pve-edge-kernel/patches/kernel/0023-module-retpoline-Warn-about-missing-retpoline-in-mod.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Andi Kleen <[email protected]>
Date: Thu, 25 Jan 2018 15:50:28 -0800
Subject: [PATCH] module/retpoline: Warn about missing retpoline in module
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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 <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Cc: David Woodhouse <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Link: https://lkml.kernel.org/r/[email protected]
(backported from commit caf7501a1b4ec964190f31f9c3f163de252273b8)
Conflicts:
	arch/x86/kernel/cpu/bugs.c
context changes
Signed-off-by: Fabian Grünbichler <[email protected]>
---
 include/linux/module.h     |  9 +++++++++
 arch/x86/kernel/cpu/bugs.c | 19 +++++++++++++++++--
 kernel/module.c            | 11 +++++++++++
 scripts/mod/modpost.c      |  9 +++++++++
 4 files changed, 46 insertions(+), 2 deletions(-)

diff --git a/include/linux/module.h b/include/linux/module.h
index e7bdd549e527..c4fdf7661f82 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/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index d5bafcdb4891..e623bd731a74 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -11,6 +11,7 @@
 #include <linux/utsname.h>
 #include <linux/cpu.h>
 #include <linux/smp.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)
 {
@@ -299,7 +313,8 @@ 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%s\n", spectre_v2_strings[spectre_v2_enabled],
-		       ibpb_inuse ? ", IBPB (Intel v4)" : "");
+	return sprintf(buf, "%s%s%s\n", spectre_v2_strings[spectre_v2_enabled],
+		       ibpb_inuse ? ", IBPB (Intel v4)" : "",
+		       spectre_v2_bad_module ? " - vulnerable module loaded" : "");
 }
 #endif
diff --git a/kernel/module.c b/kernel/module.c
index e5b878b26906..de7db074f793 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 48397feb08fb..cc91f81ac33e 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -2147,6 +2147,14 @@ 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";
@@ -2492,6 +2500,7 @@ 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);
-- 
2.14.2