4.9-stable review patch. If anyone has any objections, please let me know.
------------------
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.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(-)
--- 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> @@ -92,6 +93,19 @@ 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) { @@ -277,6 +291,7 @@ 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 @@ -791,6 +791,15 @@ 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 @@ -2817,6 +2817,15 @@ 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) @@ -2969,6 +2978,8 @@ 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 @@ -2130,6 +2130,14 @@ 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"; @@ -2474,6 +2482,7 @@ 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);