Bugfix: Check for readlink buffer overflow and handle gracefully

If readlink returns the size of the buffer, an overflow may have (safely) occurred.
Pass a buffer size of MAX_PATH+1 (the size of the actual buffer) to detect this scenario.

1 files changed, 3 insertions, 2 deletions

diff --git a/src/qt/guiutil.cpp b/src/qt/guiutil.cpp
index 558d4f108c..cb8be5b9ba 100644
--- a/src/qt/guiutil.cpp
+++ b/src/qt/guiutil.cpp
@@ -743,9 +743,10 @@ bool SetStartOnSystemStartup(bool fAutoStart)
     else
     {
         char pszExePath[MAX_PATH+1];
-        ssize_t r = readlink("/proc/self/exe", pszExePath, sizeof(pszExePath) - 1);
-        if (r == -1)
+        ssize_t r = readlink("/proc/self/exe", pszExePath, sizeof(pszExePath));
+        if (r == -1 || r > MAX_PATH) {
             return false;
+        }
         pszExePath[r] = '\0';
 
         fs::create_directories(GetAutostartDir());