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py/objarray: Fix amount of free space in array when doing slice assign. 

Prior to this patch the amount of free space in an array (including
bytearray) was not being maintained correctly for the case of slice
assignment which changed the size of the array.  Under certain cases (as
encoded in the new test) it was possible that the array could grow beyond
its allocated memory block and corrupt the heap.

Fixes issue #4127.
This commit is contained in:
Damien George 2019-08-15 23:02:04 +10:00
parent baeebc557c
commit acfbb9febd
2 changed files with 9 additions and 1 deletions
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3
py/objarray.c
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@ -445,7 +445,7 @@ STATIC mp_obj_t array_subscr(mp_obj_t self_in, mp_obj_t index_in, mp_obj_t value
if (len_adj > o->free) { if (len_adj > o->free) {
// TODO: alloc policy; at the moment we go conservative // TODO: alloc policy; at the moment we go conservative
o->items = m_renew(byte, o->items, (o->len + o->free) * item_sz, (o->len + len_adj) * item_sz); o->items = m_renew(byte, o->items, (o->len + o->free) * item_sz, (o->len + len_adj) * item_sz);
o->free = 0; o->free = len_adj;
dest_items = o->items; dest_items = o->items;
} }
mp_seq_replace_slice_grow_inplace(dest_items, o->len, mp_seq_replace_slice_grow_inplace(dest_items, o->len,
@ -458,6 +458,7 @@ STATIC mp_obj_t array_subscr(mp_obj_t self_in, mp_obj_t index_in, mp_obj_t value
mp_seq_clear(dest_items, o->len + len_adj, o->len, item_sz); mp_seq_clear(dest_items, o->len + len_adj, o->len, item_sz);
// TODO: alloc policy after shrinking // TODO: alloc policy after shrinking
} }
o->free -= len_adj;
o->len += len_adj; o->len += len_adj;
return mp_const_none; return mp_const_none;
#else #else

7
tests/basics/bytearray_slice_assign.py
View File

@ -59,3 +59,10 @@ print(b)
b = bytearray(2) b = bytearray(2)
b[1:1] = b"12345" b[1:1] = b"12345"
print(b) print(b)
# Growth of bytearray via slice extension
b = bytearray(b'12345678')
b.append(57) # expand and add a bit of unused space at end of the bytearray
for i in range(400):
b[-1:] = b'ab' # grow slowly into the unused space
print(len(b), b)