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linux-stable/arch/s390/kernel/traps.c
Eric W. Biederman 686bf79203 signal: Replace force_fatal_sig with force_exit_sig when in doubt 
commit fcb116bc43 upstream.

Recently to prevent issues with SECCOMP_RET_KILL and similar signals
being changed before they are delivered SA_IMMUTABLE was added.

Unfortunately this broke debuggers[1][2] which reasonably expect
to be able to trap synchronous SIGTRAP and SIGSEGV even when
the target process is not configured to handle those signals.

Add force_exit_sig and use it instead of force_fatal_sig where
historically the code has directly called do_exit.  This has the
implementation benefits of going through the signal exit path
(including generating core dumps) without the danger of allowing
userspace to ignore or change these signals.

This avoids userspace regressions as older kernels exited with do_exit
which debuggers also can not intercept.

In the future is should be possible to improve the quality of
implementation of the kernel by changing some of these force_exit_sig
calls to force_fatal_sig.  That can be done where it matters on
a case-by-case basis with careful analysis.

Reported-by: Kyle Huey <me@kylehuey.com>
Reported-by: kernel test robot <oliver.sang@intel.com>
[1] https://lkml.kernel.org/r/CAP045AoMY4xf8aC_4QU_-j7obuEPYgTcnQQP3Yxk=2X90jtpjw@mail.gmail.com
[2] https://lkml.kernel.org/r/20211117150258.GB5403@xsang-OptiPlex-9020
Fixes: 00b06da29c ("signal: Add SA_IMMUTABLE to ensure forced siganls do not get changed")
Fixes: a3616a3c02 ("signal/m68k: Use force_sigsegv(SIGSEGV) in fpsp040_die")
Fixes: 83a1f27ad7 ("signal/powerpc: On swapcontext failure force SIGSEGV")
Fixes: 9bc508cf07 ("signal/s390: Use force_sigsegv in default_trap_handler")
Fixes: 086ec444f8 ("signal/sparc32: In setup_rt_frame and setup_fram use force_fatal_sig")
Fixes: c317d306d5 ("signal/sparc32: Exit with a fatal signal when try_to_clear_window_buffer fails")
Fixes: 695dd0d634 ("signal/x86: In emulate_vsyscall force a signal instead of calling do_exit")
Fixes: 1fbd60df8a ("signal/vm86_32: Properly send SIGSEGV when the vm86 state cannot be saved.")
Fixes: 941edc5bf1 ("exit/syscall_user_dispatch: Send ordinary signals on failure")
Link: https://lkml.kernel.org/r/871r3dqfv8.fsf_-_@email.froward.int.ebiederm.org
Reviewed-by: Kees Cook <keescook@chromium.org>
Tested-by: Kees Cook <keescook@chromium.org>
Tested-by: Kyle Huey <khuey@kylehuey.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Thomas Backlund <tmb@iki.fi>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-11-25 09:49:07 +01:00

