All of lore.kernel.org
 help / color / mirror / Atom feed
From: tip-bot for Andi Kleen <tipbot@zytor.com>
To: linux-tip-commits@vger.kernel.org
Cc: dwmw2@infradead.org, hpa@zytor.com, linux-kernel@vger.kernel.org,
	tglx@linutronix.de, mingo@kernel.org, ak@linux.intel.com
Subject: [tip:x86/pti] module/retpoline: Warn about missing retpoline in module
Date: Fri, 26 Jan 2018 06:59:06 -0800	[thread overview]
Message-ID: <tip-caf7501a1b4ec964190f31f9c3f163de252273b8@git.kernel.org> (raw)
In-Reply-To: <20180125235028.31211-1-andi@firstfloor.org>

Commit-ID:  caf7501a1b4ec964190f31f9c3f163de252273b8
Gitweb:     https://git.kernel.org/tip/caf7501a1b4ec964190f31f9c3f163de252273b8
Author:     Andi Kleen <ak@linux.intel.com>
AuthorDate: Thu, 25 Jan 2018 15:50:28 -0800
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Fri, 26 Jan 2018 15:03:56 +0100

module/retpoline: Warn about missing retpoline in module

There's a risk that a kernel which has full retpoline mitigations becomes
vulnerable when a module gets loaded that hasn't been compiled with the
right compiler or the right option.

To enable detection of that mismatch at module load time, add a module info
string "retpoline" at build time when the module was compiled with
retpoline support. This only covers compiled C source, but assembler source
or prebuilt object files are not checked.

If a retpoline enabled kernel detects a non retpoline protected module at
load time, print a warning and report it in the sysfs vulnerability file.

[ tglx: Massaged changelog ]

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: gregkh@linuxfoundation.org
Cc: torvalds@linux-foundation.org
Cc: jeyu@kernel.org
Cc: arjan@linux.intel.com
Link: https://lkml.kernel.org/r/20180125235028.31211-1-andi@firstfloor.org
---
 arch/x86/kernel/cpu/bugs.c | 17 ++++++++++++++++-
 include/linux/module.h     |  9 +++++++++
 kernel/module.c            | 11 +++++++++++
 scripts/mod/modpost.c      |  9 +++++++++
 4 files changed, 45 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 390b3dc..4a39d7b 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -11,6 +11,7 @@
 #include <linux/init.h>
 #include <linux/utsname.h>
 #include <linux/cpu.h>
+#include <linux/module.h>
 
 #include <asm/nospec-branch.h>
 #include <asm/cmdline.h>
@@ -93,6 +94,19 @@ static const char *spectre_v2_strings[] = {
 #define pr_fmt(fmt)     "Spectre V2 mitigation: " fmt
 
 static enum spectre_v2_mitigation spectre_v2_enabled = SPECTRE_V2_NONE;
+static bool spectre_v2_bad_module;
+
+#ifdef RETPOLINE
+bool retpoline_module_ok(bool has_retpoline)
+{
+	if (spectre_v2_enabled == SPECTRE_V2_NONE || has_retpoline)
+		return true;
+
+	pr_err("System may be vunerable to spectre v2\n");
+	spectre_v2_bad_module = true;
+	return false;
+}
+#endif
 
 static void __init spec2_print_if_insecure(const char *reason)
 {
@@ -278,6 +292,7 @@ ssize_t cpu_show_spectre_v2(struct device *dev,
 	if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V2))
 		return sprintf(buf, "Not affected\n");
 
-	return sprintf(buf, "%s\n", spectre_v2_strings[spectre_v2_enabled]);
+	return sprintf(buf, "%s%s\n", spectre_v2_strings[spectre_v2_enabled],
+		       spectre_v2_bad_module ? " - vulnerable module loaded" : "");
 }
 #endif
diff --git a/include/linux/module.h b/include/linux/module.h
index fe5aa37..b1cc541 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -794,6 +794,15 @@ static inline void module_bug_finalize(const Elf_Ehdr *hdr,
 static inline void module_bug_cleanup(struct module *mod) {}
 #endif	/* CONFIG_GENERIC_BUG */
 
+#ifdef RETPOLINE
+extern bool retpoline_module_ok(bool has_retpoline);
+#else
+static inline bool retpoline_module_ok(bool has_retpoline)
+{
+	return true;
+}
+#endif
+
 #ifdef CONFIG_MODULE_SIG
 static inline bool module_sig_ok(struct module *module)
 {
diff --git a/kernel/module.c b/kernel/module.c
index de66ec8..690c065 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2855,6 +2855,15 @@ static int check_modinfo_livepatch(struct module *mod, struct load_info *info)
 }
 #endif /* CONFIG_LIVEPATCH */
 
+static void check_modinfo_retpoline(struct module *mod, struct load_info *info)
+{
+	if (retpoline_module_ok(get_modinfo(info, "retpoline")))
+		return;
+
+	pr_warn("%s: loading module not compiled with retpoline compiler.\n",
+		mod->name);
+}
+
 /* Sets info->hdr and info->len. */
 static int copy_module_from_user(const void __user *umod, unsigned long len,
 				  struct load_info *info)
@@ -3021,6 +3030,8 @@ static int check_modinfo(struct module *mod, struct load_info *info, int flags)
 		add_taint_module(mod, TAINT_OOT_MODULE, LOCKDEP_STILL_OK);
 	}
 
+	check_modinfo_retpoline(mod, info);
+
 	if (get_modinfo(info, "staging")) {
 		add_taint_module(mod, TAINT_CRAP, LOCKDEP_STILL_OK);
 		pr_warn("%s: module is from the staging directory, the quality "
diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index 98314b4..54deaa1 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -2165,6 +2165,14 @@ static void add_intree_flag(struct buffer *b, int is_intree)
 		buf_printf(b, "\nMODULE_INFO(intree, \"Y\");\n");
 }
 
+/* Cannot check for assembler */
+static void add_retpoline(struct buffer *b)
+{
+	buf_printf(b, "\n#ifdef RETPOLINE\n");
+	buf_printf(b, "MODULE_INFO(retpoline, \"Y\");\n");
+	buf_printf(b, "#endif\n");
+}
+
 static void add_staging_flag(struct buffer *b, const char *name)
 {
 	static const char *staging_dir = "drivers/staging";
@@ -2506,6 +2514,7 @@ int main(int argc, char **argv)
 		err |= check_modname_len(mod);
 		add_header(&buf, mod);
 		add_intree_flag(&buf, !external_module);
+		add_retpoline(&buf);
 		add_staging_flag(&buf, mod->name);
 		err |= add_versions(&buf, mod);
 		add_depends(&buf, mod, modules);

  parent reply	other threads:[~2018-01-26 15:03 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-01-25 23:50 [PATCH v4] retpoline/module: Warn for " Andi Kleen
2018-01-25 23:53 ` Randy Dunlap
2018-01-26 14:59 ` tip-bot for Andi Kleen [this message]
2018-01-26 17:51   ` [tip:x86/pti] module/retpoline: Warn about " Randy Dunlap
2018-01-27 13:40   ` Borislav Petkov

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=tip-caf7501a1b4ec964190f31f9c3f163de252273b8@git.kernel.org \
    --to=tipbot@zytor.com \
    --cc=ak@linux.intel.com \
    --cc=dwmw2@infradead.org \
    --cc=hpa@zytor.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-tip-commits@vger.kernel.org \
    --cc=mingo@kernel.org \
    --cc=tglx@linutronix.de \
    --subject='Re: [tip:x86/pti] module/retpoline: Warn about missing retpoline in module' \
    /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

This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.