linux/lib/ubsan.c

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UBSAN: run-time undefined behavior sanity checker UBSAN uses compile-time instrumentation to catch undefined behavior (UB). Compiler inserts code that perform certain kinds of checks before operations that could cause UB. If check fails (i.e. UB detected) __ubsan_handle_* function called to print error message. So the most of the work is done by compiler. This patch just implements ubsan handlers printing errors. GCC has this capability since 4.9.x [1] (see -fsanitize=undefined option and its suboptions). However GCC 5.x has more checkers implemented [2]. Article [3] has a bit more details about UBSAN in the GCC. [1] - https://gcc.gnu.org/onlinedocs/gcc-4.9.0/gcc/Debugging-Options.html [2] - https://gcc.gnu.org/onlinedocs/gcc/Debugging-Options.html [3] - http://developerblog.redhat.com/2014/10/16/gcc-undefined-behavior-sanitizer-ubsan/ Issues which UBSAN has found thus far are: Found bugs: * out-of-bounds access - 97840cb67ff5 ("netfilter: nfnetlink: fix insufficient validation in nfnetlink_bind") undefined shifts: * d48458d4a768 ("jbd2: use a better hash function for the revoke table") * 10632008b9e1 ("clockevents: Prevent shift out of bounds") * 'x << -1' shift in ext4 - http://lkml.kernel.org/r/<5444EF21.8020501@samsung.com> * undefined rol32(0) - http://lkml.kernel.org/r/<1449198241-20654-1-git-send-email-sasha.levin@oracle.com> * undefined dirty_ratelimit calculation - http://lkml.kernel.org/r/<566594E2.3050306@odin.com> * undefined roundown_pow_of_two(0) - http://lkml.kernel.org/r/<1449156616-11474-1-git-send-email-sasha.levin@oracle.com> * [WONTFIX] undefined shift in __bpf_prog_run - http://lkml.kernel.org/r/<CACT4Y+ZxoR3UjLgcNdUm4fECLMx2VdtfrENMtRRCdgHB2n0bJA@mail.gmail.com> WONTFIX here because it should be fixed in bpf program, not in kernel. signed overflows: * 32a8df4e0b33f ("sched: Fix odd values in effective_load() calculations") * mul overflow in ntp - http://lkml.kernel.org/r/<1449175608-1146-1-git-send-email-sasha.levin@oracle.com> * incorrect conversion into rtc_time in rtc_time64_to_tm() - http://lkml.kernel.org/r/<1449187944-11730-1-git-send-email-sasha.levin@oracle.com> * unvalidated timespec in io_getevents() - http://lkml.kernel.org/r/<CACT4Y+bBxVYLQ6LtOKrKtnLthqLHcw-BMp3aqP3mjdAvr9FULQ@mail.gmail.com> * [NOTABUG] signed overflow in ktime_add_safe() - http://lkml.kernel.org/r/<CACT4Y+aJ4muRnWxsUe1CMnA6P8nooO33kwG-c8YZg=0Xc8rJqw@mail.gmail.com> [akpm@linux-foundation.org: fix unused local warning] [akpm@linux-foundation.org: fix __int128 build woes] Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Sasha Levin <sasha.levin@oracle.com> Cc: Randy Dunlap <rdunlap@infradead.org> Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Michal Marek <mmarek@suse.cz> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Yury Gribov <y.gribov@samsung.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Konstantin Khlebnikov <koct9i@gmail.com> Cc: Kostya Serebryany <kcc@google.com> Cc: Johannes Berg <johannes@sipsolutions.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-01-20 23:00:55 +00:00
/*
* UBSAN error reporting functions
*
* Copyright (c) 2014 Samsung Electronics Co., Ltd.
