fix(#4886) more: panics if file is not readable

src/uu/more/src/more.rs

@@ -104,7 +104,17 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
             if length > 1 {
                 buff.push_str(&MULTI_FILE_TOP_PROMPT.replace("{}", file.to_str().unwrap()));
             }
-            let mut reader = BufReader::new(File::open(file).unwrap());
+            let opened_file = match File::open(file) {
+                Err(why) => {
+                    terminal::disable_raw_mode().unwrap();
+                    return Err(USimpleError::new(
+                        1,
+                        format!("cannot open {}: {}", file.quote(), why.kind()),
+                    ));
+                }
+                Ok(opened_file) => opened_file,
+            };
+            let mut reader = BufReader::new(opened_file);
             reader.read_to_string(&mut buff).unwrap();
             more(&buff, &mut stdout, next_file.copied(), &options)?;
             buff.clear();

tests/by-util/test_more.rs

@@ -1,6 +1,12 @@
 use crate::common::util::TestScenario;
 use is_terminal::IsTerminal;
 
+//Both following includes are only needed inside the test_more_invalid_file_perms()
+#[cfg(target_family = "unix")]
+use std::fs::{set_permissions, Permissions};
+#[cfg(target_family = "unix")]
+use std::os::unix::fs::PermissionsExt;
+
 #[test]
 fn test_more_no_arg() {
     // Reading from stdin is now supported, so this must succeed
@@ -32,3 +38,15 @@ fn test_more_dir_arg() {
             .usage_error("'.' is a directory.");
     }
 }
+
+#[test]
+#[cfg(target_family = "unix")]
+fn test_more_invalid_file_perms() {
+    if std::io::stdout().is_terminal() {
+        let (at, mut ucmd) = at_and_ucmd!();
+        let permissions = Permissions::from_mode(0o244);
+        at.make_file("invalid-perms.txt");
+        set_permissions(at.plus("invalid-perms.txt"), permissions).unwrap();
+        ucmd.arg("invalid-perms.txt").fails();
+    }
+}