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runtime safety check for casting null to pointer

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see #1059
This commit is contained in:
Andrew Kelley 2019-02-14 01:09:33 -05:00
parent d4d2718bca
commit 59de24817e
No known key found for this signature in database
GPG Key ID: 7C5F548F728501A9
6 changed files with 67 additions and 27 deletions
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3
src/all_types.hpp
View File

@ -1488,6 +1488,7 @@ enum PanicMsgId {
PanicMsgIdBadUnionField,
PanicMsgIdBadEnumValue,
PanicMsgIdFloatToInt,
PanicMsgIdPtrCastNull,
PanicMsgIdCount,
};
@ -3001,12 +3002,14 @@ struct IrInstructionPtrCastSrc {
IrInstruction *dest_type;
IrInstruction *ptr;
bool safety_check_on;
};
struct IrInstructionPtrCastGen {
IrInstruction base;
IrInstruction *ptr;
bool safety_check_on;
};
struct IrInstructionBitCast {

9
src/analyze.cpp
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@ -6902,3 +6902,12 @@ const char *container_string(ContainerKind kind) {
}
zig_unreachable();
}
bool ptr_allows_addr_zero(ZigType *ptr_type) {
if (ptr_type->id == ZigTypeIdPointer) {
return ptr_type->data.pointer.allow_zero;
} else if (ptr_type->id == ZigTypeIdOptional) {
return true;
}
return false;
}

1
src/analyze.hpp
View File

@ -45,6 +45,7 @@ void find_libc_lib_path(CodeGen *g);
bool type_has_bits(ZigType *type_entry);
bool type_allowed_in_extern(CodeGen *g, ZigType *type_entry);
bool ptr_allows_addr_zero(ZigType *ptr_type);
ImportTableEntry *add_source_file(CodeGen *g, PackageTableEntry *package, Buf *abs_full_path, Buf *source_code);

19
src/codegen.cpp
View File

@ -950,6 +950,8 @@ static Buf *panic_msg_buf(PanicMsgId msg_id) {
return buf_create_from_str("invalid enum value");
case PanicMsgIdFloatToInt:
return buf_create_from_str("integer part of floating point value out of bounds");
case PanicMsgIdPtrCastNull:
return buf_create_from_str("cast causes pointer to be null");
}
zig_unreachable();
}
@ -3028,7 +3030,22 @@ static LLVMValueRef ir_render_ptr_cast(CodeGen *g, IrExecutable *executable,
return nullptr;
}
LLVMValueRef ptr = ir_llvm_value(g, instruction->ptr);
return LLVMBuildBitCast(g->builder, ptr, wanted_type->type_ref, "");
LLVMValueRef result_ptr = LLVMBuildBitCast(g->builder, ptr, wanted_type->type_ref, "");
bool want_safety_check = instruction->safety_check_on && ir_want_runtime_safety(g, &instruction->base);
if (!want_safety_check || ptr_allows_addr_zero(wanted_type))
return result_ptr;
LLVMValueRef zero = LLVMConstNull(LLVMTypeOf(result_ptr));
LLVMValueRef ok_bit = LLVMBuildICmp(g->builder, LLVMIntNE, result_ptr, zero, "");
LLVMBasicBlockRef fail_block = LLVMAppendBasicBlock(g->cur_fn_val, "PtrCastFail");
LLVMBasicBlockRef ok_block = LLVMAppendBasicBlock(g->cur_fn_val, "PtrCastOk");
LLVMBuildCondBr(g->builder, ok_bit, ok_block, fail_block);
LLVMPositionBuilderAtEnd(g->builder, fail_block);
gen_safety_crash(g, PanicMsgIdPtrCastNull);
LLVMPositionBuilderAtEnd(g->builder, ok_block);
return result_ptr;
}
static LLVMValueRef ir_render_bit_cast(CodeGen *g, IrExecutable *executable,

