From ee338b9ee2822e65a85750da6129946c14962410 Mon Sep 17 00:00:00 2001 From: Baoquan He Date: Fri, 24 May 2019 15:38:09 +0800 Subject: [PATCH] x86/kexec/64: Prevent kexec from 5-level paging to a 4-level only kernel If the running kernel has 5-level paging activated, the 5-level paging mode is preserved across kexec. If the kexec'ed kernel does not contain support for handling active 5-level paging mode in the decompressor, the decompressor will crash with #GP. Prevent this situation at load time. If 5-level paging is active, check the xloadflags whether the kexec kernel can handle 5-level paging at least in the decompressor. If not, reject the load attempt and print out an error message. Signed-off-by: Baoquan He Signed-off-by: Thomas Gleixner Acked-by: Kirill A. Shutemov Cc: bp@alien8.de Cc: hpa@zytor.com Cc: dyoung@redhat.com Link: https://lkml.kernel.org/r/20190524073810.24298-3-bhe@redhat.com --- arch/x86/kernel/kexec-bzimage64.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/arch/x86/kernel/kexec-bzimage64.c b/arch/x86/kernel/kexec-bzimage64.c index 22f60dd..7f43973 100644 --- a/arch/x86/kernel/kexec-bzimage64.c +++ b/arch/x86/kernel/kexec-bzimage64.c @@ -321,6 +321,11 @@ static int bzImage64_probe(const char *buf, unsigned long len) return ret; } + if (!(header->xloadflags & XLF_5LEVEL) && pgtable_l5_enabled()) { + pr_err("bzImage cannot handle 5-level paging mode.\n"); + return ret; + } + /* I've got a bzImage */ pr_debug("It's a relocatable bzImage64\n"); ret = 0; -- 2.7.4