From d56e0e1e8e89a50d2a3fe53a29cde3aa91a93fcb Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Alexander=20Mei=C3=9Fner?= <AlexanderMeissner@gmx.net>
Date: Thu, 3 Aug 2023 19:18:25 +0200
Subject: [PATCH] Disables little-endian byte swap instructions in SBPFv2.
 (#493)

---
 src/elf.rs         |  5 +++++
 src/interpreter.rs |  2 +-
 src/jit.rs         |  2 +-
 src/verifier.rs    |  2 +-
 tests/execution.rs | 25 +++++++++++++++++--------
 5 files changed, 25 insertions(+), 11 deletions(-)

diff --git a/src/elf.rs b/src/elf.rs
index 8b17d1143..ce1218b0c 100644
--- a/src/elf.rs
+++ b/src/elf.rs
@@ -220,6 +220,11 @@ pub enum SBPFVersion {
 }
 
 impl SBPFVersion {
+    /// Enable the little-endian byte swap instructions
+    pub fn enable_le(&self) -> bool {
+        self == &SBPFVersion::V1
+    }
+
     /// Enable the negation instruction
     pub fn enable_neg(&self) -> bool {
         self == &SBPFVersion::V1
diff --git a/src/interpreter.rs b/src/interpreter.rs
index 218ab1b4b..7dd294eec 100644
--- a/src/interpreter.rs
+++ b/src/interpreter.rs
@@ -316,7 +316,7 @@ impl<'a, 'b, V: Verifier, C: ContextObject> Interpreter<'a, 'b, V, C> {
             ebpf::MOV32_REG  => self.reg[dst] = (self.reg[src] as u32) as u64,
             ebpf::ARSH32_IMM => self.reg[dst] = (self.reg[dst] as i32).wrapping_shr(insn.imm as u32)      as u64 & (u32::MAX as u64),
             ebpf::ARSH32_REG => self.reg[dst] = (self.reg[dst] as i32).wrapping_shr(self.reg[src] as u32) as u64 & (u32::MAX as u64),
-            ebpf::LE         => {
+            ebpf::LE if self.executable.get_sbpf_version().enable_le() => {
                 self.reg[dst] = match insn.imm {
                     16 => (self.reg[dst] as u16).to_le() as u64,
                     32 => (self.reg[dst] as u32).to_le() as u64,
diff --git a/src/jit.rs b/src/jit.rs
index a3d67142c..aeced76bf 100644
--- a/src/jit.rs
+++ b/src/jit.rs
@@ -523,7 +523,7 @@ impl<'a, V: Verifier, C: ContextObject> JitCompiler<'a, V, C> {
                 ebpf::MOV32_REG  => self.emit_ins(X86Instruction::mov(OperandSize::S32, src, dst)),
                 ebpf::ARSH32_IMM => self.emit_shift(OperandSize::S32, 7, R11, dst, Some(insn.imm)),
                 ebpf::ARSH32_REG => self.emit_shift(OperandSize::S32, 7, src, dst, None),
-                ebpf::LE         => {
+                ebpf::LE if self.executable.get_sbpf_version().enable_le() => {
                     match insn.imm {
                         16 => {
                             self.emit_ins(X86Instruction::alu(OperandSize::S32, 0x81, 4, dst, 0xffff, None)); // Mask to 16 bit
diff --git a/src/verifier.rs b/src/verifier.rs
index 06aec671b..db483568c 100644
--- a/src/verifier.rs
+++ b/src/verifier.rs
@@ -303,7 +303,7 @@ impl Verifier for RequisiteVerifier {
                 ebpf::MOV32_REG  => {},
                 ebpf::ARSH32_IMM => { check_imm_shift(&insn, insn_ptr, 32)?; },
                 ebpf::ARSH32_REG => {},
-                ebpf::LE         => { check_imm_endian(&insn, insn_ptr)?; },
+                ebpf::LE         if sbpf_version.enable_le() => { check_imm_endian(&insn, insn_ptr)?; },
                 ebpf::BE         => { check_imm_endian(&insn, insn_ptr)?; },
 
                 // BPF_ALU64 class
diff --git a/tests/execution.rs b/tests/execution.rs
index 1b2d83d40..816700783 100644
--- a/tests/execution.rs
+++ b/tests/execution.rs
@@ -649,25 +649,27 @@ fn test_be64() {
 
 #[test]
 fn test_le16() {
+    let config = Config {
+        enable_sbpf_v2: false,
+        ..Config::default()
+    };
     test_interpreter_and_jit_asm!(
         "
         ldxh r0, [r1]
         le16 r0
         exit",
+        config,
         [0x22, 0x11],
         (),
         TestContextObject::new(3),
         ProgramResult::Ok(0x1122),
     );
-}
-
-#[test]
-fn test_le16_high() {
     test_interpreter_and_jit_asm!(
         "
         ldxdw r0, [r1]
         le16 r0
         exit",
+        config,
         [0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77, 0x88],
         (),
         TestContextObject::new(3),
@@ -677,25 +679,27 @@ fn test_le16_high() {
 
 #[test]
 fn test_le32() {
+    let config = Config {
+        enable_sbpf_v2: false,
+        ..Config::default()
+    };
     test_interpreter_and_jit_asm!(
         "
         ldxw r0, [r1]
         le32 r0
         exit",
+        config,
         [0x44, 0x33, 0x22, 0x11],
         (),
         TestContextObject::new(3),
         ProgramResult::Ok(0x11223344),
     );
-}
-
-#[test]
-fn test_le32_high() {
     test_interpreter_and_jit_asm!(
         "
         ldxdw r0, [r1]
         le32 r0
         exit",
+        config,
         [0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77, 0x88],
         (),
         TestContextObject::new(3),
@@ -705,11 +709,16 @@ fn test_le32_high() {
 
 #[test]
 fn test_le64() {
+    let config = Config {
+        enable_sbpf_v2: false,
+        ..Config::default()
+    };
     test_interpreter_and_jit_asm!(
         "
         ldxdw r0, [r1]
         le64 r0
         exit",
+        config,
         [0x88, 0x77, 0x66, 0x55, 0x44, 0x33, 0x22, 0x11],
         (),
         TestContextObject::new(3),