52
src/ir.cpp
View File

@ -172,7 +172,7 @@ static void buf_write_value_bytes(CodeGen *codegen, uint8_t *buf, ConstExprValue
static Error ir_read_const_ptr(IrAnalyze *ira, CodeGen *codegen, AstNode *source_node,
ConstExprValue *out_val, ConstExprValue *ptr_val);
static IrInstruction *ir_analyze_ptr_cast(IrAnalyze *ira, IrInstruction *source_instr, IrInstruction *ptr,
ZigType *dest_type, IrInstruction *dest_type_src);
ZigType *dest_type, IrInstruction *dest_type_src, bool safety_check_on);
static ConstExprValue *ir_resolve_const(IrAnalyze *ira, IrInstruction *value, UndefAllowed undef_allowed);
static void copy_const_val(ConstExprValue *dest, ConstExprValue *src, bool same_global_refs);
static Error resolve_ptr_align(IrAnalyze *ira, ZigType *ty, uint32_t *result_align);
@ -2202,12 +2202,13 @@ static IrInstruction *ir_build_test_comptime(IrBuilder *irb, Scope *scope, AstNo
}
static IrInstruction *ir_build_ptr_cast_src(IrBuilder *irb, Scope *scope, AstNode *source_node,
IrInstruction *dest_type, IrInstruction *ptr)
IrInstruction *dest_type, IrInstruction *ptr, bool safety_check_on)
{
IrInstructionPtrCastSrc *instruction = ir_build_instruction<IrInstructionPtrCastSrc>(
irb, scope, source_node);
instruction->dest_type = dest_type;
instruction->ptr = ptr;
instruction->safety_check_on = safety_check_on;
ir_ref_instruction(dest_type, irb->current_basic_block);
ir_ref_instruction(ptr, irb->current_basic_block);
@ -2216,12 +2217,13 @@ static IrInstruction *ir_build_ptr_cast_src(IrBuilder *irb, Scope *scope, AstNod
}
static IrInstruction *ir_build_ptr_cast_gen(IrAnalyze *ira, IrInstruction *source_instruction,
ZigType *ptr_type, IrInstruction *ptr)
ZigType *ptr_type, IrInstruction *ptr, bool safety_check_on)
{
IrInstructionPtrCastGen *instruction = ir_build_instruction<IrInstructionPtrCastGen>(
&ira->new_irb, source_instruction->scope, source_instruction->source_node);
instruction->base.value.type = ptr_type;
instruction->ptr = ptr;
instruction->safety_check_on = safety_check_on;
ir_ref_instruction(ptr, ira->new_irb.current_basic_block);
@ -4505,7 +4507,7 @@ static IrInstruction *ir_gen_builtin_fn_call(IrBuilder *irb, Scope *scope, AstNo
if (arg1_value == irb->codegen->invalid_instruction)
return arg1_value;
IrInstruction *ptr_cast = ir_build_ptr_cast_src(irb, scope, node, arg0_value, arg1_value);
IrInstruction *ptr_cast = ir_build_ptr_cast_src(irb, scope, node, arg0_value, arg1_value, true);
return ir_lval_wrap(irb, scope, ptr_cast, lval);
}
case BuiltinFnIdBitCast:
@ -6740,7 +6742,8 @@ static IrInstruction *ir_gen_cancel_target(IrBuilder *irb, Scope *scope, AstNode
IrInstruction *is_suspended_mask = ir_build_const_usize(irb, scope, node, 0x2); // 0b010
// TODO relies on Zig not re-ordering fields
IrInstruction *casted_target_inst = ir_build_ptr_cast_src(irb, scope, node, promise_T_type_val, target_inst);
IrInstruction *casted_target_inst = ir_build_ptr_cast_src(irb, scope, node, promise_T_type_val, target_inst,
false);
IrInstruction *coro_promise_ptr = ir_build_coro_promise(irb, scope, node, casted_target_inst);
Buf *atomic_state_field_name = buf_create_from_str(ATOMIC_STATE_FIELD_NAME);
IrInstruction *atomic_state_ptr = ir_build_field_ptr(irb, scope, node, coro_promise_ptr,
@ -6818,7 +6821,8 @@ static IrInstruction *ir_gen_resume_target(IrBuilder *irb, Scope *scope, AstNode
get_promise_type(irb->codegen, irb->codegen->builtin_types.entry_void));
// TODO relies on Zig not re-ordering fields
