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Check that messages outside of the heap are not corrupted

Waiting messages for a process may be stored in a queue
outside of any heap or heap fragment belonging to the process.
This is an optimization added in a recent major release to
avoid garbage collection messages again and again if there
is a long message queue.

Until such message has been matched and accepted by
the remove_message/0 instruction, the message must not be
included in the root set for a garbage collection, as that
would corrupt the message. The loop_rec/2 instruction explicitly
turns off garbage collection of the process as long messages
are being matched.

However, if the compiler were to put references to a message
outside of the heap in an Y register (on the stack) and there
happened to be a GC when the process had been scheduled out,
the message would be corrupted and the runtime system would
crash sooner or later.

To ensure that doesn't happen, teach beam_validator to check
for references on the stack to messages outside of the heap.
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bjorng committed Apr 4, 2018
1 parent 1328163 commit 90853d8e7b50be13a3b71f4a1ed6b0407e1f7c2f
@@ -29,7 +29,7 @@
-include("beam_disasm.hrl").
-import(lists, [reverse/1,foldl/3,foreach/2,dropwhile/2]).
-import(lists, [any/2,dropwhile/2,foldl/3,foreach/2,reverse/1]).
%% To be called by the compiler.
@@ -365,7 +365,9 @@ valfun_1({recv_set,{f,Fail}}, Vst) when is_integer(Fail) ->
Vst;
%% Misc.
valfun_1(remove_message, Vst) ->
Vst;
%% The message term is no longer fragile. It can be used
%% without restrictions.
remove_fragility(Vst);
valfun_1({'%',_}, Vst) ->
Vst;
valfun_1({line,_}, Vst) ->
@@ -533,7 +535,7 @@ valfun_4({bif,element,{f,Fail},[Pos,Tuple],Dst}, Vst0) ->
Vst1 = branch_state(Fail, Vst0),
TupleType = upgrade_tuple_type({tuple,[get_tuple_size(PosType)]}, TupleType0),
Vst = set_type(TupleType, Tuple, Vst1),
set_type_reg(term, Dst, Vst);
set_type_reg(term, Tuple, Dst, Vst);
valfun_4({bif,raise,{f,0},Src,_Dst}, Vst) ->
validate_src(Src, Vst),
kill_state(Vst);
@@ -542,7 +544,8 @@ valfun_4(raw_raise=I, Vst) ->
valfun_4({bif,Op,{f,Fail},Src,Dst}, Vst0) ->
validate_src(Src, Vst0),
Vst = branch_state(Fail, Vst0),
Type = bif_type(Op, Src, Vst),
Type0 = bif_type(Op, Src, Vst),
Type = propagate_fragility(Type0, Src, Vst),
set_type_reg(Type, Dst, Vst);
valfun_4({gc_bif,Op,{f,Fail},Live,Src,Dst}, #vst{current=St0}=Vst0) ->
verify_live(Live, Vst0),
@@ -552,7 +555,8 @@ valfun_4({gc_bif,Op,{f,Fail},Live,Src,Dst}, #vst{current=St0}=Vst0) ->
Vst2 = branch_state(Fail, Vst1),
Vst = prune_x_regs(Live, Vst2),
validate_src(Src, Vst),
Type = bif_type(Op, Src, Vst),
Type0 = bif_type(Op, Src, Vst),
Type = propagate_fragility(Type0, Src, Vst),
set_type_reg(Type, Dst, Vst);
valfun_4(return, #vst{current=#st{numy=none}}=Vst) ->
assert_term({x,0}, Vst),
@@ -563,13 +567,20 @@ valfun_4({jump,{f,Lbl}}, Vst) ->
kill_state(branch_state(Lbl, Vst));
valfun_4({loop_rec,{f,Fail},Dst}, Vst0) ->
Vst = branch_state(Fail, Vst0),
set_type_reg(term, Dst, Vst);
%% This term may not be part of the root set until
%% remove_message/0 is executed. If control transfers
%% to the loop_rec_end/1 instruction, no part of this
%% this term must be stored in a Y register.
