diff --git a/compiler-rt/lib/dfsan/dfsan_custom.cpp b/compiler-rt/lib/dfsan/dfsan_custom.cpp
--- a/compiler-rt/lib/dfsan/dfsan_custom.cpp
+++ b/compiler-rt/lib/dfsan/dfsan_custom.cpp
@@ -799,6 +799,16 @@
   return ret;
 }
 
+SANITIZER_INTERFACE_ATTRIBUTE
+int __dfsw_sigaltstack(const stack_t *ss, stack_t *old_ss, dfsan_label ss_label,
+                       dfsan_label old_ss_label, dfsan_label *ret_label) {
+  int ret = sigaltstack(ss, old_ss);
+  if (ret != -1 && old_ss)
+    dfsan_set_label(0, old_ss, sizeof(*old_ss));
+  *ret_label = 0;
+  return ret;
+}
+
 SANITIZER_INTERFACE_ATTRIBUTE
 int __dfsw_gettimeofday(struct timeval *tv, struct timezone *tz,
                         dfsan_label tv_label, dfsan_label tz_label,
diff --git a/compiler-rt/lib/dfsan/done_abilist.txt b/compiler-rt/lib/dfsan/done_abilist.txt
--- a/compiler-rt/lib/dfsan/done_abilist.txt
+++ b/compiler-rt/lib/dfsan/done_abilist.txt
@@ -200,6 +200,7 @@
 fun:pread=custom
 fun:read=custom
 fun:recvmsg=custom
+fun:sigaltstack=custom
 fun:socketpair=custom
 fun:stat=custom
 fun:time=custom
diff --git a/compiler-rt/test/dfsan/custom.cpp b/compiler-rt/test/dfsan/custom.cpp
--- a/compiler-rt/test/dfsan/custom.cpp
+++ b/compiler-rt/test/dfsan/custom.cpp
@@ -762,6 +762,15 @@
   ASSERT_READ_ZERO_LABEL(&oldact, sizeof(oldact));
 }
 
+void test_sigaltstack() {
+  stack_t old_altstack = {};
+  dfsan_set_label(j_label, &old_altstack, sizeof(old_altstack));
+  int ret = sigaltstack(NULL, &old_altstack);
+  assert(ret == 0);
+  ASSERT_ZERO_LABEL(ret);
+  ASSERT_READ_ZERO_LABEL(&old_altstack, sizeof(old_altstack));
+}
+
 void test_gettimeofday() {
   struct timeval tv;
   struct timezone tz;
@@ -1172,6 +1181,7 @@
   test_sched_getaffinity();
   test_select();
   test_sigaction();
+  test_sigaltstack();
   test_sigemptyset();
   test_snprintf();
   test_socketpair();