IrInstruction *casted_target_inst = ir_build_ptr_cast_src(irb, scope, node, promise_T_type_val, target_inst);
IrInstruction *casted_target_inst = ir_build_ptr_cast_src(irb, scope, node, promise_T_type_val, target_inst,
false);
IrInstruction *coro_promise_ptr = ir_build_coro_promise(irb, scope, node, casted_target_inst);
Buf *atomic_state_field_name = buf_create_from_str(ATOMIC_STATE_FIELD_NAME);
IrInstruction *atomic_state_ptr = ir_build_field_ptr(irb, scope, node, coro_promise_ptr,
@ -7363,7 +7367,8 @@ bool ir_gen(CodeGen *codegen, AstNode *node, Scope *scope, IrExecutable *ir_exec
u8_ptr_type = ir_build_const_type(irb, coro_scope, node,
get_pointer_to_type(irb->codegen, irb->codegen->builtin_types.entry_u8, false));
IrInstruction *promise_as_u8_ptr = ir_build_ptr_cast_src(irb, coro_scope, node, u8_ptr_type, coro_promise_ptr);
IrInstruction *promise_as_u8_ptr = ir_build_ptr_cast_src(irb, coro_scope, node, u8_ptr_type,
coro_promise_ptr, false);
coro_id = ir_build_coro_id(irb, coro_scope, node, promise_as_u8_ptr);
coro_size_var = ir_create_var(irb, node, coro_scope, nullptr, false, false, true, const_bool_false);
IrInstruction *coro_size = ir_build_coro_size(irb, coro_scope, node);
@ -7387,7 +7392,8 @@ bool ir_gen(CodeGen *codegen, AstNode *node, Scope *scope, IrExecutable *ir_exec
ir_build_return(irb, coro_scope, node, undef);
ir_set_cursor_at_end_and_append_block(irb, alloc_ok_block);
IrInstruction *coro_mem_ptr = ir_build_ptr_cast_src(irb, coro_scope, node, u8_ptr_type, maybe_coro_mem_ptr);
IrInstruction *coro_mem_ptr = ir_build_ptr_cast_src(irb, coro_scope, node, u8_ptr_type, maybe_coro_mem_ptr,
false);
irb->exec->coro_handle = ir_build_coro_begin(irb, coro_scope, node, coro_id, coro_mem_ptr);
Buf *atomic_state_field_name = buf_create_from_str(ATOMIC_STATE_FIELD_NAME);
@ -7465,9 +7471,10 @@ bool ir_gen(CodeGen *codegen, AstNode *node, Scope *scope, IrExecutable *ir_exec
get_pointer_to_type_extra(irb->codegen, irb->codegen->builtin_types.entry_u8,
false, false, PtrLenUnknown, 0, 0, 0));
IrInstruction *result_ptr = ir_build_load_ptr(irb, scope, node, irb->exec->coro_result_ptr_field_ptr);
IrInstruction *result_ptr_as_u8_ptr = ir_build_ptr_cast_src(irb, scope, node, u8_ptr_type_unknown_len, result_ptr);
IrInstruction *return_value_ptr_as_u8_ptr = ir_build_ptr_cast_src(irb, scope, node, u8_ptr_type_unknown_len,
irb->exec->coro_result_field_ptr);
IrInstruction *result_ptr_as_u8_ptr = ir_build_ptr_cast_src(irb, scope, node, u8_ptr_type_unknown_len,
result_ptr, false);
IrInstruction *return_value_ptr_as_u8_ptr = ir_build_ptr_cast_src(irb, scope, node,
u8_ptr_type_unknown_len, irb->exec->coro_result_field_ptr, false);
IrInstruction *return_type_inst = ir_build_const_type(irb, scope, node,
fn_entry->type_entry->data.fn.fn_type_id.return_type);
IrInstruction *size_of_ret_val = ir_build_size_of(irb, scope, node, return_type_inst);
@ -7517,7 +7524,8 @@ bool ir_gen(CodeGen *codegen, AstNode *node, Scope *scope, IrExecutable *ir_exec
IrInstruction *u8_ptr_type_unknown_len = ir_build_const_type(irb, scope, node,
get_pointer_to_type_extra(irb->codegen, irb->codegen->builtin_types.entry_u8,
false, false, PtrLenUnknown, 0, 0, 0));
IrInstruction *coro_mem_ptr = ir_build_ptr_cast_src(irb, scope, node, u8_ptr_type_unknown_len, coro_mem_ptr_maybe);
IrInstruction *coro_mem_ptr = ir_build_ptr_cast_src(irb, scope, node, u8_ptr_type_unknown_len,
coro_mem_ptr_maybe, false);
IrInstruction *coro_mem_ptr_ref = ir_build_ref(irb, scope, node, coro_mem_ptr, true, false);