set_type_reg({fragile,term}, Dst, Vst);
valfun_4({wait,_}, Vst) ->
verify_y_init(Vst),
kill_state(Vst);
valfun_4({wait_timeout,_,Src}, Vst) ->
assert_term(Src, Vst),
verify_y_init(Vst),
Vst;
valfun_4({loop_rec_end,_}, Vst) ->
verify_y_init(Vst),
kill_state(Vst);
valfun_4(timeout, #vst{current=St}=Vst) ->
Vst#vst{current=St#st{x=init_regs(0, term)}};
@@ -589,17 +600,17 @@ valfun_4({select_tuple_arity,Tuple,{f,Fail},{list,Choices}}, Vst) ->
kill_state(branch_arities(Choices, Tuple, branch_state(Fail, Vst)));
valfun_4({get_list,Src,D1,D2}, Vst0) ->
assert_type(cons, Src, Vst0),
Vst = set_type_reg(term, D1, Vst0),
set_type_reg(term, D2, Vst);
Vst = set_type_reg(term, Src, D1, Vst0),
set_type_reg(term, Src, D2, Vst);
valfun_4({get_hd,Src,Dst}, Vst) ->
assert_type(cons, Src, Vst),
set_type_reg(term, Dst, Vst);
set_type_reg(term, Src, Dst, Vst);
valfun_4({get_tl,Src,Dst}, Vst) ->
assert_type(cons, Src, Vst),
set_type_reg(term, Dst, Vst);
set_type_reg(term, Src, Dst, Vst);
valfun_4({get_tuple_element,Src,I,Dst}, Vst) ->
assert_type({tuple_element,I+1}, Src, Vst),
set_type_reg(term, Dst, Vst);
set_type_reg(term, Src, Dst, Vst);
%% New bit syntax matching instructions.
valfun_4({test,bs_start_match2,{f,Fail},Live,[Ctx,NeedSlots],Ctx}, Vst0) ->
@@ -625,7 +636,7 @@ valfun_4({test,bs_start_match2,{f,Fail},Live,[Src,Slots],Dst}, Vst0) ->
verify_live(Live, Vst0),
Vst1 = prune_x_regs(Live, Vst0),
Vst = branch_state(Fail, Vst1),
set_type_reg(bsm_match_state(Slots), Dst, Vst);
set_type_reg(bsm_match_state(Slots), Src, Dst, Vst);
valfun_4({test,bs_match_string,{f,Fail},[Ctx,_,_]}, Vst) ->
bsm_validate_context(Ctx, Vst),
branch_state(Fail, Vst);
@@ -650,7 +661,8 @@ valfun_4({test,bs_get_integer2,{f,Fail},Live,[Ctx,_,_,_],Dst}, Vst) ->
valfun_4({test,bs_get_float2,{f,Fail},Live,[Ctx,_,_,_],Dst}, Vst) ->
validate_bs_get(Fail, Ctx, Live, {float, []}, Dst, Vst);
valfun_4({test,bs_get_binary2,{f,Fail},Live,[Ctx,_,_,_],Dst}, Vst) ->
validate_bs_get(Fail, Ctx, Live, term, Dst, Vst);
Type = propagate_fragility(term, [Ctx], Vst),
validate_bs_get(Fail, Ctx, Live, Type, Dst, Vst);
valfun_4({test,bs_get_utf8,{f,Fail},Live,[Ctx,_],Dst}, Vst) ->
validate_bs_get(Fail, Ctx, Live, {integer, []}, Dst, Vst);
valfun_4({test,bs_get_utf16,{f,Fail},Live,[Ctx,_],Dst}, Vst) ->
@@ -790,7 +802,7 @@ verify_get_map(Fail, Src, List, Vst0) ->
Vst2 = branch_state(Fail, Vst1),
Keys = extract_map_keys(List),
assert_unique_map_keys(Keys),
verify_get_map_pair(List,Vst0,Vst2).
