]\tMOV SS; INT 4\n");
|
||
|
|
sethandler(SIGSEGV, handle_and_return, SA_RESETHAND);
|
||
|
|
asm volatile ("mov %[ss], %%ss; int $4" :: [ss] "m" (ss));
|
||
|
|
|
||
|
|
#ifdef __i386__
|
||
|
|
printf("[RUN]\tMOV SS; INTO\n");
|
||
|
|
sethandler(SIGSEGV, handle_and_return, SA_RESETHAND);
|
||
|
|
nr = -1;
|
||
|
|
asm volatile ("add $1, %[tmp]; mov %[ss], %%ss; into"
|
||
|
|
: [tmp] "+r" (nr) : [ss] "m" (ss));
|
||
|
|
#endif
|
||
|
|
|
||
|
|
if (sigsetjmp(jmpbuf, 1) == 0) {
|
||
|
|
printf("[RUN]\tMOV SS; ICEBP\n");
|
||
|
|
|
||
|
|
/* Some emulators (e.g. QEMU TCG) don't emulate ICEBP. */
|
||
|
|
sethandler(SIGILL, handle_and_longjmp, SA_RESETHAND);
|
||
|
|
|
||
|
|
asm volatile ("mov %[ss], %%ss; .byte 0xf1" :: [ss] "m" (ss));
|
||
|
|
}
|
||
|
|
|
||
|
|
if (sigsetjmp(jmpbuf, 1) == 0) {
|
||
|
|
printf("[RUN]\tMOV SS; CLI\n");
|
||
|
|
sethandler(SIGSEGV, handle_and_longjmp, SA_RESETHAND);
|
||
|
|
asm volatile ("mov %[ss], %%ss; cli" :: [ss] "m" (ss));
|
||
|
|
}
|
||
|
|
|
||
|
|
if (sigsetjmp(jmpbuf, 1) == 0) {
|
||
|
|
printf("[RUN]\tMOV SS; #PF\n");
|
||
|
|
sethandler(SIGSEGV, handle_and_longjmp, SA_RESETHAND);
|
||
|
|
asm volatile ("mov %[ss], %%ss; mov (-1), %[tmp]"
|
||
|
|
: [tmp] "=r" (nr) : [ss] "m" (ss));
|
||
|
|
}
|
||
|
|
|
||
|
|
/*
|
||
|
|
* INT $1: if #DB has DPL=3 and there isn't special handling,
|
||
|
|
* then the kernel will die.
|
||
|
|
*/
|
||
|
|
if (sigsetjmp(jmpbuf, 1) == 0) {
|
||
|
|
printf("[RUN]\tMOV SS; INT 1\n");
|
||
|
|
sethandler(SIGSEGV, handle_and_longjmp, SA_RESETHAND);
|
||
|
|
asm volatile ("mov %[ss], %%ss; int $1" :: [ss] "m" (ss));
|
||
|
|
}
|
||
|
|
|
||
|
|
#ifdef __x86_64__
|
||
|
|
/*
|
||
|
|
* In principle, we should test 32-bit SYSCALL as well, but
|
||
|
|
* the calling convention is so unpredictable that it's
|
||
|
|
* not obviously worth the effort.
|
||
|
|
*/
|
||
|
|
if (sigsetjmp(jmpbuf, 1) == 0) {
|
||
|
|
printf("[RUN]\tMOV SS; SYSCALL\n");
|
||
|
|
sethandler(SIGILL, handle_and_longjmp, SA_RESETHAND);
|
||
|
|
nr = SYS_getpid;
|
||
|
|
/*
|
||
|
|
* Toggle the high bit of RSP to make it noncanonical to
|
||
|
|
* strengthen this test on non-SMAP systems.
|
||
|
|
*/
|
||
|
|
asm volatile ("btc $63, %%rsp\n\t"
|
||
|
|
"mov %[ss], %%ss; syscall\n\t"
|
||
|
|
"btc $63, %%rsp"
|
||
|
|
: "+a" (nr) : [ss] "m" (ss)
|
||
|
|
: "rcx"
|
||
|
|
#ifdef __x86_64__
|
||
|
|
, "r11"
|
||
|
|
#endif
|
||
|
|
);
|
||
|
|
}
|
||
|
|
#endif
|
||
|
|
|
||
|
|
printf("[RUN]\tMOV SS; breakpointed NOP\n");
|
||
|
|
asm volatile ("mov %[ss], %%ss; breakpoint_insn: nop" :: [ss] "m" (ss));
|
||
|
|
|
||
|
|
/*
|
||
|
|
* Invoking SYSENTER directly breaks all the rules. Just handle
|
||
|
|
* the SIGSEGV.
|
||
|
|
*/
|
||
|
|
if (sigsetjmp(jmpbuf, 1) == 0) {
|
||
|
|
printf("[RUN]\tMOV SS; SYSENTER\n");
|
||
|
|
stack_t stack = {
|
||
|
|
.ss_sp = altstack_data,
|
||
|
|
.ss_size = SIGSTKSZ,
|
||
|
|
};
|
||
|
|
if (sigaltstack(&stack, NULL) != 0)
|
||
|
|
err(1, "sigaltstack");
|
||
|
|
sethandler(SIGSEGV, handle_and_longjmp, SA_RESETHAND | SA_ONSTACK);
|
||
|
|
nr = SYS_getpid;
|
||
|
|
/* Clear EBP first to make sure we segfault cleanly. */
|
||
|
|
asm volatile ("xorl %%ebp, %%ebp; mov %[ss], %%ss; SYSENTER" : "+a" (nr)
|
||
|
|
: [ss] "m" (ss) : "flags", "rcx"
|
||
|
|
#ifdef __x86_64__
|
||
|
|
, "r11"
|
||
|
|
#endif
|
||
|
|
);
|
||
|
|
|
||
|
|
/* We're unreachable here. SYSENTER forgets RIP. */
|
||
|
|
}
|
||
|
|
|
||
|
|
if (sigsetjmp(jmpbuf, 1) == 0) {
|
||
|
|
printf("[RUN]\tMOV SS; INT $0x80\n");
|
||
|
|
sethandler(SIGSEGV, handle_and_longjmp, SA_RESETHAND);
|
||
|
|
nr = 20; /* compat getpid */
|
||
|
|
asm volatile ("mov %[ss], %%ss; int $0x80"
|
||
|
|
: "+a" (nr) : [ss] "m" (ss)
|
||
|
|
: "flags"
|
||
|
|
#ifdef __x86_64__
|
||
|
|
, "r8", "r9", "r10", "r11"
|
||
|
|
#endif
|
||
|
|
);
|
||
|
|
}
|
||
|
|
|
||
|
|
printf("[OK]\tI aten't dead\n");
|
||
|
|
return 0;
|
||
|
|
}
|