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

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Message-Id: <20200226215039.2842351-1-nivedita@alum.mit.edu>
Date:   Wed, 26 Feb 2020 16:50:39 -0500
From:   Arvind Sankar <nivedita@...m.mit.edu>
To:     "Tobin C . Harding" <me@...in.cc>, Tycho Andersen <tycho@...ho.ws>
Cc:     kernel-hardening@...ts.openwall.com,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] x86/mm/init_32: Don't print out kernel memory layout if KASLR

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

Signed-off-by: Arvind Sankar <nivedita@...m.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