Bug 1590984 - Use poll() instead of select() in WebRTC code r=drno

The use of select() was leading to crashes when the file descriptor value was
larger than FD_SETSIZE. Recent versions of glibc have checks in the FD_CLR(),
FD_SET() and FD_ISSET() macros that will abort() the program instead of doing
an out-of-bounds access. poll() doesn't have limitations on the file
descriptor values and provides behavior that is otherwise identical to
select() thus solving the problem.

Differential Revision: https://phabricator.services.mozilla.com/D50798

--HG--
extra : moz-landing-system : lando

media/webrtc/trunk/webrtc/modules/video_capture/linux/device_info_linux.cc

@@ -12,6 +12,7 @@
 
 #include <errno.h>
 #include <fcntl.h>
+#include <poll.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <sys/ioctl.h>
@@ -72,16 +73,13 @@ void DeviceInfoLinux::HandleEvent(inotify_event* event, int fd)
 
 int DeviceInfoLinux::EventCheck(int fd)
 {
-    struct timeval timeout;
-    fd_set rfds;
+    struct pollfd fds = {
+      .fd = fd,
+      .events = POLLIN,
+      .revents = 0
+    };
 
-    timeout.tv_sec = 0;
-    timeout.tv_usec = 100000;
-
-    FD_ZERO(&rfds);
-    FD_SET(fd, &rfds);
-
-    return select(fd+1, &rfds, NULL, NULL, &timeout);
+    return poll(&fds, 1, 100);
 }
 
 int DeviceInfoLinux::HandleEvents(int fd)

media/webrtc/trunk/webrtc/modules/video_capture/linux/video_capture_linux.cc

@@ -12,6 +12,7 @@
 
 #include <errno.h>
 #include <fcntl.h>
+#include <poll.h>
 #include <stdio.h>
 #include <string.h>
 #include <sys/ioctl.h>
@@ -370,25 +371,23 @@ bool VideoCaptureModuleV4L2::CaptureThread(void* obj) {
 }
 bool VideoCaptureModuleV4L2::CaptureProcess() {
   int retVal = 0;
-  fd_set rSet;
-  struct timeval timeout;
+  struct pollfd rSet;
 
   rtc::CritScope cs(&_captureCritSect);
 
-  FD_ZERO(&rSet);
-  FD_SET(_deviceFd, &rSet);
-  timeout.tv_sec = 1;
-  timeout.tv_usec = 0;
+  rSet.fd = _deviceFd;
+  rSet.events = POLLIN;
+  rSet.revents = 0;
 
-  retVal = select(_deviceFd + 1, &rSet, NULL, NULL, &timeout);
+  retVal = poll(&rSet, 1, 1000);
   if (retVal < 0 && errno != EINTR)  // continue if interrupted
   {
-    // select failed
+    // poll failed
     return false;
   } else if (retVal == 0) {
-    // select timed out
+    // poll timed out
     return true;
-  } else if (!FD_ISSET(_deviceFd, &rSet)) {
+  } else if (!(rSet.revents & POLLIN)) {
     // not event on camera handle
     return true;
   }