verify_get_map_pair(List, Src, Vst0, Vst2).
extract_map_vals([_Key,Val|T]) ->
[Val|extract_map_vals(T)];
@@ -800,10 +812,11 @@ extract_map_keys([Key,_Val|T]) ->
[Key|extract_map_keys(T)];
extract_map_keys([]) -> [].
verify_get_map_pair([],_,Vst) -> Vst;
verify_get_map_pair([Src,Dst|Vs],Vst0,Vsti) ->
verify_get_map_pair([Src,Dst|Vs], Map, Vst0, Vsti0) ->
assert_term(Src, Vst0),
verify_get_map_pair(Vs,Vst0,set_type_reg(term,Dst,Vsti)).
Vsti = set_type_reg(term, Map, Dst, Vsti0),
verify_get_map_pair(Vs, Map, Vst0, Vsti);
verify_get_map_pair([], _Map, _Vst0, Vst) -> Vst.
verify_put_map(Fail, Src, Dst, Live, List, Vst0) ->
assert_type(map, Src, Vst0),
@@ -1093,10 +1106,11 @@ bsm_validate_context(Reg, Vst) ->
bsm_get_context({x,X}=Reg, #vst{current=#st{x=Xs}}=_Vst) when is_integer(X) ->
case gb_trees:lookup(X, Xs) of
{value,#ms{}=Ctx} -> Ctx;
{value,{fragile,#ms{}=Ctx}} -> Ctx;
_ -> error({no_bsm_context,Reg})
end;
bsm_get_context(Reg, _) -> error({bad_source,Reg}).
bsm_save(Reg, {atom,start}, Vst) ->
%% Save point refering to where the match started.
%% It is always valid. But don't forget to validate the context register.
@@ -1133,13 +1147,34 @@ set_type(Type, {x,_}=Reg, Vst) -> set_type_reg(Type, Reg, Vst);
set_type(Type, {y,_}=Reg, Vst) -> set_type_y(Type, Reg, Vst);
set_type(_, _, #vst{}=Vst) -> Vst.
set_type_reg(Type, {x,X}=Reg, #vst{current=#st{x=Xs}=St}=Vst)
when is_integer(X), 0 =< X ->
check_limit(Reg),
Vst#vst{current=St#st{x=gb_trees:enter(X, Type, Xs)}};
set_type_reg(Type, Src, Dst, Vst) ->
case get_term_type_1(Src, Vst) of
{fragile,_} ->
set_type_reg(make_fragile(Type), Dst, Vst);
_ ->
set_type_reg(Type, Dst, Vst)
end.
set_type_reg(Type, {x,_}=Reg, Vst) ->
set_type_x(Type, Reg, Vst);
set_type_reg(Type, Reg, Vst) ->
set_type_y(Type, Reg, Vst).
set_type_x(Type, {x,X}=Reg, #vst{current=#st{x=Xs0}=St}=Vst)
when is_integer(X), 0 =< X ->
check_limit(Reg),
Xs = case gb_trees:lookup(X, Xs0) of
none ->
gb_trees:insert(X, Type, Xs0);
{value,{fragile,_}} ->
gb_trees:update(X, make_fragile(Type), Xs0);
{value,_} ->
gb_trees:update(X, Type, Xs0)
end,
Vst#vst{current=St#st{x=Xs}};
set_type_x(Type, Reg, #vst{}) ->
error({invalid_store,Reg,Type}).
set_type_y(Type, {y,Y}=Reg, #vst{current=#st{y=Ys0}=St}=Vst)
when is_integer(Y), 0 =< Y ->
check_limit(Reg),
@@ -1157,6 +1192,9 @@ set_type_y(Type, {y,Y}=Reg, #vst{current=#st{y=Ys0}=St}=Vst)
Vst#vst{current=St#st{y=Ys}};
set_type_y(Type, Reg, #vst{}) -> error({invalid_store,Reg,Type}).
make_fragile({fragile,_}=Type) -> Type;
make_fragile(Type) -> {fragile,Type}.
set_catch_end({y,Y}, #vst{current=#st{y=Ys0}=St}=Vst) ->
Ys = gb_trees:update(Y, initialized, Ys0),
Vst#vst{current=St#st{y=Ys}}.
