From a42aaad2e47b23d63037bfc0130e33fc0f74cd71 Mon Sep 17 00:00:00 2001 From: Ricardo Ribalda Date: Wed, 4 Jan 2023 15:38:48 +0100 Subject: kexec: introduce sysctl parameters kexec_load_limit_* kexec allows replacing the current kernel with a different one. This is usually a source of concerns for sysadmins that want to harden a system. Linux already provides a way to disable loading new kexec kernel via kexec_load_disabled, but that control is very coard, it is all or nothing and does not make distinction between a panic kexec and a normal kexec. This patch introduces new sysctl parameters, with finer tuning to specify how many times a kexec kernel can be loaded. The sysadmin can set different limits for kexec panic and kexec reboot kernels. The value can be modified at runtime via sysctl, but only with a stricter value. With these new parameters on place, a system with loadpin and verity enabled, using the following kernel parameters: sysctl.kexec_load_limit_reboot=0 sysct.kexec_load_limit_panic=1 can have a good warranty that if initrd tries to load a panic kernel, a malitious user will have small chances to replace that kernel with a different one, even if they can trigger timeouts on the disk where the panic kernel lives. Link: https://lkml.kernel.org/r/20221114-disable-kexec-reset-v6-3-6a8531a09b9a@chromium.org Signed-off-by: Ricardo Ribalda Reviewed-by: Steven Rostedt (Google) Acked-by: Baoquan He Cc: Bagas Sanjaya Cc: "Eric W. Biederman" Cc: Guilherme G. Piccoli # Steam Deck Cc: Joel Fernandes (Google) Cc: Jonathan Corbet Cc: Philipp Rudo Cc: Ross Zwisler Cc: Sergey Senozhatsky Signed-off-by: Andrew Morton --- include/linux/kexec.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'include/linux') diff --git a/include/linux/kexec.h b/include/linux/kexec.h index f18a3c9e813b..6883c5922701 100644 --- a/include/linux/kexec.h +++ b/include/linux/kexec.h @@ -404,7 +404,7 @@ extern int kimage_crash_copy_vmcoreinfo(struct kimage *image); extern struct kimage *kexec_image; extern struct kimage *kexec_crash_image; -bool kexec_load_permitted(void); +bool kexec_load_permitted(int kexec_image_type); #ifndef kexec_flush_icache_page #define kexec_flush_icache_page(page) -- cgit