fix: preserve fixed metadata state when set_program fails

src/lib.rs

@@ -871,10 +871,10 @@ impl<'a> EbpfVmFixedMbuff<'a> {
     ) -> Result<(), Error> {
         let get_buff_len = |x: usize, y: usize| if x >= y { x + 8 } else { y + 8 };
         let buffer = vec![0u8; get_buff_len(data_offset, data_end_offset)];
+        self.parent.set_program(prog)?;
         self.mbuff.buffer = buffer;
         self.mbuff.data_offset = data_offset;
         self.mbuff.data_end_offset = data_end_offset;
-        self.parent.set_program(prog)?;
         Ok(())
     }
 

tests/misc.rs

@@ -695,6 +695,41 @@ fn test_verifier_fail() {
     assert_eq!(vm.execute_program().unwrap(), 0xBEE);
 }
 
+#[test]
+fn test_vm_fixed_mbuff_failed_set_program() {
+    let prog = assemble(
+        "ldxdw r0, [r1+16]
+         ldxdw r2, [r1+8]
+         sub64 r0, r2
+         exit",
+    )
+    .unwrap();
+    let replacement = assemble("exit").unwrap();
+
+    for custom_verifier in [false, true] {
+        let mut before = [1, 2, 3];
+        let mut after = [1, 2, 3];
+        let mut vm = rbpf::EbpfVmFixedMbuff::new(Some(&prog), 8, 16).unwrap();
+        assert_eq!(vm.execute_program(&mut before).unwrap(), 3);
+
+        let rejected = if custom_verifier {
+            vm.set_verifier(|prog| {
+                if prog.len() == rbpf::ebpf::INSN_SIZE {
+                    Err(Error::other("Rejected replacement program"))
+                } else {
+                    Ok(())
+                }
+            })
+            .unwrap();
+            replacement.as_slice()
+        } else {
+            &[]
+        };
+        assert!(vm.set_program(rejected, 0, 24).is_err());
+        assert_eq!(vm.execute_program(&mut after).unwrap(), 3);
+    }
+}
+
 #[test]
 fn test_vm_bpf_to_bpf_call() {
     let test_code = assemble(