From 4e04c396095b7e4b70f0635ded6241a61a62ada8 Mon Sep 17 00:00:00 2001
From: Matthias Clasen <mclasen@redhat.com>
Date: Thu, 15 Oct 2020 15:16:06 -0400
Subject: [PATCH] emojicompletion: Avoid a memory overrun

Don't read beyond the beginning of the string.

Fixes: #3245
---
 gtk/gtkemojicompletion.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/gtk/gtkemojicompletion.c b/gtk/gtkemojicompletion.c
index 712418850a..31669c85d5 100644
--- a/gtk/gtkemojicompletion.c
+++ b/gtk/gtkemojicompletion.c
@@ -115,7 +115,8 @@ next:
               break;
             }
         }
-      while (g_unichar_isalnum (g_utf8_get_char (p)) || *p == '_' || *p == ' ');
+      while (p > text &&
+             (g_unichar_isalnum (g_utf8_get_char (p)) || *p == '_' || *p == ' '));
 
       if (found_candidate)
         n_matches = populate_completion (completion, p, 0);