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[Ada] Buffer reading overflow in dispatch table initialization
- From: Pierre-Marie de Rodat <derodat at adacore dot com>
- To: gcc-patches at gcc dot gnu dot org
- Cc: Javier Miranda <miranda at adacore dot com>
- Date: Mon, 19 Aug 2019 04:39:01 -0400
- Subject: [Ada] Buffer reading overflow in dispatch table initialization
For tagged types not defined at library level that derive from library
level tagged types the compiler may generate code to initialize their
dispatch table of predefined primitives copying from the parent type
data stored in memory after the dispatch table of the parent; that is,
at runtime the initialization of dispatch tables overflows reading the
parent dispatch table.
This problem does not affect the execution of the program since the
target dispatch table always has enough space to store the extra data,
and after such copy the compiler generates code to complete the
initialization of the dispatch table.
The following test must compile and execute without errors.
package pkg_a is
type Root is tagged null record;
end pkg_a;
with pkg_a;
procedure main is
type Derived is new pkg_a.Root with null record; -- Test
begin
null;
end main;
Command: gnatmake -q main -fsanitize=address; ./main
Tested on x86_64-pc-linux-gnu, committed on trunk
2019-08-19 Javier Miranda <miranda@adacore.com>
gcc/ada/
PR ada/65696
* exp_atag.ads, exp_atag.adb (Build_Inherit_Predefined_Prims):
Adding formal to specify how many predefined primitives are
inherited from the parent type.
* exp_disp.adb (Number_Of_Predefined_Prims): New subprogram.
(Make_Secondary_DT): Compute the number of predefined primitives
of all tagged types (including tagged types not defined at
library level). Previously we unconditionally relied on the
Max_Predef_Prims constant value when building the dispatch
tables of tagged types not defined at library level (thus
consuming more memory for their dispatch tables than required).
(Make_DT): Compute the number of predefined primitives that must
be inherited from their parent type when building the dispatch
tables of tagged types not defined at library level. Previously
we unconditionally relied on the Max_Predef_Prims constant value
when building the dispatch tables of tagged types not defined at
library level (thus copying more data than required from the
parent type).
--- gcc/ada/exp_atag.adb
+++ gcc/ada/exp_atag.adb
@@ -742,9 +742,10 @@ package body Exp_Atag is
------------------------------------
function Build_Inherit_Predefined_Prims
- (Loc : Source_Ptr;
- Old_Tag_Node : Node_Id;
- New_Tag_Node : Node_Id) return Node_Id
+ (Loc : Source_Ptr;
+ Old_Tag_Node : Node_Id;
+ New_Tag_Node : Node_Id;
+ Num_Predef_Prims : Int) return Node_Id
is
begin
return
@@ -759,7 +760,7 @@ package body Exp_Atag is
New_Tag_Node)))),
Discrete_Range => Make_Range (Loc,
Make_Integer_Literal (Loc, Uint_1),
- New_Occurrence_Of (RTE (RE_Max_Predef_Prims), Loc))),
+ Make_Integer_Literal (Loc, Num_Predef_Prims))),
Expression =>
Make_Slice (Loc,
@@ -772,7 +773,7 @@ package body Exp_Atag is
Discrete_Range =>
Make_Range (Loc,
Make_Integer_Literal (Loc, 1),
- New_Occurrence_Of (RTE (RE_Max_Predef_Prims), Loc))));
+ Make_Integer_Literal (Loc, Num_Predef_Prims))));
end Build_Inherit_Predefined_Prims;
-------------------------
--- gcc/ada/exp_atag.ads
+++ gcc/ada/exp_atag.ads
@@ -109,9 +109,10 @@ package Exp_Atag is
-- generated code handles primary and secondary dispatch tables of Typ.
function Build_Inherit_Predefined_Prims
- (Loc : Source_Ptr;
- Old_Tag_Node : Node_Id;
- New_Tag_Node : Node_Id) return Node_Id;
+ (Loc : Source_Ptr;
+ Old_Tag_Node : Node_Id;
+ New_Tag_Node : Node_Id;
+ Num_Predef_Prims : Int) return Node_Id;
-- Build code that inherits the predefined primitives of the parent.