409 lines
11 KiB
C
Raw Blame History

// SPDX-License-Identifier: GPL-2.0
/*
* S390 version
* Copyright IBM Corp. 1999, 2000
* Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com),
* Denis Joseph Barrow (djbarrow@de.ibm.com,barrow_dj@yahoo.com),
*
* Derived from "arch/i386/kernel/traps.c"
* Copyright (C) 1991, 1992 Linus Torvalds
*/
/*
* 'Traps.c' handles hardware traps and faults after we have saved some
* state in 'asm.s'.
*/
#include "asm/irqflags.h"
#include "asm/ptrace.h"
#include <linux/kprobes.h>
#include <linux/kdebug.h>
#include <linux/randomize_kstack.h>
#include <linux/extable.h>
#include <linux/ptrace.h>
#include <linux/sched.h>
#include <linux/sched/debug.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <linux/cpu.h>
#include <linux/entry-common.h>
#include <asm/fpu/api.h>
#include <asm/vtime.h>
#include "entry.h"
static inline void __user *get_trap_ip(struct pt_regs *regs)
{
unsigned long address;
if (regs->int_code & 0x200)
address = current->thread.trap_tdb.data[3];
else
address = regs->psw.addr;
return (void __user *) (address - (regs->int_code >> 16));
}
int is_valid_bugaddr(unsigned long addr)
{
return 1;
}
void do_report_trap(struct pt_regs *regs, int si_signo, int si_code, char *str)
{
if (user_mode(regs)) {
force_sig_fault(si_signo, si_code, get_trap_ip(regs));
report_user_fault(regs, si_signo, 0);
} else {
const struct exception_table_entry *fixup;
fixup = s390_search_extables(regs->psw.addr);
if (!fixup || !ex_handle(fixup, regs))
die(regs, str);
}
}
static void do_trap(struct pt_regs *regs, int si_signo, int si_code, char *str)
{
if (notify_die(DIE_TRAP, str, regs, 0,
regs->int_code, si_signo) == NOTIFY_STOP)
return;
do_report_trap(regs, si_signo, si_code, str);
}
NOKPROBE_SYMBOL(do_trap);
void do_per_trap(struct pt_regs *regs)
{
if (notify_die(DIE_SSTEP, "sstep", regs, 0, 0, SIGTRAP) == NOTIFY_STOP)
return;
if (!current->ptrace)
return;
force_sig_fault(SIGTRAP, TRAP_HWBKPT,
(void __force __user *) current->thread.per_event.address);
}
NOKPROBE_SYMBOL(do_per_trap);
static void default_trap_handler(struct pt_regs *regs)
{
if (user_mode(regs)) {
report_user_fault(regs, SIGSEGV, 0);
force_exit_sig(SIGSEGV);
} else
die(regs, "Unknown program exception");
}
#define DO_ERROR_INFO(name, signr, sicode, str) \
static void name(struct pt_regs *regs) \
{ \
do_trap(regs, signr, sicode, str); \
}
DO_ERROR_INFO(addressing_exception, SIGILL, ILL_ILLADR,
"addressing exception")
DO_ERROR_INFO(execute_exception, SIGILL, ILL_ILLOPN,
"execute exception")
DO_ERROR_INFO(divide_exception, SIGFPE, FPE_INTDIV,
"fixpoint divide exception")
DO_ERROR_INFO(overflow_exception, SIGFPE, FPE_INTOVF,
"fixpoint overflow exception")
DO_ERROR_INFO(hfp_overflow_exception, SIGFPE, FPE_FLTOVF,
"HFP overflow exception")
DO_ERROR_INFO(hfp_underflow_exception, SIGFPE, FPE_FLTUND,
"HFP underflow exception")
DO_ERROR_INFO(hfp_significance_exception, SIGFPE, FPE_FLTRES,
"HFP significance exception")
DO_ERROR_INFO(hfp_divide_exception, SIGFPE, FPE_FLTDIV,
"HFP divide exception")
DO_ERROR_INFO(hfp_sqrt_exception, SIGFPE, FPE_FLTINV,
"HFP square root exception")
DO_ERROR_INFO(operand_exception, SIGILL, ILL_ILLOPN,
"operand exception")
DO_ERROR_INFO(privileged_op, SIGILL, ILL_PRVOPC,
"privileged operation")
DO_ERROR_INFO(special_op_exception, SIGILL, ILL_ILLOPN,
"special operation exception")
DO_ERROR_INFO(transaction_exception, SIGILL, ILL_ILLOPN,
"transaction constraint exception")
