linux-stable/lib/ubsan.c
Andrey Ryabinin 6aaa31aeb9 ubsan: remove overflow checks
Since GCC 8.0 -fsanitize=signed-integer-overflow doesn't work with
-fwrapv.  -fwrapv makes signed overflows defines and GCC essentially
disables ubsan checks.  On GCC < 8.0 -fwrapv doesn't have influence on
-fsanitize=signed-integer-overflow setting, so it kinda works but
generates false-positves and violates uaccess rules:

lib/iov_iter.o: warning: objtool: iovec_from_user()+0x22d: call to
__ubsan_handle_add_overflow() with UACCESS enabled

Disable signed overflow checks to avoid these problems.  Remove unsigned
overflow checks as well.  Unsigned overflow appeared as side effect of
commit cdf8a76fda ("ubsan: move cc-option tests into Kconfig"), but it
never worked (kernel doesn't boot).  And unsigned overflows are allowed by
C standard, so it just pointless.

Link: https://lkml.kernel.org/r/20210209232348.20510-1-ryabinin.a.a@gmail.com
Signed-off-by: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-02-26 09:41:05 -08:00

392 lines
9.9 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
/*
* UBSAN error reporting functions
*
* Copyright (c) 2014 Samsung Electronics Co., Ltd.
* Author: Andrey Ryabinin <ryabinin.a.a@gmail.com>
*/
#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 <linux/uaccess.h>
#include "ubsan.h"
static const char * const 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 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, void *val)
{
if (is_inline_int(type)) {
unsigned extra_bits = sizeof(s_max)*8 - type_bit_width(type);
unsigned long ulong_val = (unsigned long)val;
return ((s_max)ulong_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, void *val)
{
return type_is_signed(type) && get_signed_val(type, val) < 0;
}
static u_max get_unsigned_val(struct type_descriptor *type, void *val)
{
if (is_inline_int(type))
return (unsigned long)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,
void *value)
{
if (type_is_int(type)) {
if (type_bit_width(type) == 128) {
#if defined(CONFIG_ARCH_SUPPORTS_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 void ubsan_prologue(struct source_location *loc, const char *reason)
{
current->in_ubsan++;
pr_err("========================================"
"========================================\n");
pr_err("UBSAN: %s in %s:%d:%d\n", reason, loc->file_name,
loc->line & LINE_MASK, loc->column & COLUMN_MASK);
}
static void ubsan_epilogue(void)
{
dump_stack();
pr_err("========================================"
"========================================\n");
current->in_ubsan--;
if (panic_on_warn) {
/*
* This thread may hit another WARN() in the panic path.
* Resetting this prevents additional WARN() from panicking the
* system on this thread. Other threads are blocked by the
* panic_mutex in panic().
*/
panic_on_warn = 0;
panic("panic_on_warn set ...\n");
}
}
void __ubsan_handle_divrem_overflow(void *_data, void *lhs, void *rhs)
{
struct overflow_data *data = _data;
char rhs_val_str[VALUE_LENGTH];
if (suppress_report(&data->location))
return;
ubsan_prologue(&data->location, "division-overflow");
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();
}
EXPORT_SYMBOL(__ubsan_handle_divrem_overflow);
static void handle_null_ptr_deref(struct type_mismatch_data_common *data)
{
if (suppress_report(data->location))
return;
ubsan_prologue(data->location, "null-ptr-deref");
pr_err("%s null pointer of type %s\n",
type_check_kinds[data->type_check_kind],
data->type->type_name);
ubsan_epilogue();
}
static void handle_misaligned_access(struct type_mismatch_data_common *data,
unsigned long ptr)
{
if (suppress_report(data->location))
return;
ubsan_prologue(data->location, "misaligned-access");
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();
}
