From 0fdc09efb6c3b5c6b56f9a0d8b79f9215d3bce3d Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Ond=C5=99ej=20Sur=C3=BD?= Date: Wed, 25 Mar 2020 17:25:45 +0100 Subject: [PATCH] Fix 'Dereference of null pointer' from scan-build-10 These are mostly false positives, the clang-analyzer FAQ[1] specifies why and how to fix it: > The reason the analyzer often thinks that a pointer can be null is > because the preceding code checked compared it against null. So if you > are absolutely sure that it cannot be null, remove the preceding check > and, preferably, add an assertion as well. The 4 warnings reported are: dnssec-cds.c:781:4: warning: Access to field 'base' results in a dereference of a null pointer (loaded from variable 'buf') isc_buffer_availableregion(buf, &r); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ /builds/isc-projects/bind9/lib/isc/include/isc/buffer.h:996:36: note: expanded from macro 'isc_buffer_availableregion' ^ /builds/isc-projects/bind9/lib/isc/include/isc/buffer.h:821:16: note: expanded from macro 'ISC__BUFFER_AVAILABLEREGION' (_r)->base = isc_buffer_used(_b); \ ^~~~~~~~~~~~~~~~~~~ /builds/isc-projects/bind9/lib/isc/include/isc/buffer.h:152:29: note: expanded from macro 'isc_buffer_used' ((void *)((unsigned char *)(b)->base + (b)->used)) /*d*/ ^~~~~~~~~ 1 warning generated. -- byname_test.c:308:34: warning: Access to field 'fwdtable' results in a dereference of a null pointer (loaded from variable 'view') RUNTIME_CHECK(dns_fwdtable_add(view->fwdtable, dns_rootname, ^~~~~~~~~~~~~~ /builds/isc-projects/bind9/lib/isc/include/isc/util.h:318:52: note: expanded from macro 'RUNTIME_CHECK' ^~~~ /builds/isc-projects/bind9/lib/isc/include/isc/error.h:50:21: note: expanded from macro 'ISC_ERROR_RUNTIMECHECK' ((void)(ISC_LIKELY(cond) || \ ^~~~ /builds/isc-projects/bind9/lib/isc/include/isc/likely.h:23:43: note: expanded from macro 'ISC_LIKELY' ^ 1 warning generated. -- ./rndc.c:255:6: warning: Dereference of null pointer (loaded from variable 'host') if (*host == '/') { ^~~~~ 1 warning generated. -- ./main.c:1254:9: warning: Access to field 'sctx' results in a dereference of a null pointer (loaded from variable 'named_g_server') sctx = named_g_server->sctx; ^~~~~~~~~~~~~~~~~~~~ 1 warning generated. References: 1. https://clang-analyzer.llvm.org/faq.html#null_pointer (cherry picked from commit ddd0d356e5922e6b1958b3050e04a160e106734a) --- bin/dnssec/dnssec-cds.c | 4 ++++ bin/named/main.c | 1 + bin/rndc/rndc.c | 4 +++- bin/tests/optional/byname_test.c | 1 + 4 files changed, 9 insertions(+), 1 deletion(-) diff --git a/bin/dnssec/dnssec-cds.c b/bin/dnssec/dnssec-cds.c index e94235786c..a9ba59d4f2 100644 --- a/bin/dnssec/dnssec-cds.c +++ b/bin/dnssec/dnssec-cds.c @@ -754,6 +754,8 @@ ds_from_cds(dns_rdatalist_t *dslist, isc_buffer_t *buf, dns_rdata_t *cds) { dns_rdata_ds_t ds; dns_rdata_t *rdata; + REQUIRE(buf != NULL); + rdata = rdata_get(); result = dns_rdata_tostruct(cds, &ds, NULL); @@ -772,6 +774,8 @@ ds_from_cdnskey(dns_rdatalist_t *dslist, isc_buffer_t *buf, isc_result_t result; unsigned i, n; + REQUIRE(buf != NULL); + n = sizeof(dtype) / sizeof(dtype[0]); for (i = 0; i < n; i++) { if (dtype[i] != 0) { diff --git a/bin/named/main.c b/bin/named/main.c index 603e8a1b5e..50345be562 100644 --- a/bin/named/main.c +++ b/bin/named/main.c @@ -1291,6 +1291,7 @@ setup(void) { #endif /* if CONTRIB_DLZ */ named_server_create(named_g_mctx, &named_g_server); + ENSURE(named_g_server != NULL); sctx = named_g_server->sctx; /* diff --git a/bin/rndc/rndc.c b/bin/rndc/rndc.c index b6e7a18664..f238b1d584 100644 --- a/bin/rndc/rndc.c +++ b/bin/rndc/rndc.c @@ -252,6 +252,8 @@ get_addresses(const char *host, in_port_t port) { isc_result_t result; int found = 0, count; + REQUIRE(host != NULL); + if (*host == '/') { result = isc_sockaddr_frompath(&serveraddrs[nserveraddrs], host); @@ -1036,7 +1038,7 @@ main(int argc, char **argv) { fatal("'%s' is not implemented", command); } - if (nserveraddrs == 0) { + if (nserveraddrs == 0 && servername != NULL) { get_addresses(servername, (in_port_t)remoteport); } diff --git a/bin/tests/optional/byname_test.c b/bin/tests/optional/byname_test.c index a80160a690..1d6ab599c1 100644 --- a/bin/tests/optional/byname_test.c +++ b/bin/tests/optional/byname_test.c @@ -305,6 +305,7 @@ main(int argc, char *argv[]) { isc_sockaddr_fromin(&sa, &ina, 53); ISC_LIST_APPEND(sal, &sa, link); + REQUIRE(DNS_VIEW_VALID(view)); RUNTIME_CHECK(dns_fwdtable_add(view->fwdtable, dns_rootname, &sal, dns_fwdpolicy_only) == ISC_R_SUCCESS); -- GitLab