static inline void do_fp_trap(struct pt_regs *regs, __u32 fpc)
{
int si_code = 0;
/* FPC[2] is Data Exception Code */
if ((fpc & 0x00000300) == 0) {
/* bits 6 and 7 of DXC are 0 iff IEEE exception */
if (fpc & 0x8000) /* invalid fp operation */
si_code = FPE_FLTINV;
else if (fpc & 0x4000) /* div by 0 */
si_code = FPE_FLTDIV;
else if (fpc & 0x2000) /* overflow */
si_code = FPE_FLTOVF;
else if (fpc & 0x1000) /* underflow */
si_code = FPE_FLTUND;
else if (fpc & 0x0800) /* inexact */
si_code = FPE_FLTRES;
}
do_trap(regs, SIGFPE, si_code, "floating point exception");
}
static void translation_exception(struct pt_regs *regs)
{
/* May never happen. */
panic("Translation exception");
}
static void illegal_op(struct pt_regs *regs)
{
__u8 opcode[6];
__u16 __user *location;
int is_uprobe_insn = 0;
int signal = 0;
location = get_trap_ip(regs);
if (user_mode(regs)) {
if (get_user(*((__u16 *) opcode), (__u16 __user *) location))
return;
if (*((__u16 *) opcode) == S390_BREAKPOINT_U16) {
if (current->ptrace)
force_sig_fault(SIGTRAP, TRAP_BRKPT, location);
else
signal = SIGILL;
#ifdef CONFIG_UPROBES
} else if (*((__u16 *) opcode) == UPROBE_SWBP_INSN) {
is_uprobe_insn = 1;
#endif
} else
signal = SIGILL;
}
/*
* We got either an illegal op in kernel mode, or user space trapped
* on a uprobes illegal instruction. See if kprobes or uprobes picks
* it up. If not, SIGILL.
*/
if (is_uprobe_insn || !user_mode(regs)) {
if (notify_die(DIE_BPT, "bpt", regs, 0,
3, SIGTRAP) != NOTIFY_STOP)
signal = SIGILL;
}
if (signal)
do_trap(regs, signal, ILL_ILLOPC, "illegal operation");
}
NOKPROBE_SYMBOL(illegal_op);
DO_ERROR_INFO(specification_exception, SIGILL, ILL_ILLOPN,
"specification exception");
static void vector_exception(struct pt_regs *regs)
{
int si_code, vic;
if (!MACHINE_HAS_VX) {
do_trap(regs, SIGILL, ILL_ILLOPN, "illegal operation");
return;
}
/* get vector interrupt code from fpc */
save_fpu_regs();
vic = (current->thread.fpu.fpc & 0xf00) >> 8;
switch (vic) {
case 1: /* invalid vector operation */
si_code = FPE_FLTINV;
break;
case 2: /* division by zero */
si_code = FPE_FLTDIV;
break;
case 3: /* overflow */
si_code = FPE_FLTOVF;
break;
case 4: /* underflow */
si_code = FPE_FLTUND;
break;
case 5: /* inexact */
si_code = FPE_FLTRES;
break;
default: /* unknown cause */
si_code = 0;
}
do_trap(regs, SIGFPE, si_code, "vector exception");
}
static void data_exception(struct pt_regs *regs)
{
save_fpu_regs();
if (current->thread.fpu.fpc & FPC_DXC_MASK)
do_fp_trap(regs, current->thread.fpu.fpc);
else
do_trap(regs, SIGILL, ILL_ILLOPN, "data exception");
}
static void space_switch_exception(struct pt_regs *regs)
{
/* Set user psw back to home space mode. */
if (user_mode(regs))
regs->psw.mask |= PSW_ASC_HOME;
/* Send SIGILL. */
do_trap(regs, SIGILL, ILL_PRVOPC, "space switch event");
}
static void monitor_event_exception(struct pt_regs *regs)
{
const struct exception_table_entry *fixup;
if (user_mode(regs))
return;
switch (report_bug(regs->psw.addr - (regs->int_code >> 16), regs)) {
case BUG_TRAP_TYPE_NONE:
fixup = s390_search_extables(regs->psw.addr);
if (fixup)
ex_handle(fixup, regs);
break;
case BUG_TRAP_TYPE_WARN:
break;
case BUG_TRAP_TYPE_BUG:
die(regs, "monitor event");
break;
}
}
void kernel_stack_overflow(struct pt_regs *regs)
{
bust_spinlocks(1);
printk("Kernel stack overflow.\n");
show_regs(regs);
bust_spinlocks(0);
panic("Corrupt kernel stack, can't continue.");
}
NOKPROBE_SYMBOL(kernel_stack_overflow);
