From 8a82bffe927e8928e304b9610a75ea07b0c4a798 Mon Sep 17 00:00:00 2001 From: Eric Wong Date: Tue, 9 Aug 2011 01:29:43 +0000 Subject: ext/json/generator/generator.c: prevent GC of temporary strings We need to guard temporary strings from being collected while we append to the JSON buffer (which may allocate memory). The RSTRING_PAIR macro is dangerous since it preserves no pointer to the original string VALUE, allowing GC to reap the object while we're still using the (C) string pointer. The included test case shows data corruption with large Bignums without this fix. --- ext/json/ext/generator/generator.c | 16 +++++++++++++--- ext/json/ext/generator/generator.h | 2 -- tests/test_json_generate.rb | 13 +++++++++++++ 3 files changed, 26 insertions(+), 5 deletions(-) diff --git a/ext/json/ext/generator/generator.c b/ext/json/ext/generator/generator.c index 4e44178..a75118a 100644 --- a/ext/json/ext/generator/generator.c +++ b/ext/json/ext/generator/generator.c @@ -349,6 +349,16 @@ static void fbuffer_append(FBuffer *fb, const char *newstr, unsigned long len) } } +static void fbuffer_append_str(FBuffer *fb, VALUE str) +{ + const char *newstr = RSTRING_PTR(str); + unsigned long len = RSTRING_LEN(str); + + RB_GC_GUARD(str); + + fbuffer_append(fb, newstr, len); +} + static void fbuffer_append_char(FBuffer *fb, char newchr) { fbuffer_inc_capa(fb, 1); @@ -852,7 +862,7 @@ static void generate_json_fixnum(FBuffer *buffer, VALUE Vstate, JSON_Generator_S static void generate_json_bignum(FBuffer *buffer, VALUE Vstate, JSON_Generator_State *state, VALUE obj) { VALUE tmp = rb_funcall(obj, i_to_s, 0); - fbuffer_append(buffer, RSTRING_PAIR(tmp)); + fbuffer_append_str(buffer, tmp); } static void generate_json_float(FBuffer *buffer, VALUE Vstate, JSON_Generator_State *state, VALUE obj) @@ -869,7 +879,7 @@ static void generate_json_float(FBuffer *buffer, VALUE Vstate, JSON_Generator_St rb_raise(eGeneratorError, "%u: %s not allowed in JSON", __LINE__, StringValueCStr(tmp)); } } - fbuffer_append(buffer, RSTRING_PAIR(tmp)); + fbuffer_append_str(buffer, tmp); } static void generate_json(FBuffer *buffer, VALUE Vstate, JSON_Generator_State *state, VALUE obj) @@ -897,7 +907,7 @@ static void generate_json(FBuffer *buffer, VALUE Vstate, JSON_Generator_State *s } else if (rb_respond_to(obj, i_to_json)) { tmp = rb_funcall(obj, i_to_json, 1, Vstate); Check_Type(tmp, T_STRING); - fbuffer_append(buffer, RSTRING_PAIR(tmp)); + fbuffer_append_str(buffer, tmp); } else { tmp = rb_funcall(obj, i_to_s, 0); Check_Type(tmp, T_STRING); diff --git a/ext/json/ext/generator/generator.h b/ext/json/ext/generator/generator.h index ee496fe..2a83149 100644 --- a/ext/json/ext/generator/generator.h +++ b/ext/json/ext/generator/generator.h @@ -45,8 +45,6 @@ #define RSTRING_LEN(string) RSTRING(string)->len #endif -#define RSTRING_PAIR(string) RSTRING_PTR(string), RSTRING_LEN(string) - /* fbuffer implementation */ typedef struct FBufferStruct { diff --git a/tests/test_json_generate.rb b/tests/test_json_generate.rb index 9b0cff4..bc4e395 100755 --- a/tests/test_json_generate.rb +++ b/tests/test_json_generate.rb @@ -177,4 +177,17 @@ EOT assert_raises(JSON::NestingError) { ary.to_json(s) } assert_equal 19, s.depth end + + def test_gc + bignum_too_long_to_embed_as_string = 1234567890123456789012345 + expect = bignum_too_long_to_embed_as_string.to_s + stress, GC.stress = GC.stress, true + + 10.times do |i| + tmp = bignum_too_long_to_embed_as_string.to_json + assert_equal expect, tmp + end + ensure + GC.stress = stress + end if GC.respond_to?(:stress=) end -- cgit v1.2.3-24-ge0c7