* Author: Andrey Ryabinin <ryabinin.a.a@gmail.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
*/
#include <linux/bitops.h>
#include <linux/bug.h>
#include <linux/ctype.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/sched.h>
#include "ubsan.h"
const char *type_check_kinds[] = {
"load of",
"store to",
"reference binding to",
"member access within",
"member call on",
"constructor call on",
"downcast of",
"downcast of"
};
#define REPORTED_BIT 31
#if (BITS_PER_LONG == 64) && defined(__BIG_ENDIAN)
#define COLUMN_MASK (~(1U << REPORTED_BIT))
#define LINE_MASK (~0U)
#else
#define COLUMN_MASK (~0U)
#define LINE_MASK (~(1U << REPORTED_BIT))
#endif
#define VALUE_LENGTH 40
static bool was_reported(struct source_location *location)
{
return test_and_set_bit(REPORTED_BIT, &location->reported);
}
static void print_source_location(const char *prefix,
struct source_location *loc)
{
pr_err("%s %s:%d:%d\n", prefix, loc->file_name,
loc->line & LINE_MASK, loc->column & COLUMN_MASK);
}
static bool suppress_report(struct source_location *loc)
{
return current->in_ubsan || was_reported(loc);
}
static bool type_is_int(struct type_descriptor *type)
{
return type->type_kind == type_kind_int;
}
static bool type_is_signed(struct type_descriptor *type)
{
WARN_ON(!type_is_int(type));
return type->type_info & 1;
}
static unsigned type_bit_width(struct type_descriptor *type)
{
return 1 << (type->type_info >> 1);
}
static bool is_inline_int(struct type_descriptor *type)
{
unsigned inline_bits = sizeof(unsigned long)*8;
unsigned bits = type_bit_width(type);
WARN_ON(!type_is_int(type));
return bits <= inline_bits;
}
static s_max get_signed_val(struct type_descriptor *type, unsigned long val)
{
if (is_inline_int(type)) {
unsigned extra_bits = sizeof(s_max)*8 - type_bit_width(type);
return ((s_max)val) << extra_bits >> extra_bits;
}
if (type_bit_width(type) == 64)
return *(s64 *)val;
return *(s_max *)val;
}
static bool val_is_negative(struct type_descriptor *type, unsigned long val)
{
return type_is_signed(type) && get_signed_val(type, val) < 0;
}
static u_max get_unsigned_val(struct type_descriptor *type, unsigned long val)
{
if (is_inline_int(type))
return val;
if (type_bit_width(type) == 64)
return *(u64 *)val;
return *(u_max *)val;
}
static void val_to_string(char *str, size_t size, struct type_descriptor *type,
unsigned long value)
{
if (type_is_int(type)) {
if (type_bit_width(type) == 128) {
#if defined(CONFIG_ARCH_SUPPORTS_INT128) && defined(__SIZEOF_INT128__)
u_max val = get_unsigned_val(type, value);
scnprintf(str, size, "0x%08x%08x%08x%08x",
(u32)(val >> 96),
(u32)(val >> 64),
(u32)(val >> 32),
(u32)(val));
#else
WARN_ON(1);
#endif
} else if (type_is_signed(type)) {
scnprintf(str, size, "%lld",
(s64)get_signed_val(type, value));
} else {
scnprintf(str, size, "%llu",
(u64)get_unsigned_val(type, value));
}
}
}
static bool location_is_valid(struct source_location *loc)
{
return loc->file_name != NULL;
}
static DEFINE_SPINLOCK(report_lock);
static void ubsan_prologue(struct source_location *location,
unsigned long *flags)
{
current->in_ubsan++;
spin_lock_irqsave(&report_lock, *flags);
pr_err("========================================"
"========================================\n");
print_source_location("UBSAN: Undefined behaviour in", location);
}
static void ubsan_epilogue(unsigned long *flags)
{
dump_stack();
pr_err("========================================"
"========================================\n");
spin_unlock_irqrestore(&report_lock, *flags);
