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Fix excessive memory allocation from crafted container headers #409

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Merged
byroot merged 1 commit into from
Oct 11, 2026
Merged

Fix excessive memory allocation from crafted container headers #409

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20 changes: 12 additions & 8 deletions ext/msgpack/unpacker.c
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Original file line number Diff line number Diff line change
Expand Up @@ -74,9 +74,13 @@ static inline VALUE rb_hash_new_capa_inline(long capa)
#define rb_hash_new_capa rb_hash_new_capa_inline
#endif

static inline int16_t initial_buffer_size(long size)
static inline int16_t initial_buffer_size(msgpack_unpacker_t* uk, long count, size_t bytes_per_element)
{
return (size > INITIAL_BUFFER_CAPACITY_MAX) ? INITIAL_BUFFER_CAPACITY_MAX : size;
size_t available = msgpack_buffer_all_readable_size(UNPACKER_BUFFER_(uk)) / bytes_per_element;
if((size_t)count > available) {
count = (long)available;
}
return (count > INITIAL_BUFFER_CAPACITY_MAX) ? INITIAL_BUFFER_CAPACITY_MAX : count;
}

void msgpack_unpacker_static_init(void)
Expand Down Expand Up @@ -481,14 +485,14 @@ static int read_primitive(msgpack_unpacker_t* uk)
if(count == 0) {
return object_complete(uk, rb_ary_new());
}
return _msgpack_unpacker_stack_push(uk, STACK_TYPE_ARRAY, count, rb_ary_new2(initial_buffer_size(count)));
return _msgpack_unpacker_stack_push(uk, STACK_TYPE_ARRAY, count, rb_ary_new2(initial_buffer_size(uk, count, 1)));

SWITCH_RANGE(b, 0x80, 0x8f) // FixMap
int count = b & 0x0f;
if(count == 0) {
return object_complete(uk, rb_hash_new());
}
return _msgpack_unpacker_stack_push(uk, STACK_TYPE_MAP_KEY, count*2, rb_hash_new_capa(initial_buffer_size(count)));
return _msgpack_unpacker_stack_push(uk, STACK_TYPE_MAP_KEY, count*2, rb_hash_new_capa(initial_buffer_size(uk, count, 2)));

SWITCH_RANGE(b, 0xc0, 0xdf) // Variable
switch(b) {
Expand Down Expand Up @@ -711,7 +715,7 @@ static int read_primitive(msgpack_unpacker_t* uk)
if(count == 0) {
return object_complete(uk, rb_ary_new());
}
return _msgpack_unpacker_stack_push(uk, STACK_TYPE_ARRAY, count, rb_ary_new2(initial_buffer_size(count)));
return _msgpack_unpacker_stack_push(uk, STACK_TYPE_ARRAY, count, rb_ary_new2(initial_buffer_size(uk, count, 1)));
}

case 0xdd: // array 32
Expand All @@ -721,7 +725,7 @@ static int read_primitive(msgpack_unpacker_t* uk)
if(count == 0) {
return object_complete(uk, rb_ary_new());
}
return _msgpack_unpacker_stack_push(uk, STACK_TYPE_ARRAY, count, rb_ary_new2(initial_buffer_size(count)));
return _msgpack_unpacker_stack_push(uk, STACK_TYPE_ARRAY, count, rb_ary_new2(initial_buffer_size(uk, count, 1)));
}

case 0xde: // map 16
Expand All @@ -731,7 +735,7 @@ static int read_primitive(msgpack_unpacker_t* uk)
if(count == 0) {
return object_complete(uk, rb_hash_new());
}
return _msgpack_unpacker_stack_push(uk, STACK_TYPE_MAP_KEY, count*2, rb_hash_new_capa(initial_buffer_size(count)));
return _msgpack_unpacker_stack_push(uk, STACK_TYPE_MAP_KEY, count*2, rb_hash_new_capa(initial_buffer_size(uk, count, 2)));
}

case 0xdf: // map 32
Expand All @@ -741,7 +745,7 @@ static int read_primitive(msgpack_unpacker_t* uk)
if(count == 0) {
return object_complete(uk, rb_hash_new());
}
return _msgpack_unpacker_stack_push(uk, STACK_TYPE_MAP_KEY, count*2, rb_hash_new_capa(initial_buffer_size(count)));
return _msgpack_unpacker_stack_push(uk, STACK_TYPE_MAP_KEY, count*2, rb_hash_new_capa(initial_buffer_size(uk, count, 2)));
}

default:
Expand Down
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