@@ -1257,9 +1295,26 @@ assert_term(Src, Vst) ->
%%
%% map Map.
%%
%%
%%
%% FRAGILITY
%% ---------
%%
%% The loop_rec/2 instruction may return a reference to a term that is
%% not part of the root set. That term or any part of it must not be
%% included in a garbage collection. Therefore, the term (or any part
%% of it) must not be stored in an Y register.
%%
%% Such terms are wrapped in a {fragile,Type} tuple, where Type is one
%% of the types described above.
assert_type(WantedType, Term, Vst) ->
assert_type(WantedType, get_term_type(Term, Vst)).
case get_term_type(Term, Vst) of
{fragile,Type} ->
assert_type(WantedType, Type);
Type ->
assert_type(WantedType, Type)
end.
assert_type(Correct, Correct) -> ok;
assert_type(float, {float,_}) -> ok;
@@ -1285,14 +1340,19 @@ assert_type(Needed, Actual) ->
%% is inconsistent, and we know that some instructions will never
%% be executed at run-time.
upgrade_tuple_type({tuple,[Sz]}, {tuple,[OldSz]}=T) when Sz < OldSz ->
upgrade_tuple_type(NewType, {fragile,OldType}) ->
make_fragile(upgrade_tuple_type_1(NewType, OldType));
upgrade_tuple_type(NewType, OldType) ->
upgrade_tuple_type_1(NewType, OldType).
upgrade_tuple_type_1({tuple,[Sz]}, {tuple,[OldSz]}=T) when Sz < OldSz ->
%% The old type has a higher value for the least tuple size.
T;
upgrade_tuple_type({tuple,[Sz]}, {tuple,OldSz}=T)
upgrade_tuple_type_1({tuple,[Sz]}, {tuple,OldSz}=T)
when is_integer(Sz), is_integer(OldSz), Sz =< OldSz ->
%% The old size is exact, and the new size is smaller than the old size.
T;
upgrade_tuple_type({tuple,_}=T, _) ->
upgrade_tuple_type_1({tuple,_}=T, _) ->
%% The new type information is exact or has a higher value for
%% the least tuple size.
%% Note that inconsistencies are also handled in this
@@ -1459,6 +1519,14 @@ merge_y_regs_1(_, _, Regs) -> Regs.
%% merge_types(Type1, Type2) -> Type
%% Return the most specific type possible.
%% Note: Type1 must NOT be the same as Type2.
merge_types({fragile,Same}=Type, Same) ->
Type;
merge_types({fragile,T1}, T2) ->
make_fragile(merge_types(T1, T2));
merge_types(Same, {fragile,Same}=Type) ->
Type;
merge_types(T1, {fragile,T2}) ->
make_fragile(merge_types(T1, T2));
merge_types(uninitialized=I, _) -> I;
merge_types(_, uninitialized=I) -> I;
merge_types(initialized=I, _) -> I;
@@ -1509,6 +1577,10 @@ verify_y_init(#vst{current=#st{y=Ys}}) ->
verify_y_init_1([]) -> ok;
verify_y_init_1([{Y,uninitialized}|_]) ->
error({uninitialized_reg,{y,Y}});
verify_y_init_1([{Y,{fragile,_}}|_]) ->
%% Unsafe. This term may be outside any heap belonging
%% to the process and would be corrupted by a GC.
error({fragile_message_reference,{y,Y}});
verify_y_init_1([{_,_}|Ys]) ->
verify_y_init_1(Ys).