current->in_ubsan--;
}
static void handle_overflow(struct overflow_data *data, unsigned long lhs,
unsigned long rhs, char op)
{
struct type_descriptor *type = data->type;
unsigned long flags;
char lhs_val_str[VALUE_LENGTH];
char rhs_val_str[VALUE_LENGTH];
if (suppress_report(&data->location))
return;
ubsan_prologue(&data->location, &flags);
val_to_string(lhs_val_str, sizeof(lhs_val_str), type, lhs);
val_to_string(rhs_val_str, sizeof(rhs_val_str), type, rhs);
pr_err("%s integer overflow:\n",
type_is_signed(type) ? "signed" : "unsigned");
pr_err("%s %c %s cannot be represented in type %s\n",
lhs_val_str,
op,
rhs_val_str,
type->type_name);
ubsan_epilogue(&flags);
}
void __ubsan_handle_add_overflow(struct overflow_data *data,
unsigned long lhs,
unsigned long rhs)
{
handle_overflow(data, lhs, rhs, '+');
}
EXPORT_SYMBOL(__ubsan_handle_add_overflow);
void __ubsan_handle_sub_overflow(struct overflow_data *data,
unsigned long lhs,
unsigned long rhs)
{
handle_overflow(data, lhs, rhs, '-');
}
EXPORT_SYMBOL(__ubsan_handle_sub_overflow);
void __ubsan_handle_mul_overflow(struct overflow_data *data,
unsigned long lhs,
unsigned long rhs)
{
handle_overflow(data, lhs, rhs, '*');
}
EXPORT_SYMBOL(__ubsan_handle_mul_overflow);
void __ubsan_handle_negate_overflow(struct overflow_data *data,
unsigned long old_val)
{
unsigned long flags;
char old_val_str[VALUE_LENGTH];
if (suppress_report(&data->location))
return;
ubsan_prologue(&data->location, &flags);
val_to_string(old_val_str, sizeof(old_val_str), data->type, old_val);
pr_err("negation of %s cannot be represented in type %s:\n",
old_val_str, data->type->type_name);
ubsan_epilogue(&flags);
}
EXPORT_SYMBOL(__ubsan_handle_negate_overflow);
void __ubsan_handle_divrem_overflow(struct overflow_data *data,
unsigned long lhs,
unsigned long rhs)
{
unsigned long flags;
char rhs_val_str[VALUE_LENGTH];
if (suppress_report(&data->location))
return;
ubsan_prologue(&data->location, &flags);
val_to_string(rhs_val_str, sizeof(rhs_val_str), data->type, rhs);
if (type_is_signed(data->type) && get_signed_val(data->type, rhs) == -1)
pr_err("division of %s by -1 cannot be represented in type %s\n",
rhs_val_str, data->type->type_name);
else
pr_err("division by zero\n");
ubsan_epilogue(&flags);
}
EXPORT_SYMBOL(__ubsan_handle_divrem_overflow);
static void handle_null_ptr_deref(struct type_mismatch_data *data)
{
unsigned long flags;
if (suppress_report(&data->location))
return;
ubsan_prologue(&data->location, &flags);
pr_err("%s null pointer of type %s\n",
type_check_kinds[data->type_check_kind],
data->type->type_name);
ubsan_epilogue(&flags);
}
static void handle_missaligned_access(struct type_mismatch_data *data,
unsigned long ptr)
{
unsigned long flags;
if (suppress_report(&data->location))
return;
ubsan_prologue(&data->location, &flags);
pr_err("%s misaligned address %p for type %s\n",
type_check_kinds[data->type_check_kind],
(void *)ptr, data->type->type_name);
pr_err("which requires %ld byte alignment\n", data->alignment);
ubsan_epilogue(&flags);
}
static void handle_object_size_mismatch(struct type_mismatch_data *data,
unsigned long ptr)
{
unsigned long flags;
if (suppress_report(&data->location))
return;
ubsan_prologue(&data->location, &flags);
pr_err("%s address %pk with insufficient space\n",
type_check_kinds[data->type_check_kind],
(void *) ptr);
pr_err("for an object of type %s\n", data->type->type_name);
ubsan_epilogue(&flags);
}
void __ubsan_handle_type_mismatch(struct type_mismatch_data *data,