IrInstruction *coro_size_ptr = ir_build_var_ptr(irb, scope, node, coro_size_var);
IrInstruction *coro_size = ir_build_load_ptr(irb, scope, node, coro_size_ptr);
@ -8644,15 +8652,6 @@ static ZigType *get_error_set_intersection(IrAnalyze *ira, ZigType *set1, ZigTyp
return err_set_type;
}
static bool ptr_allows_addr_zero(ZigType *ptr_type) {
if (ptr_type->id == ZigTypeIdPointer) {
return ptr_type->data.pointer.allow_zero;
} else if (ptr_type->id == ZigTypeIdOptional) {
return true;
}
return false;
}
static ConstCastOnly types_match_const_cast_only(IrAnalyze *ira, ZigType *wanted_type,
ZigType *actual_type, AstNode *source_node, bool wanted_is_mutable)
{
@ -11310,7 +11309,7 @@ static IrInstruction *ir_analyze_cast(IrAnalyze *ira, IrInstruction *source_inst
actual_type->data.pointer.host_int_bytes == dest_ptr_type->data.pointer.host_int_bytes &&
get_ptr_align(ira->codegen, actual_type) >= get_ptr_align(ira->codegen, dest_ptr_type))
{
return ir_analyze_ptr_cast(ira, source_instr, value, wanted_type, source_instr);
return ir_analyze_ptr_cast(ira, source_instr, value, wanted_type, source_instr, true);
}
}
@ -11352,7 +11351,7 @@ static IrInstruction *ir_analyze_cast(IrAnalyze *ira, IrInstruction *source_inst
actual_type->data.pointer.child_type, source_node,
!wanted_type->data.pointer.is_const).id == ConstCastResultIdOk)
{
return ir_analyze_ptr_cast(ira, source_instr, value, wanted_type, source_instr);
return ir_analyze_ptr_cast(ira, source_instr, value, wanted_type, source_instr, true);
}
// cast from integer to C pointer
@ -20616,7 +20615,7 @@ static IrInstruction *ir_align_cast(IrAnalyze *ira, IrInstruction *target, uint3
}
static IrInstruction *ir_analyze_ptr_cast(IrAnalyze *ira, IrInstruction *source_instr, IrInstruction *ptr,
ZigType *dest_type, IrInstruction *dest_type_src)
ZigType *dest_type, IrInstruction *dest_type_src, bool safety_check_on)
{
Error err;
@ -20685,7 +20684,7 @@ static IrInstruction *ir_analyze_ptr_cast(IrAnalyze *ira, IrInstruction *source_
return ira->codegen->invalid_instruction;
}
IrInstruction *casted_ptr = ir_build_ptr_cast_gen(ira, source_instr, dest_type, ptr);
IrInstruction *casted_ptr = ir_build_ptr_cast_gen(ira, source_instr, dest_type, ptr, safety_check_on);
if (type_has_bits(dest_type) && !type_has_bits(src_type)) {
ErrorMsg *msg = ir_add_error(ira, source_instr,
@ -20722,7 +20721,8 @@ static IrInstruction *ir_analyze_instruction_ptr_cast(IrAnalyze *ira, IrInstruct
if (type_is_invalid(src_type))
return ira->codegen->invalid_instruction;
return ir_analyze_ptr_cast(ira, &instruction->base, ptr, dest_type, dest_type_value);
return ir_analyze_ptr_cast(ira, &instruction->base, ptr, dest_type, dest_type_value,
instruction->safety_check_on);
}
static void buf_write_value_bytes_array(CodeGen *codegen, uint8_t *buf, ConstExprValue *val, size_t len) {

10
test/runtime_safety.zig
View File

@ -1,6 +1,16 @@
const tests = @import("tests.zig");
pub fn addCases(cases: *tests.CompareOutputContext) void {
cases.addRuntimeSafety("pointer casting null to non-optional pointer",
\\pub fn panic(message: []const u8, stack_trace: ?*@import("builtin").StackTrace) noreturn {
\\ @import("std").os.exit(126);
\\}
\\pub fn main() void {
\\ var c_ptr: [*c]u8 = 0;
\\ var zig_ptr: *u8 = c_ptr;
\\}
);
cases.addRuntimeSafety("@intToEnum - no matching tag value",
\\pub fn panic(message: []const u8, stack_trace: ?*@import("builtin").StackTrace) noreturn {
\\ @import("std").os.exit(126);