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bpo-28055: Fix unaligned accesses in siphash24(). (GH-6123) 

The hash implementation casts the input pointer to uint64_t* and directly reads
from this, which may cause unaligned accesses. Use memcpy() instead so this code
will not crash with SIGBUS on sparc.

https://bugs.gentoo.org/show_bug.cgi?id=636400
(cherry picked from commit 1e2ec8a996)

Co-authored-by: Rolf Eike Beer <eike@sf-mail.de>
This commit is contained in:
Miss Islington (bot) 2018-05-13 04:17:07 -07:00 committed by GitHub
parent 6e9456e4f6
commit 8ed545f6de
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2 changed files with 14 additions and 13 deletions
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1
Misc/NEWS.d/next/Core and Builtins/2018-04-25-20-44-42.bpo-28055.f49kfC.rst Normal file
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@ -0,0 +1 @@
Fix unaligned accesses in siphash24(). Patch by Rolf Eike Beer.

26
Python/pyhash.c
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@ -366,7 +366,7 @@ static PyHash_FuncDef PyHash_Func = {fnv, "fnv", 8 * SIZEOF_PY_HASH_T,
static uint64_t
siphash24(uint64_t k0, uint64_t k1, const void *src, Py_ssize_t src_sz) {
uint64_t b = (uint64_t)src_sz << 56;
const uint64_t *in = (uint64_t*)src;
const uint8_t *in = (uint8_t*)src;
uint64_t v0 = k0 ^ 0x736f6d6570736575ULL;
uint64_t v1 = k1 ^ 0x646f72616e646f6dULL;
@ -375,12 +375,13 @@ siphash24(uint64_t k0, uint64_t k1, const void *src, Py_ssize_t src_sz) {
uint64_t t;
uint8_t *pt;
uint8_t *m;
while (src_sz >= 8) {
uint64_t mi = _le64toh(*in);
in += 1;
src_sz -= 8;
uint64_t mi;
memcpy(&mi, in, sizeof(mi));
mi = _le64toh(mi);
in += sizeof(mi);
src_sz -= sizeof(mi);
v3 ^= mi;
DOUBLE_ROUND(v0,v1,v2,v3);
v0 ^= mi;
@ -388,15 +389,14 @@ siphash24(uint64_t k0, uint64_t k1, const void *src, Py_ssize_t src_sz) {
t = 0;
pt = (uint8_t *)&t;
m = (uint8_t *)in;
switch (src_sz) {
case 7: pt[6] = m[6]; /* fall through */
case 6: pt[5] = m[5]; /* fall through */
case 5: pt[4] = m[4]; /* fall through */
case 4: memcpy(pt, m, sizeof(uint32_t)); break;
case 3: pt[2] = m[2]; /* fall through */
case 2: pt[1] = m[1]; /* fall through */
case 1: pt[0] = m[0]; /* fall through */
case 7: pt[6] = in[6]; /* fall through */
case 6: pt[5] = in[5]; /* fall through */
case 5: pt[4] = in[4]; /* fall through */
case 4: memcpy(pt, in, sizeof(uint32_t)); break;
case 3: pt[2] = in[2]; /* fall through */
case 2: pt[1] = in[1]; /* fall through */
case 1: pt[0] = in[0]; /* fall through */
}
b |= _le64toh(t);