From a4b1a797a02c1c0b206ecd658aa083ae0ceaa048 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Fabian=20Gr=C3=BCnbichler?= Date: Fri, 16 Feb 2018 08:29:15 +0100 Subject: [PATCH] warn when non-RETPOLINED module gets loaded --- ...-Warn-about-missing-retpoline-in-mod.patch | 164 ++++++++++++++++++ 1 file changed, 164 insertions(+) create mode 100644 patches/kernel/0023-module-retpoline-Warn-about-missing-retpoline-in-mod.patch diff --git a/patches/kernel/0023-module-retpoline-Warn-about-missing-retpoline-in-mod.patch b/patches/kernel/0023-module-retpoline-Warn-about-missing-retpoline-in-mod.patch new file mode 100644 index 0000000..27fffe4 --- /dev/null +++ b/patches/kernel/0023-module-retpoline-Warn-about-missing-retpoline-in-mod.patch @@ -0,0 +1,164 @@ +From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001 +From: Andi Kleen +Date: Thu, 25 Jan 2018 15:50:28 -0800 +Subject: [PATCH] module/retpoline: Warn about missing retpoline in module +MIME-Version: 1.0 +Content-Type: text/plain; charset=UTF-8 +Content-Transfer-Encoding: 8bit + +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 +(backported from commit caf7501a1b4ec964190f31f9c3f163de252273b8) +Conflicts: + arch/x86/kernel/cpu/bugs.c +context changes +Signed-off-by: Fabian Grünbichler +--- + 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 + #include + #include ++#include + + #include + #include +@@ -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 +