[sanitizer] Use res instead of len as a third parameter in COMMON_INTERCEPTOR_WRITE_RANGE in recv and recvfrom interceptors.

[m.ostapenko]

Summary

We should pass res as third parameter to COMMON_INTERCEPTOR_WRITE_RANGE , not len, because otherwise we can write to unrelated memory (in MSan) or get wrong report (in ASan);

[dvyukov]

LGTM

compiler-rt/trunk/lib/sanitizer_common/sanitizer_common_interceptors.inc

 
 #if SANITIZER_INTERCEPT_RECV_RECVFROM
 INTERCEPTOR(SSIZE_T, recv, int fd, void *buf, SIZE_T len, int flags) {
   void *ctx;
   COMMON_INTERCEPTOR_ENTER(ctx, recv, fd, buf, len, flags);
   COMMON_INTERCEPTOR_FD_ACCESS(ctx, fd);
   SSIZE_T res = REAL(recv)(fd, buf, len, flags);
   if (res > 0) {
-    COMMON_INTERCEPTOR_WRITE_RANGE(ctx, buf, len);
+    COMMON_INTERCEPTOR_WRITE_RANGE(ctx, buf, res);
   }
   if (res >= 0 && fd >= 0) COMMON_INTERCEPTOR_FD_ACQUIRE(ctx, fd);
   return res;
 }
 
 INTERCEPTOR(SSIZE_T, recvfrom, int fd, void *buf, SIZE_T len, int flags,
             void *srcaddr, int *addrlen) {
   void *ctx;
   COMMON_INTERCEPTOR_ENTER(ctx, recvfrom, fd, buf, len, flags, srcaddr,
                            addrlen);
   COMMON_INTERCEPTOR_FD_ACCESS(ctx, fd);
   SIZE_T srcaddr_sz;
   if (srcaddr) srcaddr_sz = *addrlen;
   SSIZE_T res = REAL(recvfrom)(fd, buf, len, flags, srcaddr, addrlen);
   if (res > 0) {
-    COMMON_INTERCEPTOR_WRITE_RANGE(ctx, buf, len);
+    COMMON_INTERCEPTOR_WRITE_RANGE(ctx, buf, res);
     if (srcaddr)
       COMMON_INTERCEPTOR_INITIALIZE_RANGE(srcaddr,
                                           Min((SIZE_T)*addrlen, srcaddr_sz));
   }
   return res;
 }
 #define INIT_RECV_RECVFROM          \
   COMMON_INTERCEPT_FUNCTION(recv);  \

compiler-rt/trunk/test/asan/TestCases/Linux/recvfrom.cc

static void *server_thread_udp(void *data) {
   serveraddr.sin_family = AF_INET;
   serveraddr.sin_addr.s_addr = htonl(INADDR_ANY);
   serveraddr.sin_port = htons(kPortNum);
 
   if (bind(sockfd, (struct sockaddr *) &serveraddr, sizeof(serveraddr)) < 0)
     fprintf(stderr, "ERROR on binding\n");
 
   recvfrom(sockfd, buf, kBufSize, 0, NULL, NULL); // BOOM
-  // CHECK: {{WRITE of size 10 at 0x.* thread T1}}
+  // CHECK: {{WRITE of size 9 at 0x.* thread T1}}
   // CHECK: {{    #1 0x.* in server_thread_udp.*recvfrom.cc:}}[[@LINE-2]]
   // CHECK: {{Address 0x.* is located in stack of thread T1 at offset}}
   // CHECK-NEXT: in{{.*}}server_thread_udp{{.*}}recvfrom.cc
   return NULL;
 }
 
 int main() {
   char buf[kBufSize] = "123456789";