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[3.7] bpo-33312: Fix clang ubsan out of bounds warnings in dict. (GH-6537) #6543

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Merged
merged 1 commit into from
Apr 20, 2018
Merged

[3.7] bpo-33312: Fix clang ubsan out of bounds warnings in dict. (GH-6537) #6543

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3 changes: 3 additions & 0 deletions Misc/NEWS.d/next/Core and Builtins/2018-04-19-08-30-07.bpo-33312.mDe2iL.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,3 @@
Fixed clang ubsan (undefined behavior sanitizer) warnings in dictobject.c by
adjusting how the internal struct _dictkeysobject shared keys structure is
declared.
11 changes: 2 additions & 9 deletions Objects/dict-common.h
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Expand Up @@ -58,15 +58,8 @@ struct _dictkeysobject {
- 4 bytes if dk_size <= 0xffffffff (int32_t*)
- 8 bytes otherwise (int64_t*)

Dynamically sized, 8 is minimum. */
union {
int8_t as_1[8];
int16_t as_2[4];
int32_t as_4[2];
#if SIZEOF_VOID_P > 4
int64_t as_8[1];
#endif
} dk_indices;
Dynamically sized, SIZEOF_VOID_P is minimum. */
char dk_indices[]; /* char is required to avoid strict aliasing. */

/* "PyDictKeyEntry dk_entries[dk_usable];" array follows:
see the DK_ENTRIES() macro */
Expand Down
27 changes: 12 additions & 15 deletions Objects/dictobject.c
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Expand Up @@ -298,7 +298,7 @@ PyDict_Fini(void)
2 : sizeof(int32_t))
#endif
#define DK_ENTRIES(dk) \
((PyDictKeyEntry*)(&(dk)->dk_indices.as_1[DK_SIZE(dk) * DK_IXSIZE(dk)]))
((PyDictKeyEntry*)(&((int8_t*)((dk)->dk_indices))[DK_SIZE(dk) * DK_IXSIZE(dk)]))

#define DK_DEBUG_INCREF _Py_INC_REFTOTAL _Py_REF_DEBUG_COMMA
#define DK_DEBUG_DECREF _Py_DEC_REFTOTAL _Py_REF_DEBUG_COMMA
Expand All @@ -316,21 +316,21 @@ dk_get_index(PyDictKeysObject *keys, Py_ssize_t i)
Py_ssize_t ix;

if (s <= 0xff) {
int8_t *indices = keys->dk_indices.as_1;
int8_t *indices = (int8_t*)(keys->dk_indices);
ix = indices[i];
}
else if (s <= 0xffff) {
int16_t *indices = keys->dk_indices.as_2;
int16_t *indices = (int16_t*)(keys->dk_indices);
ix = indices[i];
}
#if SIZEOF_VOID_P > 4
else if (s > 0xffffffff) {
int64_t *indices = keys->dk_indices.as_8;
int64_t *indices = (int64_t*)(keys->dk_indices);
ix = indices[i];
}
#endif
else {
int32_t *indices = keys->dk_indices.as_4;
int32_t *indices = (int32_t*)(keys->dk_indices);
ix = indices[i];
}
assert(ix >= DKIX_DUMMY);
Expand All @@ -346,23 +346,23 @@ dk_set_index(PyDictKeysObject *keys, Py_ssize_t i, Py_ssize_t ix)
assert(ix >= DKIX_DUMMY);

if (s <= 0xff) {
int8_t *indices = keys->dk_indices.as_1;
int8_t *indices = (int8_t*)(keys->dk_indices);
assert(ix <= 0x7f);
indices[i] = (char)ix;
}
else if (s <= 0xffff) {
int16_t *indices = keys->dk_indices.as_2;
int16_t *indices = (int16_t*)(keys->dk_indices);
assert(ix <= 0x7fff);
indices[i] = (int16_t)ix;
}
#if SIZEOF_VOID_P > 4
else if (s > 0xffffffff) {
int64_t *indices = keys->dk_indices.as_8;
int64_t *indices = (int64_t*)(keys->dk_indices);
indices[i] = ix;
}
#endif
else {
int32_t *indices = keys->dk_indices.as_4;
int32_t *indices = (int32_t*)(keys->dk_indices);
assert(ix <= 0x7fffffff);
indices[i] = (int32_t)ix;
}
Expand Down Expand Up @@ -421,8 +421,8 @@ static PyDictKeysObject empty_keys_struct = {
lookdict_split, /* dk_lookup */
0, /* dk_usable (immutable) */
0, /* dk_nentries */
.dk_indices = { .as_1 = {DKIX_EMPTY, DKIX_EMPTY, DKIX_EMPTY, DKIX_EMPTY,
DKIX_EMPTY, DKIX_EMPTY, DKIX_EMPTY, DKIX_EMPTY}},
{DKIX_EMPTY, DKIX_EMPTY, DKIX_EMPTY, DKIX_EMPTY,
DKIX_EMPTY, DKIX_EMPTY, DKIX_EMPTY, DKIX_EMPTY}, /* dk_indices */
};

static PyObject *empty_values[1] = { NULL };
Expand Down Expand Up @@ -530,7 +530,6 @@ static PyDictKeysObject *new_keys_object(Py_ssize_t size)
}
else {
dk = PyObject_MALLOC(sizeof(PyDictKeysObject)
- Py_MEMBER_SIZE(PyDictKeysObject, dk_indices)
+ es * size
+ sizeof(PyDictKeyEntry) * usable);
if (dk == NULL) {
Expand All @@ -543,7 +542,7 @@ static PyDictKeysObject *new_keys_object(Py_ssize_t size)
dk->dk_usable = usable;
dk->dk_lookup = lookdict_unicode_nodummy;
dk->dk_nentries = 0;
memset(&dk->dk_indices.as_1[0], 0xff, es * size);
memset(&dk->dk_indices[0], 0xff, es * size);
memset(DK_ENTRIES(dk), 0, sizeof(PyDictKeyEntry) * usable);
return dk;
}
Expand Down Expand Up @@ -3007,7 +3006,6 @@ _PyDict_SizeOf(PyDictObject *mp)
in the type object. */
if (mp->ma_keys->dk_refcnt == 1)
res += (sizeof(PyDictKeysObject)
- Py_MEMBER_SIZE(PyDictKeysObject, dk_indices)
+ DK_IXSIZE(mp->ma_keys) * size
+ sizeof(PyDictKeyEntry) * usable);
return res;
Expand All @@ -3017,7 +3015,6 @@ Py_ssize_t
_PyDict_KeysSize(PyDictKeysObject *keys)
{
return (sizeof(PyDictKeysObject)
- Py_MEMBER_SIZE(PyDictKeysObject, dk_indices)
+ DK_IXSIZE(keys) * DK_SIZE(keys)
+ USABLE_FRACTION(DK_SIZE(keys)) * sizeof(PyDictKeyEntry));
}
Expand Down