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From: Kristen Carlson Accardi <kristen@linux.intel.com>
To: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de,
	hpa@zytor.com, arjan@linux.intel.com, keescook@chromium.org
Cc: rick.p.edgecombe@intel.com, x86@kernel.org,
	linux-kernel@vger.kernel.org,
	kernel-hardening@lists.openwall.com,
	Kristen Carlson Accardi <kristen@linux.intel.com>
Subject: [RFC PATCH 09/11] kallsyms: hide layout and expose seed
Date: Wed,  5 Feb 2020 14:39:48 -0800
Message-ID: <20200205223950.1212394-10-kristen@linux.intel.com> (raw)
In-Reply-To: <20200205223950.1212394-1-kristen@linux.intel.com>

To support finer grained kaslr (fgkaslr), we need to make a couple changes
to kallsyms. Firstly, we need to hide our sorted list of symbols, since
this will give away our new layout. Secondly, we will export the seed used
for randomizing the layout so that it can be used to make a particular
layout persist across boots for debug purposes.

Signed-off-by: Kristen Carlson Accardi <kristen@linux.intel.com>
---
 kernel/kallsyms.c | 30 +++++++++++++++++++++++++++++-
 1 file changed, 29 insertions(+), 1 deletion(-)

diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
index 136ce049c4ad..432b13a3a033 100644
--- a/kernel/kallsyms.c
+++ b/kernel/kallsyms.c
@@ -698,6 +698,21 @@ const char *kdb_walk_kallsyms(loff_t *pos)
 }
 #endif	/* CONFIG_KGDB_KDB */
 
+#ifdef CONFIG_FG_KASLR
+extern const u64 fgkaslr_seed[] __weak;
+
+static int proc_fgkaslr_show(struct seq_file *m, void *v)
+{
+	seq_printf(m, "%llx\n", fgkaslr_seed[0]);
+	seq_printf(m, "%llx\n", fgkaslr_seed[1]);
+	seq_printf(m, "%llx\n", fgkaslr_seed[2]);
+	seq_printf(m, "%llx\n", fgkaslr_seed[3]);
+	return 0;
+}
+#else
+static inline int proc_fgkaslr_show(struct seq_file *m, void *v) { return 0; }
+#endif
+
 static const struct file_operations kallsyms_operations = {
 	.open = kallsyms_open,
 	.read = seq_read,
@@ -707,7 +722,20 @@ static const struct file_operations kallsyms_operations = {
 
 static int __init kallsyms_init(void)
 {
-	proc_create("kallsyms", 0444, NULL, &kallsyms_operations);
+	/*
+	 * When fine grained kaslr is enabled, we don't want to
+	 * print out the symbols even with zero pointers because
+	 * this reveals the randomization order. If fg kaslr is
+	 * enabled, make kallsyms available only to privileged
+	 * users.
+	 */
+	if (!IS_ENABLED(CONFIG_FG_KASLR))
+		proc_create("kallsyms", 0444, NULL, &kallsyms_operations);
+	else {
+		proc_create_single("fgkaslr_seed", 0400, NULL,
+					proc_fgkaslr_show);
+		proc_create("kallsyms", 0400, NULL, &kallsyms_operations);
+	}
 	return 0;
 }
 device_initcall(kallsyms_init);
-- 
2.24.1


