reject overlapping media and database paths

src/config.rs

@@ -538,5 +538,27 @@ where
         return Err(Error::RegistrationTokenEmpty);
     }
 
+    match &config.media.backend {
+        MediaBackendConfig::Filesystem(x) => {
+            let media_path = x
+                .path
+                .canonicalize()
+                .map_err(|e| Error::Canonicalize(e, x.path.clone()))?;
+
+            let database_path =
+                config.database.path.canonicalize().map_err(|e| {
+                    Error::Canonicalize(e, config.database.path.clone())
+                })?;
+
+            let overlap = media_path == database_path
+                || media_path.starts_with(&database_path)
+                || database_path.starts_with(&media_path);
+
+            if overlap {
+                return Err(Error::DatabaseMediaOverlap);
+            }
+        }
+    }
+
     Ok(config)
 }

src/error.rs

@@ -134,8 +134,14 @@ pub(crate) enum Config {
     #[error("failed to parse configuration file {1:?}")]
     Parse(#[source] toml::de::Error, PathBuf),
 
+    #[error("failed to canonicalize path {}", .1.display())]
+    Canonicalize(#[source] std::io::Error, PathBuf),
+
     #[error("registration token must not be empty")]
     RegistrationTokenEmpty,
+
+    #[error("database and media paths overlap")]
+    DatabaseMediaOverlap,
 }
 
 /// Errors that can occur while searching for a config file