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authorJohn Högberg <[email protected]>2017-07-26 16:09:55 +0200
committerJohn Högberg <[email protected]>2017-08-01 11:23:01 +0200
commit0322232e3603ae098177e7fe5fcf81f2ed58ea00 (patch)
treeed73c1f48d1e811bfa6aea190f890b1f18d83693 /erts/emulator
parent74a95b3d511177a9b35c2b0272b9ca5511b6f750 (diff)
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Check for overflow when appending binaries, and error out with system_limit
This fixes the following bug: A = <<0:((1 bsl 32)-8)>>, B = <<2, 3>>. B =:= <<A/binary,1,B/binary>>. %% Evaluated to true...
Diffstat (limited to 'erts/emulator')
-rw-r--r--erts/emulator/beam/erl_bits.c31
-rw-r--r--erts/emulator/test/bs_construct_SUITE.erl28
2 files changed, 55 insertions, 4 deletions
diff --git a/erts/emulator/beam/erl_bits.c b/erts/emulator/beam/erl_bits.c
index 01734c55d7..c9e09501ff 100644
--- a/erts/emulator/beam/erl_bits.c
+++ b/erts/emulator/beam/erl_bits.c
@@ -1324,7 +1324,14 @@ erts_bs_append(Process* c_p, Eterm* reg, Uint live, Eterm build_size_term,
goto badarg;
}
}
+
+ if((ERTS_UINT_MAX - build_size_in_bits) < erts_bin_offset) {
+ c_p->freason = SYSTEM_LIMIT;
+ return THE_NON_VALUE;
+ }
+
used_size_in_bits = erts_bin_offset + build_size_in_bits;
+
sb->is_writable = 0; /* Make sure that no one else can write. */
pb->size = NBYTES(used_size_in_bits);
pb->flags |= PB_ACTIVE_WRITER;
@@ -1398,9 +1405,21 @@ erts_bs_append(Process* c_p, Eterm* reg, Uint live, Eterm build_size_term,
goto badarg;
}
}
- used_size_in_bits = erts_bin_offset + build_size_in_bits;
- used_size_in_bytes = NBYTES(used_size_in_bits);
- bin_size = 2*used_size_in_bytes;
+
+ if((ERTS_UINT_MAX - build_size_in_bits) < erts_bin_offset) {
+ c_p->freason = SYSTEM_LIMIT;
+ return THE_NON_VALUE;
+ }
+
+ used_size_in_bits = erts_bin_offset + build_size_in_bits;
+ used_size_in_bytes = NBYTES(used_size_in_bits);
+
+ if(used_size_in_bits < (ERTS_UINT_MAX / 2)) {
+ bin_size = 2 * used_size_in_bytes;
+ } else {
+ bin_size = NBYTES(ERTS_UINT_MAX);
+ }
+
bin_size = (bin_size < 256) ? 256 : bin_size;
/*
@@ -1491,6 +1510,12 @@ erts_bs_private_append(Process* p, Eterm bin, Eterm build_size_term, Uint unit)
* Calculate new size in bytes.
*/
erts_bin_offset = 8*sb->size + sb->bitsize;
+
+ if((ERTS_UINT_MAX - build_size_in_bits) < erts_bin_offset) {
+ p->freason = SYSTEM_LIMIT;
+ return THE_NON_VALUE;
+ }
+
pos_in_bits_after_build = erts_bin_offset + build_size_in_bits;
pb->size = (pos_in_bits_after_build+7) >> 3;
pb->flags |= PB_ACTIVE_WRITER;
diff --git a/erts/emulator/test/bs_construct_SUITE.erl b/erts/emulator/test/bs_construct_SUITE.erl
index cadb30e1a4..06f3bc2ff8 100644
--- a/erts/emulator/test/bs_construct_SUITE.erl
+++ b/erts/emulator/test/bs_construct_SUITE.erl
@@ -911,5 +911,31 @@ append_unit_8(Bin) ->
append_unit_16(Bin) ->
<<Bin/binary-unit:16,0:1>>.
-
+bs_add_overflow(Config) ->
+ case erlang:system_info(wordsize) of
+ 8 ->
+ {skip, "64-bit architecture"};
+ 4 ->
+ {'EXIT', {system_limit, _}} = (catch bs_add_overflow_signed()),
+ {'EXIT', {system_limit, _}} = (catch bs_add_overflow_unsigned()),
+ ok
+ end.
+
+bs_add_overflow_signed() ->
+ %% Produce a large result of bs_add that, if cast to signed int, would
+ %% overflow into a negative number that fits a smallnum.
+ Large = <<0:((1 bsl 30)-1)>>,
+ <<Large/bits, Large/bits, Large/bits, Large/bits,
+ Large/bits, Large/bits, Large/bits, Large/bits,
+ Large/bits>>.
+
+bs_add_overflow_unsigned() ->
+ %% Produce a large result of bs_add that goes beyond the limit of an
+ %% unsigned word. This used to succeed but produced an incorrect result
+ %% where B =:= C!
+ A = <<0:((1 bsl 32)-8)>>,
+ B = <<2, 3>>,
+ C = <<A/binary,1,B/binary>>,
+ true = byte_size(B) < byte_size(C).
+
id(I) -> I.