--
-- Generates: Predefined_DT (New_T).D (All_Predefined_Prims) :=
--- gcc/ada/exp_disp.adb
+++ gcc/ada/exp_disp.adb
@@ -3817,6 +3817,9 @@ package body Exp_Disp is
-- this secondary dispatch table by Make_Tags when its unique external
-- name was generated.
+ function Number_Of_Predefined_Prims (Typ : Entity_Id) return Nat;
+ -- Returns the number of predefined primitives of Typ
+
------------------------------
-- Check_Premature_Freezing --
------------------------------
@@ -3970,12 +3973,10 @@ package body Exp_Disp is
DT_Constr_List : List_Id;
DT_Aggr_List : List_Id;
Empty_DT : Boolean := False;
- Nb_Predef_Prims : Nat := 0;
Nb_Prim : Nat;
New_Node : Node_Id;
OSD : Entity_Id;
OSD_Aggr_List : List_Id;
- Pos : Nat;
Prim : Entity_Id;
Prim_Elmt : Elmt_Id;
Prim_Ops_Aggr_List : List_Id;
@@ -4022,38 +4023,12 @@ package body Exp_Disp is
-- predef-prim-op-thunk-n'address);
-- for Predef_Prims'Alignment use Address'Alignment
- -- Stage 1: Calculate the number of predefined primitives
-
- if not Building_Static_DT (Typ) then
- Nb_Predef_Prims := Max_Predef_Prims;
- else
- Prim_Elmt := First_Elmt (Primitive_Operations (Typ));
- while Present (Prim_Elmt) loop
- Prim := Node (Prim_Elmt);
-
- if Is_Predefined_Dispatching_Operation (Prim)
- and then not Is_Abstract_Subprogram (Prim)
- then
- Pos := UI_To_Int (DT_Position (Prim));
-
- if Pos > Nb_Predef_Prims then
- Nb_Predef_Prims := Pos;
- end if;
- end if;
-
- Next_Elmt (Prim_Elmt);
- end loop;
- end if;
-
- if Generate_SCIL then
- Nb_Predef_Prims := 0;
- end if;
-
- -- Stage 2: Create the thunks associated with the predefined
- -- primitives and save their entity to fill the aggregate.
+ -- Create the thunks associated with the predefined primitives and
+ -- save their entity to fill the aggregate.
declare
- Prim_Table : array (Nat range 1 .. Nb_Predef_Prims) of Entity_Id;
+ Nb_P_Prims : constant Nat := Number_Of_Predefined_Prims (Typ);
+ Prim_Table : array (Nat range 1 .. Nb_P_Prims) of Entity_Id;
Decl : Node_Id;
Thunk_Id : Entity_Id;
Thunk_Code : Node_Id;
@@ -4525,6 +4500,44 @@ package body Exp_Disp is
Append_Elmt (Iface_DT, DT_Decl);
end Make_Secondary_DT;
+ --------------------------------
+ -- Number_Of_Predefined_Prims --
+ --------------------------------
+
+ function Number_Of_Predefined_Prims (Typ : Entity_Id) return Nat is
+ Nb_Predef_Prims : Nat := 0;
+
+ begin
+ if not Generate_SCIL then
+ declare
+ Prim : Entity_Id;
+ Prim_Elmt : Elmt_Id;
+ Pos : Nat;
+
+ begin
+ Prim_Elmt := First_Elmt (Primitive_Operations (Typ));
+ while Present (Prim_Elmt) loop
+ Prim := Node (Prim_Elmt);
+
+ if Is_Predefined_Dispatching_Operation (Prim)
+ and then not Is_Abstract_Subprogram (Prim)
+ then
+ Pos := UI_To_Int (DT_Position (Prim));
+
+ if Pos > Nb_Predef_Prims then
+ Nb_Predef_Prims := Pos;
+ end if;
+ end if;
+
+ Next_Elmt (Prim_Elmt);
+ end loop;
+ end;
+ end if;
+