  parent reply index

Thread overview: 73+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-05 22:39 [RFC PATCH 00/11] Finer grained kernel address space randomization Kristen Carlson Accardi
2020-02-05 22:39 ` [RFC PATCH 01/11] modpost: Support >64K sections Kristen Carlson Accardi
2020-02-06 12:38   ` Kees Cook
2020-02-05 22:39 ` [RFC PATCH 02/11] x86: tools/relocs: Support >64K section headers Kristen Carlson Accardi
2020-02-06 12:39   ` Kees Cook
2020-02-05 22:39 ` [RFC PATCH 03/11] x86/boot: Allow a "silent" kaslr random byte fetch Kristen Carlson Accardi
2020-02-06  1:08   ` Andy Lutomirski
2020-02-06 11:48     ` Kees Cook
2020-02-06 16:58     ` Kristen Carlson Accardi
2020-02-05 22:39 ` [RFC PATCH 04/11] x86/boot/KASLR: Introduce PRNG for faster shuffling Kristen Carlson Accardi
2020-02-06  1:11   ` Andy Lutomirski
2020-02-06 15:10   ` Jason A. Donenfeld
2020-02-07  7:23     ` Jean-Philippe Aumasson
2020-02-07  9:05       ` Kees Cook
2020-02-07 16:52         ` Kristen Carlson Accardi
2020-02-05 22:39 ` [RFC PATCH 05/11] x86: Makefile: Add build and config option for CONFIG_FG_KASLR Kristen Carlson Accardi
2020-02-06 10:30   ` Peter Zijlstra
2020-02-06 11:52     ` Kees Cook
2020-02-25 17:55   ` Arvind Sankar
2020-02-26 19:13     ` Kristen Carlson Accardi
2020-03-24 21:24     ` Kristen Carlson Accardi
2020-03-25 15:34       ` Kees Cook
2020-02-05 22:39 ` [RFC PATCH 06/11] x86: make sure _etext includes function sections Kristen Carlson Accardi
2020-02-06 12:26   ` Kees Cook
2020-02-06 13:15     ` Jann Horn
2020-02-06 16:27       ` David Laight
2020-02-06 14:39     ` Arvind Sankar
2020-02-06 15:29       ` Arvind Sankar
2020-02-06 16:11         ` Andy Lutomirski
2020-02-06 14:57     ` Arvind Sankar
2020-02-06 15:45       ` Arvind Sankar
2020-02-06 19:41     ` Kristen Carlson Accardi
2020-02-06 20:02       ` Andy Lutomirski
2020-02-07  9:24         ` Peter Zijlstra
2020-02-10  1:43           ` Kees Cook
2020-02-10 10:51             ` Peter Zijlstra
2020-02-10 15:54               ` Arjan van de Ven
2020-02-10 16:36                 ` Arvind Sankar
2020-02-21 19:50                   ` Josh Poimboeuf
2020-02-21 23:05                     ` Arvind Sankar
2020-02-05 22:39 ` [RFC PATCH 07/11] x86/tools: Adding relative relocs for randomized functions Kristen Carlson Accardi
2020-02-06 12:37   ` Kees Cook
2020-02-05 22:39 ` [RFC PATCH 08/11] x86: Add support for finer grained KASLR Kristen Carlson Accardi
2020-02-06  1:17   ` Andy Lutomirski
2020-02-06 11:56     ` Kees Cook
2020-02-06 17:36       ` Kristen Carlson Accardi
2020-02-06 10:38   ` Peter Zijlstra
2020-02-06 12:06     ` Kees Cook
2020-02-06 14:52       ` Peter Zijlstra
2020-02-06 17:25         ` Kristen Carlson Accardi
2020-02-06 17:35           ` Peter Zijlstra
2020-02-06 17:43             ` Kristen Carlson Accardi
2020-02-25 17:49   ` Arvind Sankar
2020-02-26 19:26     ` Kristen Carlson Accardi
2020-02-05 22:39 ` Kristen Carlson Accardi [this message]
2020-02-06 12:32   ` [RFC PATCH 09/11] kallsyms: hide layout and expose seed Kees Cook
2020-02-06 17:51     ` Kristen Carlson Accardi
2020-02-06 19:27       ` Jann Horn
2020-03-02 19:01         ` Kristen Carlson Accardi
2020-03-02 19:08           ` Kees Cook
2020-03-02 19:19             ` Kristen Carlson Accardi
2020-02-27  2:42       ` Baoquan He
2020-02-27 16:02         ` Kees Cook
2020-02-28  3:36           ` Baoquan He
2020-02-05 22:39 ` [RFC PATCH 10/11] module: Reorder functions Kristen Carlson Accardi
2020-02-06 12:41   ` Kees Cook
2020-02-11 12:39     ` Jessica Yu
2020-02-05 22:39 ` [RFC PATCH 11/11] x86/boot: Move "boot heap" out of .bss Kristen Carlson Accardi
2020-02-06  0:11   ` Arvind Sankar
2020-02-06  0:33     ` Kristen Carlson Accardi
2020-02-06 11:13     ` Kees Cook
2020-02-06 14:25       ` Arvind Sankar
2020-02-06 21:32         ` Kees Cook

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