unsigned long ptr)
{
if (!ptr)
handle_null_ptr_deref(data);
else if (data->alignment && !IS_ALIGNED(ptr, data->alignment))
handle_missaligned_access(data, ptr);
else
handle_object_size_mismatch(data, ptr);
}
EXPORT_SYMBOL(__ubsan_handle_type_mismatch);
void __ubsan_handle_nonnull_return(struct nonnull_return_data *data)
{
unsigned long flags;
if (suppress_report(&data->location))
return;
ubsan_prologue(&data->location, &flags);
pr_err("null pointer returned from function declared to never return null\n");
if (location_is_valid(&data->attr_location))
print_source_location("returns_nonnull attribute specified in",
&data->attr_location);
ubsan_epilogue(&flags);
}
EXPORT_SYMBOL(__ubsan_handle_nonnull_return);
void __ubsan_handle_vla_bound_not_positive(struct vla_bound_data *data,
unsigned long bound)
{
unsigned long flags;
char bound_str[VALUE_LENGTH];
if (suppress_report(&data->location))
return;
ubsan_prologue(&data->location, &flags);
val_to_string(bound_str, sizeof(bound_str), data->type, bound);
pr_err("variable length array bound value %s <= 0\n", bound_str);
ubsan_epilogue(&flags);
}
EXPORT_SYMBOL(__ubsan_handle_vla_bound_not_positive);
void __ubsan_handle_out_of_bounds(struct out_of_bounds_data *data,
unsigned long index)
{
unsigned long flags;
char index_str[VALUE_LENGTH];
if (suppress_report(&data->location))
return;
ubsan_prologue(&data->location, &flags);
val_to_string(index_str, sizeof(index_str), data->index_type, index);
pr_err("index %s is out of range for type %s\n", index_str,
data->array_type->type_name);
ubsan_epilogue(&flags);
}
EXPORT_SYMBOL(__ubsan_handle_out_of_bounds);
void __ubsan_handle_shift_out_of_bounds(struct shift_out_of_bounds_data *data,
unsigned long lhs, unsigned long rhs)
{
unsigned long flags;
struct type_descriptor *rhs_type = data->rhs_type;
struct type_descriptor *lhs_type = data->lhs_type;
char rhs_str[VALUE_LENGTH];
char lhs_str[VALUE_LENGTH];
if (suppress_report(&data->location))
return;
ubsan_prologue(&data->location, &flags);
val_to_string(rhs_str, sizeof(rhs_str), rhs_type, rhs);
val_to_string(lhs_str, sizeof(lhs_str), lhs_type, lhs);
if (val_is_negative(rhs_type, rhs))
pr_err("shift exponent %s is negative\n", rhs_str);
else if (get_unsigned_val(rhs_type, rhs) >=
type_bit_width(lhs_type))
pr_err("shift exponent %s is too large for %u-bit type %s\n",
rhs_str,
type_bit_width(lhs_type),
lhs_type->type_name);
else if (val_is_negative(lhs_type, lhs))
pr_err("left shift of negative value %s\n",
lhs_str);
else
pr_err("left shift of %s by %s places cannot be"
" represented in type %s\n",
lhs_str, rhs_str,
lhs_type->type_name);
ubsan_epilogue(&flags);
}
EXPORT_SYMBOL(__ubsan_handle_shift_out_of_bounds);
void __noreturn
__ubsan_handle_builtin_unreachable(struct unreachable_data *data)
{
unsigned long flags;
ubsan_prologue(&data->location, &flags);
pr_err("calling __builtin_unreachable()\n");
ubsan_epilogue(&flags);
panic("can't return from __builtin_unreachable()");
}
EXPORT_SYMBOL(__ubsan_handle_builtin_unreachable);
void __ubsan_handle_load_invalid_value(struct invalid_value_data *data,
unsigned long val)
{
unsigned long flags;
char val_str[VALUE_LENGTH];
if (suppress_report(&data->location))
return;
ubsan_prologue(&data->location, &flags);
val_to_string(val_str, sizeof(val_str), data->type, val);
pr_err("load of value %s is not a valid value for type %s\n",
val_str, data->type->type_name);
ubsan_epilogue(&flags);
}
EXPORT_SYMBOL(__ubsan_handle_load_invalid_value);