From 6cd5513c813eb57eba081563beb817abd9923a3a Mon Sep 17 00:00:00 2001 From: Andi Kleen Date: Fri, 23 Feb 2018 11:41:54 +0100 Subject: module/retpoline: Warn about missing retpoline in module (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 Signed-off-by: Thomas Gleixner Cc: David Woodhouse 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 [jwang: port to 4.4] Signed-off-by: Jack Wang Signed-off-by: Greg Kroah-Hartman --- 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(-) diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index 8cacf62ec458..b86e0a2f1b48 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -10,6 +10,7 @@ #include #include #include +#include #include #include @@ -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 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 b229a9961d02..c9f2f85017ad 100644 --- a/include/linux/module.h +++ b/include/linux/module.h @@ -789,6 +789,15 @@ 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 0a56098d3738..aa81f41f2b19 100644 --- a/kernel/module.c +++ b/kernel/module.c @@ -2869,6 +2869,15 @@ static struct module *setup_load_info(struct load_info *info, int flags) 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 *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 48958d3cec9e..bd5151915e5a 100644 --- a/scripts/mod/modpost.c +++ b/scripts/mod/modpost.c @@ -2129,6 +2129,14 @@ 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"; @@ -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); -- cgit v1.2.3