From c8eea7d45b0a374a660275145b546a656e269906 Mon Sep 17 00:00:00 2001
From: Mathieu Strypsteen <mathieu@strypsteen.me>
Date: Sun, 29 Dec 2024 11:31:42 +0100
Subject: [PATCH] Require unused syscall args to be zero

---
 Cargo.lock                | 14 +++++------
 kernel/src/sys/syscall.rs | 52 +++++++++++++++++++++++++++++++++------
 2 files changed, 51 insertions(+), 15 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index d42db4c..8fe5567 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -70,7 +70,7 @@ dependencies = [
  "regex",
  "rustc-hash",
  "shlex",
- "syn 2.0.92",
+ "syn 2.0.93",
 ]
 
 [[package]]
@@ -205,9 +205,9 @@ checksum = "e6d5a32815ae3f33302d95fdcb2ce17862f8c65363dcfd29360480ba1001fc9c"
 
 [[package]]
 name = "glob"
-version = "0.3.1"
+version = "0.3.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d2fabcfbdc87f4758337ca535fb41a6d701b65693ce38287d856d1674551ec9b"
+checksum = "a8d1add55171497b4705a648c6b583acafb01d58050a51727785f0b2c8e0a2b2"
 
 [[package]]
 name = "hashbrown"
@@ -347,7 +347,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "64d1ec885c64d0457d564db4ec299b2dae3f9c02808b8ad9c3a089c591b18033"
 dependencies = [
  "proc-macro2",
- "syn 2.0.92",
+ "syn 2.0.93",
 ]
 
 [[package]]
@@ -472,9 +472,9 @@ dependencies = [
 
 [[package]]
 name = "syn"
-version = "2.0.92"
+version = "2.0.93"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "70ae51629bf965c5c098cc9e87908a3df5301051a9e087d6f9bef5c9771ed126"
+checksum = "9c786062daee0d6db1132800e623df74274a0a87322d8e183338e01b3d98d058"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -520,7 +520,7 @@ checksum = "9b24e77d3fc1e617051e630f99da24bcae6328abab37b8f9216bb68d06804f9a"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.92",
+ "syn 2.0.93",
 ]
 
 [[package]]
diff --git a/kernel/src/sys/syscall.rs b/kernel/src/sys/syscall.rs
index 2ef6e71..45aeb53 100644
--- a/kernel/src/sys/syscall.rs
+++ b/kernel/src/sys/syscall.rs
@@ -16,12 +16,27 @@ use super::{
 struct SyscallArgs {
     arg1: usize,
     arg2: usize,
-    _arg3: usize,
-    _arg4: usize,
-    _arg5: usize,
+    arg3: usize,
+    arg4: usize,
+    arg5: usize,
+}
+struct Syscall {
+    func: fn(SyscallArgs) -> Result<usize, Box<dyn Error>>,
+    num_args: usize,
 }
 
-const SYSCALL_TABLE: [fn(SyscallArgs) -> Result<usize, Box<dyn Error>>; 4] = [syscall_get_kernel_version, syscall_exit, syscall_debug_print, syscall_get_pid];
+const SYSCALL_TABLE: [Syscall; 4] = [
+    Syscall {
+        func: syscall_get_kernel_version,
+        num_args: 0,
+    },
+    Syscall { func: syscall_exit, num_args: 1 },
+    Syscall {
+        func: syscall_debug_print,
+        num_args: 2,
+    },
+    Syscall { func: syscall_get_pid, num_args: 0 },
+];
 
 fn copy_from_user(start: u64, size: usize) -> Result<Vec<u8>, Box<dyn Error>> {
     if size > 16 * 1024 * 1024 {
@@ -78,11 +93,32 @@ extern "C" fn syscall_handler(syscall: u64, arg1: u64, arg2: u64, arg3: u64, arg
     let args = SyscallArgs {
         arg1: arg1 as usize,
         arg2: arg2 as usize,
-        _arg3: arg3 as usize,
-        _arg4: arg4 as usize,
-        _arg5: arg5 as usize,
+        arg3: arg3 as usize,
+        arg4: arg4 as usize,
+        arg5: arg5 as usize,
     };
-    let result = SYSCALL_TABLE[syscall as usize](args);
+    let syscall = &SYSCALL_TABLE[syscall as usize];
+    let mut error = false;
+    if syscall.num_args < 5 && args.arg5 != 0 {
+        error = true;
+    }
+    if syscall.num_args < 4 && args.arg4 != 0 {
+        error = true;
+    }
+    if syscall.num_args < 3 && args.arg3 != 0 {
+        error = true;
+    }
+    if syscall.num_args < 2 && args.arg2 != 0 {
+        error = true;
+    }
+    if syscall.num_args < 1 && args.arg1 != 0 {
+        error = true;
+    }
+    if error {
+        debug!("Process passed invalid syscall arguments");
+        terminate_current_task();
+    }
+    let result = (syscall.func)(args);
     if result.is_err() {
         debug!("Error during syscall: {}", result.err().unwrap());
         terminate_current_task();