From: Peter van Dijk <peter.van.dijk@powerdns.com>
Date: Wed, 6 Jan 2021 16:17:00 +0000 (+0100)
Subject: lmdbbackend: avoid unaligned uint32_t reads by using memcpy
X-Git-Tag: rec-4.5.0-alpha1~34^2~3
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=f061d15d3289070750d7213c04cbd93fe6c5ec5c;p=thirdparty%2Fpdns.git

lmdbbackend: avoid unaligned uint32_t reads by using memcpy

lmdbbackend.cc:942:27: runtime error: load of misaligned address 0x604000b827aa for type 'uint32_t' (aka 'unsigned int'), which requires 4 byte alignment
---

diff --git a/modules/lmdbbackend/lmdbbackend.cc b/modules/lmdbbackend/lmdbbackend.cc
index 020a275f17..9cf2a90d8d 100644
--- a/modules/lmdbbackend/lmdbbackend.cc
+++ b/modules/lmdbbackend/lmdbbackend.cc
@@ -824,7 +824,10 @@ bool LMDBBackend::getDomainInfo(const DNSName &domain, DomainInfo &di, bool getS
       serFromString(val.get<string_view>(), rr);
 
       if(rr.content.size() >= 5 * sizeof(uint32_t)) {
-        uint32_t serial = *reinterpret_cast<uint32_t*>(&rr.content[rr.content.size() - (5 * sizeof(uint32_t))]);
+        uint32_t serial;
+        // a SOA has five 32 bit fields, the first of which is the serial
+        // there are two variable length names before the serial, so we calculate from the back
+        memcpy(&serial, &rr.content[rr.content.size() - (4 * sizeof(uint32_t))], sizeof(serial));
         di.serial = ntohl(serial);
       }
     }
@@ -939,7 +942,10 @@ void LMDBBackend::getAllDomains(vector<DomainInfo> *domains, bool include_disabl
       serFromString(val.get<string_view>(), rr);
 
       if(rr.content.size() >= 5 * sizeof(uint32_t)) {
-        uint32_t serial = *reinterpret_cast<uint32_t*>(&rr.content[rr.content.size() - (5 * sizeof(uint32_t))]);
+        uint32_t serial;
+        // a SOA has five 32 bit fields, the first of which is the serial
+        // there are two variable length names before the serial, so we calculate from the back
+        memcpy(&serial, &rr.content[rr.content.size() - (5 * sizeof(uint32_t))], sizeof(serial));
         di.serial = ntohl(serial);
       }
     } else if(!include_disabled) {