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 4.14-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:
moduleretpoline_Warn_about_missing_retpoline_in_module.patch
and it can be found in the queue-4.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
Subject: module/retpoline: Warn about missing retpoline in module
From: Andi Kleen ak@xxxxxxxxxxxxxxx
Date: Thu Jan 25 15:50:28 2018 -0800
From: Andi Kleen ak@xxxxxxxxxxxxxxx
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@xxxxxxxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: David Woodhouse <dwmw2@xxxxxxxxxxxxx>
Cc: gregkh@xxxxxxxxxxxxxxxxxxx
Cc: torvalds@xxxxxxxxxxxxxxxxxxxx
Cc: jeyu@xxxxxxxxxx
Cc: arjan@xxxxxxxxxxxxxxx
Link: https://lkml.kernel.org/r/20180125235028.31211-1-andi@xxxxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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(-)
--- 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 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
@@ -794,6 +794,15 @@ 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
@@ -2855,6 +2855,15 @@ static int check_modinfo_livepatch(struc
}
#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 *
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
@@ -2165,6 +2165,14 @@ 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";
@@ -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);
Patches currently in stable-queue which might be from ak@xxxxxxxxxxxxxxx are
queue-4.14/x86pti_Do_not_enable_PTI_on_CPUs_which_are_not_vulnerable_to_Meltdown.patch
queue-4.14/x86cpufeature_Blacklist_SPEC_CTRLPRED_CMD_on_early_Spectre_v2_microcodes.patch
queue-4.14/x86cpufeatures_Add_Intel_feature_bits_for_Speculation_Control.patch
queue-4.14/KVM_VMX_Make_indirect_call_speculation_safe.patch
queue-4.14/x86msr_Add_definitions_for_new_speculation_control_MSRs.patch
queue-4.14/x86alternative_Print_unadorned_pointers.patch
queue-4.14/x86cpubugs_Make_retpoline_module_warning_conditional.patch
queue-4.14/x86cpufeatures_Add_CPUID_7_EDX_CPUID_leaf.patch
queue-4.14/x86retpoline_Remove_the_esprsp_thunk.patch
queue-4.14/x86bugs_Drop_one_mitigation_from_dmesg.patch
queue-4.14/x86cpufeatures_Add_AMD_feature_bits_for_Speculation_Control.patch
queue-4.14/moduleretpoline_Warn_about_missing_retpoline_in_module.patch
queue-4.14/x86speculation_Add_basic_IBPB_(Indirect_Branch_Prediction_Barrier)_support.patch
queue-4.14/x86speculation_Simplify_indirect_branch_prediction_barrier().patch
queue-4.14/x86nospec_Fix_header_guards_names.patch
queue-4.14/KVM_x86_Make_indirect_calls_in_emulator_speculation_safe.patch
queue-4.14/x86retpoline_Simplify_vmexit_fill_RSB().patch
queue-4.14/x86cpufeatures_Clean_up_Spectre_v2_related_CPUID_flags.patch