From ac9c5d0ba4ad5ae07617a1040b18aad47c4789c4 Mon Sep 17 00:00:00 2001
From: SREsAreHumanToo <88474954+sresarehumantoo@users.noreply.github.com>
Date: Mon, 7 Sep 2026 22:37:00 -0400
Subject: [PATCH] fix(linux): guard XRandR NULL returns to avoid a SEGV during
 display setup

XRRGetScreenResources and XRRGetCrtcInfo both return NULL on a transient X
error, which happens while the RandR configuration is still settling (for
example when a second CRTC is being brought up as a multi-display session
starts). Three call sites dereference the result without checking it, so the
whole process dies instead of reporting a failure the caller can retry.

Check all three: both x11_attr_t::init() and x11_display_names() bail out the
way the adjacent xdisplay failures already do, and the CRTC lookup falls
through to the existing "record the entire virtual desktop" path.

Observed on a two-display session that raced CRTC bring-up, where sunshine
would SEGV on session start and succeed on retry.
---
 src/platform/linux/x11grab.cpp | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/src/platform/linux/x11grab.cpp b/src/platform/linux/x11grab.cpp
index a14b3b66d09..57d57fda98c 100644
--- a/src/platform/linux/x11grab.cpp
+++ b/src/platform/linux/x11grab.cpp
@@ -513,6 +513,10 @@ namespace platf {
       }
 
       screen_res_t screenr {x11::rr::GetScreenResources(xdisplay.get(), xwindow)};
+      if (!screenr) {
+        BOOST_LOG(error) << "Could not query X screen resources"sv;
+        return -1;
+      }
       int output = screenr->noutput;
 
       output_info_t result;
@@ -531,8 +535,12 @@ namespace platf {
         }
       }
 
+      crtc_info_t crt_info;
       if (result_found && result->crtc) {
-        crtc_info_t crt_info {x11::rr::GetCrtcInfo(xdisplay.get(), screenr.get(), result->crtc)};
+        crt_info = crtc_info_t {x11::rr::GetCrtcInfo(xdisplay.get(), screenr.get(), result->crtc)};
+      }
+
+      if (crt_info) {
         BOOST_LOG(info)
           << "Streaming display: "sv << result->name << " with res "sv << crt_info->width << 'x' << crt_info->height << " offset by "sv << crt_info->x << 'x' << crt_info->y;
 
@@ -942,6 +950,10 @@ namespace platf {
 
     auto xwindow = DefaultRootWindow(xdisplay.get());
     screen_res_t screenr {x11::rr::GetScreenResources(xdisplay.get(), xwindow)};
+    if (!screenr) {
+      BOOST_LOG(error) << "Could not query X screen resources"sv;
+      return {};
+    }
     int output = screenr->noutput;
 
     std::vector<std::string> names;