+ pragma Assert (Nb_Predef_Prims <= Max_Predef_Prims);
+ return Nb_Predef_Prims;
+ end Number_Of_Predefined_Prims;
+
-- Local variables
Elab_Code : constant List_Id := New_List;
@@ -4584,7 +4597,6 @@ package body Exp_Disp is
I_Depth : Nat := 0;
Iface_Table_Node : Node_Id;
Name_ITable : Name_Id;
- Nb_Predef_Prims : Nat := 0;
Nb_Prim : Nat := 0;
New_Node : Node_Id;
Num_Ifaces : Nat := 0;
@@ -5924,112 +5936,85 @@ package body Exp_Disp is
else
declare
- Pos : Nat;
+ Nb_P_Prims : constant Nat := Number_Of_Predefined_Prims (Typ);
+ Prim_Table : array (Nat range 1 .. Nb_P_Prims) of Entity_Id;
+ Decl : Node_Id;
+ E : Entity_Id;
begin
- if not Building_Static_DT (Typ) then
- Nb_Predef_Prims := Max_Predef_Prims;
+ Prim_Ops_Aggr_List := New_List;
+ Prim_Table := (others => Empty);
- else
- Prim_Elmt := First_Elmt (Primitive_Operations (Typ));
+ if Building_Static_DT (Typ) then
+ Prim_Elmt := First_Elmt (Primitive_Operations (Typ));
while Present (Prim_Elmt) loop
Prim := Node (Prim_Elmt);
if Is_Predefined_Dispatching_Operation (Prim)
and then not Is_Abstract_Subprogram (Prim)
+ and then not Is_Eliminated (Prim)
+ and then not Generate_SCIL
+ and then not Present (Prim_Table
+ (UI_To_Int (DT_Position (Prim))))
then
- Pos := UI_To_Int (DT_Position (Prim));
-
- if Pos > Nb_Predef_Prims then
- Nb_Predef_Prims := Pos;
- end if;
+ E := Ultimate_Alias (Prim);
+ pragma Assert (not Is_Abstract_Subprogram (E));
+ Prim_Table (UI_To_Int (DT_Position (Prim))) := E;
end if;
Next_Elmt (Prim_Elmt);
end loop;
end if;
- declare
- Prim_Table : array
- (Nat range 1 .. Nb_Predef_Prims) of Entity_Id;
- Decl : Node_Id;
- E : Entity_Id;
-
- begin
- Prim_Ops_Aggr_List := New_List;
-
- Prim_Table := (others => Empty);
-
- if Building_Static_DT (Typ) then
- Prim_Elmt := First_Elmt (Primitive_Operations (Typ));
- while Present (Prim_Elmt) loop
- Prim := Node (Prim_Elmt);
-
- if Is_Predefined_Dispatching_Operation (Prim)
- and then not Is_Abstract_Subprogram (Prim)
- and then not Is_Eliminated (Prim)
- and then not Present (Prim_Table
- (UI_To_Int (DT_Position (Prim))))
- then
- E := Ultimate_Alias (Prim);
- pragma Assert (not Is_Abstract_Subprogram (E));
- Prim_Table (UI_To_Int (DT_Position (Prim))) := E;
- end if;
-
- Next_Elmt (Prim_Elmt);
- end loop;
+ for J in Prim_Table'Range loop
+ if Present (Prim_Table (J)) then
+ New_Node :=
+ Unchecked_Convert_To (RTE (RE_Prim_Ptr),
+ Make_Attribute_Reference (Loc,
+ Prefix =>
+ New_Occurrence_Of (Prim_Table (J), Loc),
+ Attribute_Name => Name_Unrestricted_Access));
+ else
+ New_Node := Make_Null (Loc);
end if;
- for J in Prim_Table'Range loop
- if Present (Prim_Table (J)) then
- New_Node :=
- Unchecked_Convert_To (RTE (RE_Prim_Ptr),
- Make_Attribute_Reference (Loc,
- Prefix =>
- New_Occurrence_Of (Prim_Table (J), Loc),
- Attribute_Name => Name_Unrestricted_Access));
- else
- New_Node := Make_Null (Loc);
