[PATCH] x86/mm/init_32: Don't print out kernel memory layout if KASLR

From: Arvind Sankar <nivedita@alum.mit.edu>
To: "Tobin C . Harding" <me@tobin.cc>, Tycho Andersen <tycho@tycho.ws>
Cc: kernel-hardening@lists.openwall.com,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Andy Lutomirski <luto@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	x86@kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH] x86/mm/init_32: Don't print out kernel memory layout if KASLR
Date: Wed, 26 Feb 2020 16:50:39 -0500	[thread overview]
Message-ID: <20200226215039.2842351-1-nivedita@alum.mit.edu> (raw)

For security, only show the virtual kernel memory layout if KASLR is
disabled.

Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
---
 arch/x86/mm/init_32.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/x86/mm/init_32.c b/arch/x86/mm/init_32.c
index 23df4885bbed..53635be69102 100644
--- a/arch/x86/mm/init_32.c
+++ b/arch/x86/mm/init_32.c
@@ -788,6 +788,10 @@ void __init mem_init(void)
 	x86_init.hyper.init_after_bootmem();
 
 	mem_init_print_info(NULL);
+
+	if (kaslr_enabled())
+		goto skip_layout;
+
 	printk(KERN_INFO "virtual kernel memory layout:\n"
 		"    fixmap  : 0x%08lx - 0x%08lx   (%4ld kB)\n"
 		"  cpu_entry : 0x%08lx - 0x%08lx   (%4ld kB)\n"
@@ -827,6 +831,7 @@ void __init mem_init(void)
 		(unsigned long)&_text, (unsigned long)&_etext,
 		((unsigned long)&_etext - (unsigned long)&_text) >> 10);
 
+skip_layout:
 	/*
 	 * Check boundaries twice: Some fundamental inconsistencies can
 	 * be detected at build time already.
-- 
2.24.1

