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 10/11] module: Reorder functions
Date: Wed, 5 Feb 2020 14:39:49 -0800 [thread overview]
Message-ID: <20200205223950.1212394-11-kristen@linux.intel.com> (raw)
In-Reply-To: <20200205223950.1212394-1-kristen@linux.intel.com>
If a module has functions split out into separate text sections
(i.e. compiled with the -ffunction-sections flag), reorder the
functions to provide some code diversification to modules.
Signed-off-by: Kristen Carlson Accardi <kristen@linux.intel.com>
---
kernel/module.c | 85 +++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 85 insertions(+)
diff --git a/kernel/module.c b/kernel/module.c
index b56f3224b161..231563e95e61 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -53,6 +53,8 @@
#include <linux/bsearch.h>
#include <linux/dynamic_debug.h>
#include <linux/audit.h>
+#include <linux/random.h>
+#include <asm/setup.h>
#include <uapi/linux/module.h>
#include "module-internal.h"
@@ -3245,6 +3247,87 @@ static int find_module_sections(struct module *mod, struct load_info *info)
return 0;
}
+/*
+ * shuffle_text_list()
+ * Use a Fisher Yates algorithm to shuffle a list of text sections.
+ */
+static void shuffle_text_list(Elf_Shdr **list, int size)
+{
+ int i;
+ unsigned int j;
+ Elf_Shdr *temp;
+
+ for (i = size - 1; i > 0; i--) {
+ /*
+ * TBD - seed. We need to be able to use a known
+ * seed so that we can non-randomly randomize for
+ * debugging.
+ */
+
+ // pick a random index from 0 to i
+ get_random_bytes(&j, sizeof(j));
+ j = j % (i + 1);
+
+ temp = list[i];
+ list[i] = list[j];
+ list[j] = temp;
+ }
+}
+
+/*
+ * randomize_text()
+ * Look through the core section looking for executable code sections.
+ * Store sections in an array and then shuffle the sections
+ * to reorder the functions.
+ */
+static void randomize_text(struct module *mod, struct load_info *info)
+{
+ int i;
+ int num_text_sections = 0;
+ Elf_Shdr **text_list;
+ int size = 0;
+ int max_sections = info->hdr->e_shnum;
+ unsigned int sec = find_sec(info, ".text");
+
+ if (!IS_ENABLED(CONFIG_FG_KASLR) || !kaslr_enabled())
+ return;
+
+ if (sec == 0)
+ return;
+
+ text_list = kmalloc_array(max_sections, sizeof(*text_list), GFP_KERNEL);
+ if (text_list == NULL)
+ return;
+
+ for (i = 0; i < max_sections; i++) {
+ Elf_Shdr *shdr = &info->sechdrs[i];
+ const char *sname = info->secstrings + shdr->sh_name;
+
+ if (!(shdr->sh_flags & SHF_ALLOC) ||
+ !(shdr->sh_flags & SHF_EXECINSTR) ||
+ strstarts(sname, ".init"))
+ continue;
+
+ text_list[num_text_sections] = shdr;
+ num_text_sections++;
+ }
+
+ shuffle_text_list(text_list, num_text_sections);
+
+ for (i = 0; i < num_text_sections; i++) {
+ Elf_Shdr *shdr = text_list[i];
+ unsigned int infosec;
+ const char *sname;
+
+ sname = info->secstrings + shdr->sh_name;
+ infosec = shdr->sh_info;
+
+ shdr->sh_entsize = get_offset(mod, &size, shdr, infosec);
+ }
+
+ kfree(text_list);
+}
+
static int move_module(struct module *mod, struct load_info *info)
{
int i;
@@ -3282,6 +3365,8 @@ static int move_module(struct module *mod, struct load_info *info)
} else
mod->init_layout.base = NULL;
+ randomize_text(mod, info);
+
/* Transfer each section which specifies SHF_ALLOC */
pr_debug("final section addresses:\n");
for (i = 0; i < info->hdr->e_shnum; i++) {
--
2.24.1
next prev parent reply other threads:[~2020-02-05 22:41 UTC|newest]
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 ` [RFC PATCH 09/11] kallsyms: hide layout and expose seed Kristen Carlson Accardi
2020-02-06 12:32 ` 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 ` Kristen Carlson Accardi [this message]
2020-02-06 12:41 ` [RFC PATCH 10/11] module: Reorder functions 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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200205223950.1212394-11-kristen@linux.intel.com \
--to=kristen@linux.intel.com \
--cc=arjan@linux.intel.com \
--cc=bp@alien8.de \
--cc=hpa@zytor.com \
--cc=keescook@chromium.org \
--cc=kernel-hardening@lists.openwall.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=rick.p.edgecombe@intel.com \
--cc=tglx@linutronix.de \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).