- end if;
-
- Append_To (Prim_Ops_Aggr_List, New_Node);
- end loop;
+ Append_To (Prim_Ops_Aggr_List, New_Node);
+ end loop;
- New_Node :=
- Make_Aggregate (Loc,
- Expressions => Prim_Ops_Aggr_List);
+ New_Node :=
+ Make_Aggregate (Loc,
+ Expressions => Prim_Ops_Aggr_List);
- Decl :=
- Make_Subtype_Declaration (Loc,
- Defining_Identifier => Make_Temporary (Loc, 'S'),
- Subtype_Indication =>
- New_Occurrence_Of (RTE (RE_Address_Array), Loc));
+ Decl :=
+ Make_Subtype_Declaration (Loc,
+ Defining_Identifier => Make_Temporary (Loc, 'S'),
+ Subtype_Indication =>
+ New_Occurrence_Of (RTE (RE_Address_Array), Loc));
- Append_To (Result, Decl);
+ Append_To (Result, Decl);
- Append_To (Result,
- Make_Object_Declaration (Loc,
- Defining_Identifier => Predef_Prims,
- Aliased_Present => True,
- Constant_Present => Building_Static_DT (Typ),
- Object_Definition =>
- New_Occurrence_Of (Defining_Identifier (Decl), Loc),
- Expression => New_Node));
+ Append_To (Result,
+ Make_Object_Declaration (Loc,
+ Defining_Identifier => Predef_Prims,
+ Aliased_Present => True,
+ Constant_Present => Building_Static_DT (Typ),
+ Object_Definition =>
+ New_Occurrence_Of (Defining_Identifier (Decl), Loc),
+ Expression => New_Node));
- -- Remember aggregates initializing dispatch tables
+ -- Remember aggregates initializing dispatch tables
- Append_Elmt (New_Node, DT_Aggr);
+ Append_Elmt (New_Node, DT_Aggr);
- Append_To (Result,
- Make_Attribute_Definition_Clause (Loc,
- Name => New_Occurrence_Of (Predef_Prims, Loc),
- Chars => Name_Alignment,
- Expression =>
- Make_Attribute_Reference (Loc,
- Prefix =>
- New_Occurrence_Of (RTE (RE_Integer_Address), Loc),
- Attribute_Name => Name_Alignment)));
- end;
+ Append_To (Result,
+ Make_Attribute_Definition_Clause (Loc,
+ Name => New_Occurrence_Of (Predef_Prims, Loc),
+ Chars => Name_Alignment,
+ Expression =>
+ Make_Attribute_Reference (Loc,
+ Prefix =>
+ New_Occurrence_Of (RTE (RE_Integer_Address), Loc),
+ Attribute_Name => Name_Alignment)));
end;
-- Stage 1: Initialize the discriminant and the record components
@@ -6301,7 +6286,9 @@ package body Exp_Disp is
(Node
(Next_Elmt
(First_Elmt
- (Access_Disp_Table (Typ)))), Loc)));
+ (Access_Disp_Table (Typ)))), Loc),
+ Num_Predef_Prims =>
+ Number_Of_Predefined_Prims (Parent_Typ)));
if Nb_Prims /= 0 then
Append_To (Elab_Code,
@@ -6390,7 +6377,10 @@ package body Exp_Disp is
Unchecked_Convert_To (RTE (RE_Tag),
New_Occurrence_Of
(Node (Next_Elmt (Sec_DT_Typ)),
- Loc))));
+ Loc)),
+ Num_Predef_Prims =>
+ Number_Of_Predefined_Prims
+ (Parent_Typ)));
if Num_Prims /= 0 then
Append_To (Elab_Code,
@@ -6436,7 +6426,10 @@ package body Exp_Disp is
Unchecked_Convert_To (RTE (RE_Tag),
New_Occurrence_Of
(Node (Next_Elmt (Sec_DT_Typ)),
- Loc))));
+ Loc)),
+ Num_Predef_Prims =>
+ Number_Of_Predefined_Prims
+ (Parent_Typ)));
if Num_Prims /= 0 then
Append_To (Elab_Code,