static void __init test_monitor_call(void)
{
int val = 1;
if (!IS_ENABLED(CONFIG_BUG))
return;
asm volatile(
" mc 0,0\n"
"0: xgr %0,%0\n"
"1:\n"
EX_TABLE(0b,1b)
: "+d" (val));
if (!val)
panic("Monitor call doesn't work!\n");
}
void __init trap_init(void)
{
sort_extable(__start_amode31_ex_table, __stop_amode31_ex_table);
local_mcck_enable();
test_monitor_call();
}
static void (*pgm_check_table[128])(struct pt_regs *regs);
void noinstr __do_pgm_check(struct pt_regs *regs)
{
unsigned long last_break = S390_lowcore.breaking_event_addr;
unsigned int trapnr;
irqentry_state_t state;
regs->int_code = *(u32 *)&S390_lowcore.pgm_ilc;
regs->int_parm_long = S390_lowcore.trans_exc_code;
state = irqentry_enter(regs);
if (user_mode(regs)) {
update_timer_sys();
if (last_break < 4096)
last_break = 1;
current->thread.last_break = last_break;
regs->args[0] = last_break;
}
if (S390_lowcore.pgm_code & 0x0200) {
/* transaction abort */
current->thread.trap_tdb = S390_lowcore.pgm_tdb;
}
if (S390_lowcore.pgm_code & PGM_INT_CODE_PER) {
if (user_mode(regs)) {
struct per_event *ev = &current->thread.per_event;
set_thread_flag(TIF_PER_TRAP);
ev->address = S390_lowcore.per_address;
ev->cause = *(u16 *)&S390_lowcore.per_code;
ev->paid = S390_lowcore.per_access_id;
} else {
/* PER event in kernel is kprobes */
__arch_local_irq_ssm(regs->psw.mask & ~PSW_MASK_PER);
do_per_trap(regs);
goto out;
}
}
if (!irqs_disabled_flags(regs->psw.mask))
trace_hardirqs_on();
__arch_local_irq_ssm(regs->psw.mask & ~PSW_MASK_PER);
trapnr = regs->int_code & PGM_INT_CODE_MASK;
if (trapnr)
pgm_check_table[trapnr](regs);
out:
local_irq_disable();
irqentry_exit(regs, state);
}
/*
* The program check table contains exactly 128 (0x00-0x7f) entries. Each
* line defines the function to be called corresponding to the program check
* interruption code.
*/
static void (*pgm_check_table[128])(struct pt_regs *regs) = {
[0x00] = default_trap_handler,
[0x01] = illegal_op,
[0x02] = privileged_op,
[0x03] = execute_exception,
[0x04] = do_protection_exception,
[0x05] = addressing_exception,
[0x06] = specification_exception,
[0x07] = data_exception,
[0x08] = overflow_exception,
[0x09] = divide_exception,
[0x0a] = overflow_exception,
[0x0b] = divide_exception,
[0x0c] = hfp_overflow_exception,
[0x0d] = hfp_underflow_exception,
[0x0e] = hfp_significance_exception,
[0x0f] = hfp_divide_exception,
[0x10] = do_dat_exception,
[0x11] = do_dat_exception,
[0x12] = translation_exception,
[0x13] = special_op_exception,
[0x14] = default_trap_handler,
[0x15] = operand_exception,
[0x16] = default_trap_handler,
[0x17] = default_trap_handler,
[0x18] = transaction_exception,
[0x19] = default_trap_handler,
[0x1a] = default_trap_handler,
[0x1b] = vector_exception,
[0x1c] = space_switch_exception,
[0x1d] = hfp_sqrt_exception,
[0x1e ... 0x37] = default_trap_handler,
[0x38] = do_dat_exception,
[0x39] = do_dat_exception,
[0x3a] = do_dat_exception,
[0x3b] = do_dat_exception,
[0x3c] = default_trap_handler,
[0x3d] = do_secure_storage_access,
[0x3e] = do_non_secure_storage_access,
[0x3f] = do_secure_storage_violation,
[0x40] = monitor_event_exception,
[0x41 ... 0x7f] = default_trap_handler,
};
#define COND_TRAP(x) asm( \
".weak " __stringify(x) "\n\t" \
".set " __stringify(x) "," \
__stringify(default_trap_handler))
COND_TRAP(do_secure_storage_access);
COND_TRAP(do_non_secure_storage_access);
COND_TRAP(do_secure_storage_violation);
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