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authorMikael Pettersson <[email protected]>2015-02-04 20:27:37 +0100
committerMikael Pettersson <[email protected]>2015-02-04 20:27:37 +0100
commit7e147a05683c709128b6777d0c360fcde067f567 (patch)
tree370b8fd2856d4e4b1fd88697ea4e7bee0658b59a /erts/emulator/test/big_SUITE.erl
parent42d6afe554e11813385dbf175fce58f995c2f9e5 (diff)
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don't create oversize bignums in binary matching
Bignums are artifically restricted in size. Arithmetic and logical operations check the sizes of resulting bignums, and turn oversize results into system_limit exceptions. However, this check is not performed when bignums are constructed by binary matching. The consequence is that such matchings can construct oversize bignums that satisfy is_integer/1 yet don't work. Performing arithmetic such as Term - 0 fails with a system_limit exception. Worse, performing a logical operation such as Term band Term results in []. The latter occurs because the size checking (e.g. in erts_band()) is a simple ASSERT(is_not_nil(...)) on the result of the bignum operation, which internally is [] (NIL) in the case of oversize results. However, ASSERT is a no-op in release builds, so the error goes unnoticed and [] is returned as the result of the band/2. This patch addresses this by preventing oversize bignums from entering the VM via binary matching: - the internal bytes_to_big() procedure is augmented to return NIL for oversize results, just like big_norm() - callers of bytes_to_big() are augmented to check for NIL returns and signal errors in those cases - erts_bs_get_integer_2() can only fail with badmatch, so that is the Erlang-level result of oversize bignums from binary matches - big_SUITE.erl is extended with a test case that fails without this fix (no error signalled) and passes with it (badmatch occurs) Credit goes to Nico Kruber for the initial bug report.
Diffstat (limited to 'erts/emulator/test/big_SUITE.erl')
-rw-r--r--erts/emulator/test/big_SUITE.erl14
1 files changed, 12 insertions, 2 deletions
diff --git a/erts/emulator/test/big_SUITE.erl b/erts/emulator/test/big_SUITE.erl
index 413bd3bcae..3193d56e2a 100644
--- a/erts/emulator/test/big_SUITE.erl
+++ b/erts/emulator/test/big_SUITE.erl
@@ -23,7 +23,7 @@
init_per_group/2,end_per_group/2]).
-export([t_div/1, eq_28/1, eq_32/1, eq_big/1, eq_math/1, big_literals/1,
borders/1, negative/1, big_float_1/1, big_float_2/1,
- shift_limit_1/1, powmod/1, system_limit/1, otp_6692/1]).
+ shift_limit_1/1, powmod/1, system_limit/1, toobig/1, otp_6692/1]).
%% Internal exports.
-export([eval/1]).
@@ -40,7 +40,7 @@ suite() -> [{ct_hooks,[ts_install_cth]}].
all() ->
[t_div, eq_28, eq_32, eq_big, eq_math, big_literals,
borders, negative, {group, big_float}, shift_limit_1,
- powmod, system_limit, otp_6692].
+ powmod, system_limit, toobig, otp_6692].
groups() ->
[{big_float, [], [big_float_1, big_float_2]}].
@@ -370,6 +370,16 @@ maxbig() ->
id(I) -> I.
+toobig(Config) when is_list(Config) ->
+ ?line {'EXIT',{{badmatch,_},_}} = (catch toobig()),
+ ok.
+
+toobig() ->
+ A = erlang:term_to_binary(lists:seq(1000000, 2200000)),
+ ASize = erlang:bit_size(A),
+ <<ANr:ASize>> = A, % should fail
+ ANr band ANr.
+
otp_6692(suite) ->
[];
otp_6692(doc) ->