tests: Allow running tests under ASAN+UBSAN

memcpy() must not be called on a NULL pointer, even if the size is 0.
Furthermore, leak checks must be disabled to avoid wrong exit codes.
Finally, use clang if turning on sanitizers.  Otherwise, Fedora 39's
gcc-13.2.1-7.fc39.x86_64 package produces binaries that crash with
SIGSEGV.

libqrexec/Makefile

@@ -1,10 +1,11 @@
-CC=gcc
+CC ?=gcc
 VCHAN_PKG = $(if $(BACKEND_VMM),vchan-$(BACKEND_VMM),vchan)
 override QUBES_CFLAGS := -I. -I../libqrexec -g -O2 -Wall -Wextra -Werror \
    $(shell pkg-config --cflags $(VCHAN_PKG)) -fstack-protector \
    -D_FORTIFY_SOURCE=2 -fstack-protector-strong -fPIC -std=gnu11 -D_POSIX_C_SOURCE=200809L \
    -D_GNU_SOURCE $(CFLAGS) \
-   -Wstrict-prototypes -Wold-style-definition -Wmissing-declarations
+   -Wstrict-prototypes -Wold-style-definition -Wmissing-declarations \
+   -fno-delete-null-pointer-checks
 
 override LDFLAGS += -pie -Wl,-z,relro,-z,now -shared
 

libqrexec/buffer.c

@@ -23,6 +23,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <assert.h>
 #include "libqrexec-utils.h"
 
 #define BUFFER_LIMIT 50000000
@@ -79,6 +80,7 @@ void buffer_append(struct buffer *b, const char *data, int len)
 {
     int newsize;
     char *qdata;
+    assert(data != NULL && "NULL data");
     if (b->buflen < 0 || b->buflen > BUFFER_LIMIT) {
         LOG(ERROR, "buffer_append buflen %d", len);
         exit(1);
@@ -91,7 +93,9 @@ void buffer_append(struct buffer *b, const char *data, int len)
         return;
     newsize = len + b->buflen;
     qdata = limited_malloc(len + b->buflen);
-    memcpy(qdata, b->data, (size_t)b->buflen);
+    if (b->data != 0) {
+        memcpy(qdata, b->data, (size_t)b->buflen);
+    }
     memcpy(qdata + b->buflen, data, (size_t)len);
     buffer_free(b);
     b->buflen = newsize;

run-tests

@@ -5,8 +5,18 @@ if command -v dnf >/dev/null; then
     sudo dnf install python3dist\({coverage,pytest,gbulb,pyinotify,pytest-asyncio}\) || :
 fi
 if pkg-config vchan-socket; then
-    export CFLAGS="--coverage -DCOVERAGE"
-    export LDFLAGS=--coverage
+    if [[ -n "${USE_ASAN-}" ]]; then
+        export CFLAGS=-fsanitize=address,undefined
+        export LDFLAGS=-fsanitize=address,undefined
+        # MUST use clang here.  GCC causes random SIGSEGV crashes
+        # when ASAN and UBSAN is in use.  Release build (no sanitizers)
+        # works fine.
+        export CC=clang
+        export ASAN_OPTIONS=leak_check_at_exit=0
+    else
+        export CFLAGS="--coverage -DCOVERAGE"
+        export LDFLAGS=--coverage
+    fi
     make -C libqrexec BACKEND_VMM=socket clean all
     make -C agent BACKEND_VMM=socket clean all
     make -C daemon BACKEND_VMM=socket clean all