fix resize window crash and slightly more performant timed_read

docs/Changelog.md

@@ -18,6 +18,7 @@ sending a mail to <afl-users+subscribe@googlegroups.com>.
        a temporary main node until a real main nodes shows up
      - switched murmur2 hashing and random() for xxh3 and xoshiro256**, giving up to 5.5% speed
        increase
+     - Resizing the window does not crash afl-fuzz anymore
      - fix/update to MOpt (thanks to arnow117)
      - added MOpt dictionary support from repo
   - llvm_mode:

src/afl-forkserver.c

@@ -132,7 +132,8 @@ static u32 read_s32_timed(s32 fd, s32 *buf, u32 timeout_ms,
   FD_ZERO(&readfds);
   FD_SET(fd, &readfds);
   struct timeval timeout;
-  size_t         len = 4;
+  int            sret;
+  ssize_t        len_read;
 
   timeout.tv_sec = (timeout_ms / 1000);
   timeout.tv_usec = (timeout_ms % 1000) * 1000;
@@ -141,26 +142,19 @@ static u32 read_s32_timed(s32 fd, s32 *buf, u32 timeout_ms,
 #endif
 
   /* set exceptfds as well to return when a child exited/closed the pipe. */
-  int sret = select(fd + 1, &readfds, NULL, NULL, &timeout);
+restart_select:
+  sret = select(fd + 1, &readfds, NULL, NULL, &timeout);
 
-  if (!sret) {
+  if (likely(sret > 0)) {
 
-    *buf = -1;
-    return timeout_ms + 1;
+  restart_read:
+    len_read = read(fd, (u8 *)buf, 4);
 
-  } else if (sret < 0) {
-
-    *buf = -1;
-    return 0;
-
-  }
-
-  ssize_t len_read = read(fd, ((u8 *)buf), len);
-  if (len_read < len) { return 0; }
+    if (likely(len_read == 4)) {  // for speed we put this first
 
 #if defined(__linux__)
-  u32 exec_ms =
-      MIN(timeout_ms,
+      u32 exec_ms = MIN(
+          timeout_ms,
           ((u64)timeout_ms - (timeout.tv_sec * 1000 + timeout.tv_usec / 1000)));
 #else
       u32 exec_ms = MIN(timeout_ms, get_cur_time_us() - read_start);
@@ -169,6 +163,32 @@ static u32 read_s32_timed(s32 fd, s32 *buf, u32 timeout_ms,
       // ensure to report 1 ms has passed (0 is an error)
       return exec_ms > 0 ? exec_ms : 1;
 
+    } else if (unlikely(len_read == -1 && errno == EINTR)) {
+
+      goto restart_read;
+
+    } else if (unlikely(len_read < 4)) {
+
+      return 0;
+
+    }
+
+  } else if (unlikely(!sret)) {
+
+    *buf = -1;
+    return timeout_ms + 1;
+
+  } else if (unlikely(sret < 0)) {
+
+    if (likely(errno == EINTR)) goto restart_select;
+
+    *buf = -1;
+    return 0;
+
+  }
+
+  return 0;  // not reached
+
 }
 
 /* Internal forkserver for non_instrumented_mode=1 and non-forkserver mode runs.