From 1bcf116859fd2a0f04c18bdc8ff9c2038f5f0e40 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Daniel=20Ekl=C3=B6f?= <daniel@ekloef.se>
Date: Thu, 30 Sep 2021 09:52:25 +0200
Subject: [PATCH] modules: handle udev_monitor_receive_device() returning NULL

Closes #109
---
 CHANGELOG.md         | 3 +++
 modules/backlight.c  | 6 ++++--
 modules/battery.c    | 4 +++-
 modules/removables.c | 3 +++
 4 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9f06a69..938c91e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -25,6 +25,9 @@
 
 * `left-margin` and `right-margin` from being rejected as invalid
   options.
+* Crash when `udev_monitor_receive_device()` returned `NULL`. This
+  affected the “backlight”, “battery” and “removables” modules
+  (https://codeberg.org/dnkl/yambar/issues/109).
 
 
 ### Security
diff --git a/modules/backlight.c b/modules/backlight.c
index e7bca2e..292b067 100644
--- a/modules/backlight.c
+++ b/modules/backlight.c
@@ -189,9 +189,11 @@ run(struct module *mod)
             break;
 
         struct udev_device *dev = udev_monitor_receive_device(mon);
-        const char *sysname = udev_device_get_sysname(dev);
+        if (dev == NULL)
+            continue;
 
-        bool is_us = strcmp(sysname, m->device) == 0;
+        const char *sysname = udev_device_get_sysname(dev);
+        bool is_us = sysname != NULL && strcmp(sysname, m->device) == 0;
         udev_device_unref(dev);
 
         if (!is_us)
diff --git a/modules/battery.c b/modules/battery.c
index 215fa32..4f17de4 100644
--- a/modules/battery.c
+++ b/modules/battery.c
@@ -437,8 +437,10 @@ run(struct module *mod)
 
         if (fds[1].revents & POLLIN) {
             struct udev_device *dev = udev_monitor_receive_device(mon);
-            const char *sysname = udev_device_get_sysname(dev);
+            if (dev == NULL)
+                continue;
 
+            const char *sysname = udev_device_get_sysname(dev);
             bool is_us = sysname != NULL && strcmp(sysname, m->battery) == 0;
             udev_device_unref(dev);
 
diff --git a/modules/removables.c b/modules/removables.c
index a676ceb..04d2695 100644
--- a/modules/removables.c
+++ b/modules/removables.c
@@ -571,6 +571,9 @@ run(struct module *mod)
 
         if (fds[1].revents & POLLIN) {
             struct udev_device *dev = udev_monitor_receive_device(dev_mon);
+            if (dev == NULL)
+                continue;
+
             if (handle_udev_event(mod, dev))
                 update = true;
             udev_device_unref(dev);