@@ -1554,6 +1626,27 @@ eat_heap_float(#vst{current=#st{hf=HeapFloats0}=St}=Vst) ->
Vst#vst{current=St#st{hf=HeapFloats}}
end.
remove_fragility(#vst{current=#st{x=Xs0,y=Ys0}=St0}=Vst) ->
F = fun(_, {fragile,Type}) -> Type;
(_, Type) -> Type
end,
Xs = gb_trees:map(F, Xs0),
Ys = gb_trees:map(F, Ys0),
St = St0#st{x=Xs,y=Ys},
Vst#vst{current=St}.
propagate_fragility(Type, Ss, Vst) ->
F = fun(S) ->
case get_term_type_1(S, Vst) of
{fragile,_} -> true;
_ -> false
end
end,
case any(F, Ss) of
true -> make_fragile(Type);
false -> Type
end.
bif_type('-', Src, Vst) ->
arith_type(Src, Vst);
bif_type('+', Src, Vst) ->
@@ -33,7 +33,8 @@
state_after_fault_in_catch/1,no_exception_in_catch/1,
undef_label/1,illegal_instruction/1,failing_gc_guard_bif/1,
map_field_lists/1,cover_bin_opt/1,
val_dsetel/1,bad_tuples/1,bad_try_catch_nesting/1]).
val_dsetel/1,bad_tuples/1,bad_try_catch_nesting/1,
receive_stacked/1]).
-include_lib("common_test/include/ct.hrl").
@@ -62,7 +63,8 @@ groups() ->
state_after_fault_in_catch,no_exception_in_catch,
undef_label,illegal_instruction,failing_gc_guard_bif,
map_field_lists,cover_bin_opt,val_dsetel,
bad_tuples,bad_try_catch_nesting]}].
bad_tuples,bad_try_catch_nesting,
receive_stacked]}].
init_per_suite(Config) ->
Config.
@@ -531,6 +533,52 @@ bad_try_catch_nesting(Config) ->
{bad_try_catch_nesting,{y,2},[{{y,1},{trytag,[5]}}]}}}] = Errors,
ok.
receive_stacked(Config) ->
Mod = ?FUNCTION_NAME,
Errors = do_val(Mod, Config),
[{{receive_stacked,f1,0},
{{loop_rec_end,{f,3}},
17,
{fragile_message_reference,{y,0}}}},
{{receive_stacked,f2,0},
{{test_heap,3,0},10,{fragile_message_reference,{y,1}}}},
{{receive_stacked,f3,0},
{{test_heap,3,0},10,{fragile_message_reference,{y,1}}}},
{{receive_stacked,f4,0},
{{test_heap,3,0},10,{fragile_message_reference,{y,1}}}},
{{receive_stacked,f5,0},
{{loop_rec_end,{f,23}},
23,
{fragile_message_reference,{y,1}}}},
{{receive_stacked,f6,0},
{{gc_bif,byte_size,{f,29},0,[{y,0}],{x,0}},
12,
{fragile_message_reference,{y,0}}}},
{{receive_stacked,f7,0},
{{loop_rec_end,{f,33}},
20,
{fragile_message_reference,{y,0}}}},
{{receive_stacked,f8,0},
{{loop_rec_end,{f,38}},
20,
{fragile_message_reference,{y,0}}}},
{{receive_stacked,m1,0},
{{loop_rec_end,{f,43}},
19,
{fragile_message_reference,{y,0}}}},
{{receive_stacked,m2,0},
{{loop_rec_end,{f,48}},
33,
{fragile_message_reference,{y,0}}}}] = Errors,
%% Compile the original source code as a smoke test.
Data = proplists:get_value(data_dir, Config),
Base = atom_to_list(Mod),
File = filename:join(Data, Base),
{ok,Mod,_} = compile:file(File, [binary]),
ok.
%%%-------------------------------------------------------------------------
transform_remove(Remove, Module) ->
Oops, something went wrong.

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