File 1061-erts-Fix-internal-hashing-entropy-for-maps... of Package erlang

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File 1061-erts-Fix-internal-hashing-entropy-for-maps.patch of Package erlang (Revision c589bc075ed79a918315277f2ca40bc8)

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From 249e3ec86de802232d17666a93665ae638cbc319 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn-Egil=20Dahlberg?= <egil@erlang.org>
Date: Thu, 21 Jul 2016 15:57:15 +0200
Subject: [PATCH 2/3] erts: Fix internal hashing entropy for maps

We need to use an initial hash seed for each map pair, i.e. the
hash value. The hash value is reset to the seed for each pair instead
of setting the seed to zero.

If we don't, no additional entropy is given to the system and the
hash collision resolution in maps:from_list/1 would fail.
---
 erts/emulator/beam/utils.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/erts/emulator/beam/utils.c b/erts/emulator/beam/utils.c
index 4dc7246..85647b8 100644
--- a/erts/emulator/beam/utils.c
+++ b/erts/emulator/beam/utils.c
@@ -1678,17 +1678,22 @@ make_internal_hash(Eterm term)
                      * the order in which keys and values are encountered.
                      * We therefore calculate context independent hashes for all    				      .
                      * key-value pairs and then xor them together.
+                     *
+                     * We *do* need to use an initial seed for each pair, i.e. the
+                     * hash value, so the hash value is reset for each pair with 'hash'.
+                     * If we don't, no additional entropy is given to the system and the
+                     * hash collision resolution in maps:from_list/1 would fail.
                      */
                     ESTACK_PUSH(s, hash_xor_pairs);
                     ESTACK_PUSH(s, hash);
                     ESTACK_PUSH(s, HASH_MAP_TAIL);
-                    hash = 0;
-                    hash_xor_pairs = 0;
                     for (i = size - 1; i >= 0; i--) {
+                        ESTACK_PUSH(s, hash); /* initial seed for all pairs */
                         ESTACK_PUSH(s, HASH_MAP_PAIR);
                         ESTACK_PUSH(s, vs[i]);
                         ESTACK_PUSH(s, ks[i]);
                     }
+                    hash_xor_pairs = 0;
                     goto pop_next;
                 }
                 case HAMT_SUBTAG_HEAD_ARRAY:
@@ -1700,7 +1705,6 @@ make_internal_hash(Eterm term)
                     ESTACK_PUSH(s, hash_xor_pairs);
                     ESTACK_PUSH(s, hash);
                     ESTACK_PUSH(s, HASH_MAP_TAIL);
-                    hash = 0;
                     hash_xor_pairs = 0;
                 }
                 switch (hdr & _HEADER_MAP_SUBTAG_MASK) {
@@ -1717,6 +1721,7 @@ make_internal_hash(Eterm term)
                 while (i) {
                     if (is_list(*ptr)) {
                         Eterm* cons = list_val(*ptr);
+                        ESTACK_PUSH(s, hash); /* initial seed for all pairs */
                         ESTACK_PUSH(s, HASH_MAP_PAIR);
                         ESTACK_PUSH(s, CDR(cons));
                         ESTACK_PUSH(s, CAR(cons));
@@ -1921,7 +1926,7 @@ make_internal_hash(Eterm term)
 		}
 		case HASH_MAP_PAIR:
 		    hash_xor_pairs ^= hash;
-		    hash = 0;
+		    hash = (Uint32) ESTACK_POP(s); /* initial seed for all pairs */
 		    goto pop_next;
 
 	        case HASH_CDR:
-- 
2.1.4

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File 1061-erts-Fix-internal-hashing-entropy-for-maps.patch of Package erlang (Revision c589bc075ed79a918315277f2ca40bc8)

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