[lxc-devel] [lxd/master] seccomp: protect against syscall supervision override

[brauner on Github]

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From 543f021101c6fe5aad6b2b0e207da0dac8167852 Mon Sep 17 00:00:00 2001
From: Christian Brauner <christian.brauner at ubuntu.com>
Date: Wed, 23 Oct 2019 01:00:46 +0200
Subject: [PATCH] seccomp: protect against syscall supervision override

Signed-off-by: Christian Brauner <christian.brauner at ubuntu.com>
---
 lxd/seccomp/seccomp.go | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/lxd/seccomp/seccomp.go b/lxd/seccomp/seccomp.go
index 9c00e2eaac..b194868e56 100644
--- a/lxd/seccomp/seccomp.go
+++ b/lxd/seccomp/seccomp.go
@@ -261,6 +261,9 @@ init_module errno 38
 finit_module errno 38
 delete_module errno 38
 `
+const seccompNotifyDisallow = `seccomp errno 22 [1,2146435072,SCMP_CMP_MASKED_EQ,2146435072]
+seccomp errno 22 [1,8,SCMP_CMP_MASKED_EQ,8]
+`
 
 const seccompNotifyMknod = `mknod notify [1,8192,SCMP_CMP_MASKED_EQ,61440]
 mknod notify [1,24576,SCMP_CMP_MASKED_EQ,61440]
@@ -447,6 +450,10 @@ func seccompGetPolicyContent(c Instance) (string, error) {
 		if shared.IsTrue(config["security.syscalls.intercept.setxattr"]) {
 			policy += seccompNotifySetxattr
 		}
+
+		// Prevent the container from overriding our syscall
+		// supervision.
+		policy += seccompNotifyDisallow
 	}
 
 	if whitelist != "" {