[DFSan] Add custom wrapper for getsockname.

The wrapper clears shadow for any bytes written to addr or addrlen.

Reviewed By: stephan.yichao.zhao

Differential Revision: https://reviews.llvm.org/D92964

compiler-rt/lib/dfsan/dfsan_custom.cpp

@@ -927,6 +927,21 @@ SANITIZER_INTERFACE_ATTRIBUTE int __dfsw_getsockopt(
   return ret;
 }
 
+SANITIZER_INTERFACE_ATTRIBUTE int __dfsw_getsockname(
+    int sockfd, struct sockaddr *addr, socklen_t *addrlen,
+    dfsan_label sockfd_label, dfsan_label addr_label, dfsan_label addrlen_label,
+    dfsan_label *ret_label) {
+  socklen_t origlen = addrlen ? *addrlen : 0;
+  int ret = getsockname(sockfd, addr, addrlen);
+  if (ret != -1 && addr && addrlen) {
+    socklen_t written_bytes = origlen < *addrlen ? origlen : *addrlen;
+    dfsan_set_label(0, addrlen, sizeof(*addrlen));
+    dfsan_set_label(0, addr, written_bytes);
+  }
+  *ret_label = 0;
+  return ret;
+}
+
 // Type of the trampoline function passed to the custom version of
 // dfsan_set_write_callback.
 typedef void (*write_trampoline_t)(

compiler-rt/lib/dfsan/done_abilist.txt

@@ -194,6 +194,7 @@ fun:get_current_dir_name=custom
 fun:gethostname=custom
 fun:getrlimit=custom
 fun:getrusage=custom
+fun:getsockname=custom
 fun:getsockopt=custom
 fun:nanosleep=custom
 fun:pread=custom

compiler-rt/test/dfsan/custom.cpp

@@ -931,6 +931,26 @@ void test_socketpair() {
   ASSERT_READ_ZERO_LABEL(fd, sizeof(fd));
 }
 
+void test_getsockname() {
+  int sockfd = socket(AF_UNIX, SOCK_DGRAM, 0);
+  assert(sockfd != -1);
+
+  struct sockaddr addr = {};
+  socklen_t addrlen = sizeof(addr);
+  dfsan_set_label(i_label, &addr, addrlen);
+  dfsan_set_label(i_label, &addrlen, sizeof(addrlen));
+
+  int ret = getsockname(sockfd, &addr, &addrlen);
+  assert(ret != -1);
+  ASSERT_ZERO_LABEL(ret);
+  ASSERT_ZERO_LABEL(addrlen);
+  assert(addrlen < sizeof(addr));
+  ASSERT_READ_ZERO_LABEL(&addr, addrlen);
+  ASSERT_READ_LABEL(((char *)&addr) + addrlen, 1, i_label);
+
+  close(sockfd);
+}
+
 void test_getsockopt() {
   int sockfd = socket(AF_UNIX, SOCK_DGRAM, 0);
   assert(sockfd != -1);
@@ -1134,6 +1154,7 @@ int main(void) {
   test_getpwuid_r();
   test_getrlimit();
   test_getrusage();
+  test_getsockname();
   test_getsockopt();
   test_gettimeofday();
   test_inet_pton();