From 8452404bd7facb89790c32bab508f55bf8d37cea Mon Sep 17 00:00:00 2001 From: Mark Andrews Date: Sat, 15 Aug 2020 10:12:50 +1000 Subject: [PATCH] A6: return FORMERR in fromwire if bits are non zero. oss_fuzz: Issue 24864: bind9:dns_rdata_fromwire_text_fuzzer: Overwrites-const-input in dns_rdata_fromwire_text_fuzzer --- lib/dns/rdata/in_1/a6_38.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/lib/dns/rdata/in_1/a6_38.c b/lib/dns/rdata/in_1/a6_38.c index ac721aad4c..d69c5d3dc2 100644 --- a/lib/dns/rdata/in_1/a6_38.c +++ b/lib/dns/rdata/in_1/a6_38.c @@ -182,7 +182,9 @@ fromwire_in_a6(ARGS_FROMWIRE) { return (ISC_R_UNEXPECTEDEND); } mask = 0xff >> (prefixlen % 8); - sr.base[0] &= mask; /* Ensure pad bits are zero. */ + if ((sr.base[0] & ~mask) != 0) { + return (DNS_R_FORMERR); + } RETERR(mem_tobuffer(target, sr.base, octets)); isc_buffer_forward(source, octets); }