From 4621cd674d0a95b08e2f9bf8a7b69f6990cf5f2b Mon Sep 17 00:00:00 2001
From: uuuvn <uuuvn@uuuvn.space>
Date: Thu, 4 May 2023 15:58:05 +0400
Subject: [PATCH] Fix kernel DoS via sigreturn from non-signal context

---
 src/syscall/process.rs | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/src/syscall/process.rs b/src/syscall/process.rs
index fb572096e8..f7b1186dc4 100644
--- a/src/syscall/process.rs
+++ b/src/syscall/process.rs
@@ -381,8 +381,12 @@ pub fn sigreturn() -> Result<usize> {
         let contexts = context::contexts();
         let context_lock = contexts.current().ok_or(Error::new(ESRCH))?;
         let mut context = context_lock.write();
-        context.ksig_restore = true;
-        context.block("sigreturn");
+        if context.ksig.is_some() {
+            context.ksig_restore = true;
+            context.block("sigreturn");
+        } else {
+            return Err(Error::new(EINVAL));
+        }
     }
 
     let _ = unsafe { context::switch() };