linux-kernel - [PATCH 12/12] kexec: Require CAP_SYS_COMPROMISE

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Message-Id: <1363642353-30749-12-git-send-email-matthew.garrett@nebula.com>
Date:	Mon, 18 Mar 2013 17:32:33 -0400
From:	Matthew Garrett <matthew.garrett@...ula.com>
To:	linux-kernel@...r.kernel.org
Cc:	linux-security-module@...r.kernel.org, linux-efi@...r.kernel.org,
	kexec@...ts.infradead.org, linux-pci@...r.kernel.org,
	Matthew Garrett <matthew.garrett@...ula.com>
Subject: [PATCH 12/12] kexec: Require CAP_SYS_COMPROMISE_KERNEL

kexec can easily be used to modify the security policy of a running kernel.
CONFIG_KEXEC_JUMP makes it trivial for an attacker to simply jump to another
kernel, modify the security policy of the previous kernel and then switch
back, but it's still merely a matter of difficulty. Long term we'll want
an interface for ensuring that kexec is able to launch signed code, but we
should default to safe behaviour for now.

Signed-off-by: Matthew Garrett <matthew.garrett@...ula.com>
---
 kernel/kexec.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/kexec.c b/kernel/kexec.c
index bddd3d7..cbdb930 100644
--- a/kernel/kexec.c
+++ b/kernel/kexec.c
@@ -946,7 +946,7 @@ SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned long, nr_segments,
 	int result;
 
 	/* We only trust the superuser with rebooting the system. */
-	if (!capable(CAP_SYS_BOOT))
+	if (!capable(CAP_SYS_BOOT) || !capable(CAP_COMPROMISE_KERNEL))
 		return -EPERM;
 
 	/*
-- 
1.8.1.2

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