static void handle_object_size_mismatch(struct type_mismatch_data_common *data,
unsigned long ptr)
{
if (suppress_report(data->location))
return;
ubsan_prologue(data->location, "object-size-mismatch");
pr_err("%s address %p 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();
}
static void ubsan_type_mismatch_common(struct type_mismatch_data_common *data,
unsigned long ptr)
{
unsigned long flags = user_access_save();
if (!ptr)
handle_null_ptr_deref(data);
else if (data->alignment && !IS_ALIGNED(ptr, data->alignment))
handle_misaligned_access(data, ptr);
else
handle_object_size_mismatch(data, ptr);
user_access_restore(flags);
}
void __ubsan_handle_type_mismatch(struct type_mismatch_data *data,
void *ptr)
{
struct type_mismatch_data_common common_data = {
.location = &data->location,
.type = data->type,
.alignment = data->alignment,
.type_check_kind = data->type_check_kind
};
ubsan_type_mismatch_common(&common_data, (unsigned long)ptr);
}
EXPORT_SYMBOL(__ubsan_handle_type_mismatch);
void __ubsan_handle_type_mismatch_v1(void *_data, void *ptr)
{
struct type_mismatch_data_v1 *data = _data;
struct type_mismatch_data_common common_data = {
.location = &data->location,
.type = data->type,
.alignment = 1UL << data->log_alignment,
.type_check_kind = data->type_check_kind
};
ubsan_type_mismatch_common(&common_data, (unsigned long)ptr);
}
EXPORT_SYMBOL(__ubsan_handle_type_mismatch_v1);
void __ubsan_handle_out_of_bounds(void *_data, void *index)
{
struct out_of_bounds_data *data = _data;
char index_str[VALUE_LENGTH];
if (suppress_report(&data->location))
return;
ubsan_prologue(&data->location, "array-index-out-of-bounds");
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();
}
EXPORT_SYMBOL(__ubsan_handle_out_of_bounds);
void __ubsan_handle_shift_out_of_bounds(void *_data, void *lhs, void *rhs)
{
struct shift_out_of_bounds_data *data = _data;
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];
unsigned long ua_flags = user_access_save();
if (suppress_report(&data->location))
goto out;
ubsan_prologue(&data->location, "shift-out-of-bounds");
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();
out:
user_access_restore(ua_flags);
}
EXPORT_SYMBOL(__ubsan_handle_shift_out_of_bounds);
void __ubsan_handle_builtin_unreachable(void *_data)
{
struct unreachable_data *data = _data;
ubsan_prologue(&data->location, "unreachable");
pr_err("calling __builtin_unreachable()\n");
ubsan_epilogue();
panic("can't return from __builtin_unreachable()");
}
EXPORT_SYMBOL(__ubsan_handle_builtin_unreachable);
void __ubsan_handle_load_invalid_value(void *_data, void *val)
{
struct invalid_value_data *data = _data;
char val_str[VALUE_LENGTH];
if (suppress_report(&data->location))
return;
ubsan_prologue(&data->location, "invalid-load");
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();
}
EXPORT_SYMBOL(__ubsan_handle_load_invalid_value);
void __ubsan_handle_alignment_assumption(void *_data, unsigned long ptr,
unsigned long align,
unsigned long offset);
void __ubsan_handle_alignment_assumption(void *_data, unsigned long ptr,
unsigned long align,
unsigned long offset)
{
struct alignment_assumption_data *data = _data;
unsigned long real_ptr;
if (suppress_report(&data->location))
return;
ubsan_prologue(&data->location, "alignment-assumption");
if (offset)
pr_err("assumption of %lu byte alignment (with offset of %lu byte) for pointer of type %s failed",
align, offset, data->type->type_name);
else
pr_err("assumption of %lu byte alignment for pointer of type %s failed",
align, data->type->type_name);
real_ptr = ptr - offset;
pr_err("%saddress is %lu aligned, misalignment offset is %lu bytes",
offset ? "offset " : "", BIT(real_ptr ? __ffs(real_ptr) : 0),
real_ptr & (align - 1));
ubsan_epilogue();
}
EXPORT_SYMBOL(__ubsan_handle_alignment_assumption);