Patch "module/retpoline: Warn about missing retpoline in module" has been added to the 4.4-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    module/retpoline: Warn about missing retpoline in module

to the 4.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     module-retpoline-warn-about-missing-retpoline-in-module.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From foo@baz Fri Feb 23 17:23:58 CET 2018
From: Jack Wang <jinpu.wang@profitbricks.com>
Date: Fri, 23 Feb 2018 11:41:54 +0100
Subject: module/retpoline: Warn about missing retpoline in module
To: gregkh@linuxfoundation.org, stable@vger.kernel.org
Cc: Andi Kleen <ak@linux.intel.com>, Thomas Gleixner <tglx@linutronix.de>, David Woodhouse <dwmw2@infradead.org>, torvalds@linux-foundation.org, jeyu@kernel.org, arjan@linux.intel.com, David Woodhouse <dwmw@amazon.co.uk>, Jack Wang <jinpu.wang@profitbricks.com>
Message-ID: <1519382538-15143-6-git-send-email-jinpu.wangl@profitbricks.com>

From: Andi Kleen <ak@linux.intel.com>

(cherry picked from commit caf7501a1b4ec964190f31f9c3f163de252273b8)

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
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
[jwang: port to 4.4]
Signed-off-by: Jack Wang <jinpu.wang@profitbricks.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 arch/x86/kernel/cpu/bugs.c |   18 +++++++++++++++++-
 include/linux/module.h     |    9 +++++++++
 kernel/module.c            |   11 +++++++++++
 scripts/mod/modpost.c      |    9 +++++++++
 4 files changed, 46 insertions(+), 1 deletion(-)

--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -10,6 +10,7 @@
 #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 +94,20 @@ static const char *spectre_v2_strings[]
 
 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)
 {
 	if (boot_cpu_has_bug(X86_BUG_SPECTRE_V2))
@@ -277,6 +292,7 @@ ssize_t cpu_show_spectre_v2(struct devic
 	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
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -789,6 +789,15 @@ static inline void module_bug_finalize(c
 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)
 {
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2869,6 +2869,15 @@ static struct module *setup_load_info(st
 	return mod;
 }
 
+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);
+}
+
 static int check_modinfo(struct module *mod, struct load_info *info, int flags)
 {
 	const char *modmagic = get_modinfo(info, "vermagic");
@@ -2895,6 +2904,8 @@ static int check_modinfo(struct module *
 		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 "
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -2129,6 +2129,14 @@ static void add_intree_flag(struct buffe
 		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";
@@ -2473,6 +2481,7 @@ int main(int argc, char **argv)
 
 		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);


Patches currently in stable-queue which might be from jinpu.wang@profitbricks.com are

queue-4.4/x86-paravirt-remove-noreplace-paravirt-cmdline-option.patch
queue-4.4/documentation-document-array_index_nospec.patch
queue-4.4/kvm-x86-make-indirect-calls-in-emulator-speculation-safe.patch
queue-4.4/x86-nospec-fix-header-guards-names.patch
queue-4.4/x86-retpoline-avoid-retpolines-for-built-in-__init-functions.patch
queue-4.4/vfs-fdtable-prevent-bounds-check-bypass-via-speculative-execution.patch
queue-4.4/kvm-nvmx-invvpid-handling-improvements.patch
queue-4.4/x86-cpu-bugs-make-retpoline-module-warning-conditional.patch
queue-4.4/x86-spectre-check-config_retpoline-in-command-line-parser.patch
queue-4.4/x86-implement-array_index_mask_nospec.patch
queue-4.4/array_index_nospec-sanitize-speculative-array-de-references.patch
queue-4.4/kvm-vmx-make-indirect-call-speculation-safe.patch
queue-4.4/x86-spectre-fix-spelling-mistake-vunerable-vulnerable.patch
queue-4.4/kvm-nvmx-fix-kernel-panics-induced-by-illegal-invept-invvpid-types.patch
queue-4.4/module-retpoline-warn-about-missing-retpoline-in-module.patch
queue-4.4/x86-kvm-update-spectre-v1-mitigation.patch
queue-4.4/x86-get_user-use-pointer-masking-to-limit-speculation.patch
queue-4.4/x86-syscall-sanitize-syscall-table-de-references-under-speculation.patch
queue-4.4/kvm-nvmx-vmx_complete_nested_posted_interrupt-can-t-fail.patch
queue-4.4/x86-spectre-simplify-spectre_v2-command-line-parsing.patch
queue-4.4/x86-speculation-fix-typo-ibrs_att-which-should-be-ibrs_all.patch
queue-4.4/x86-spectre-report-get_user-mitigation-for-spectre_v1.patch
queue-4.4/x86-introduce-barrier_nospec.patch
queue-4.4/kvm-async_pf-fix-df-due-to-inject-page-not-present-and-page-ready-exceptions-simultaneously.patch
queue-4.4/kvm-vmx-clean-up-declaration-of-vpid-ept-invalidation-types.patch
queue-4.4/x86-bugs-drop-one-mitigation-from-dmesg.patch
queue-4.4/x86-retpoline-remove-the-esp-rsp-thunk.patch
queue-4.4/nl80211-sanitize-array-index-in-parse_txq_params.patch
queue-4.4/kvm-nvmx-kmap-can-t-fail.patch