From: Matthew Garrett Date: Wed, 5 Apr 2017 17:40:30 +0100 Subject: [44/61] kexec: Disable at runtime if the kernel is locked down Origin: https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/commit?id=e7c340d3a52b23631aa5e67cd10eac766042db50 kexec permits the loading and execution of arbitrary code in ring 0, which is something that lock-down is meant to prevent. It makes sense to disable kexec in this situation. This does not affect kexec_file_load() which can check for a signature on the image to be booted. Signed-off-by: Matthew Garrett Signed-off-by: David Howells --- kernel/kexec.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/kernel/kexec.c b/kernel/kexec.c index 980936a90ee6..46de8e6b42f4 100644 --- a/kernel/kexec.c +++ b/kernel/kexec.c @@ -194,6 +194,13 @@ SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned long, nr_segments, return -EPERM; /* + * kexec can be used to circumvent module loading restrictions, so + * prevent loading in that case + */ + if (kernel_is_locked_down()) + return -EPERM; + + /* * Verify we have a legal set of flags * This leaves us room for future extensions. */