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module/retpoline: Warn about missing retpoline in module
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
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4 changed files with 45 additions and 1 deletions
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@ -11,6 +11,7 @@
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#include <linux/init.h>
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#include <linux/utsname.h>
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#include <linux/cpu.h>
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#include <linux/module.h>
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#include <asm/nospec-branch.h>
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#include <asm/cmdline.h>
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@ -93,6 +94,19 @@ static const char *spectre_v2_strings[] = {
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#define pr_fmt(fmt) "Spectre V2 mitigation: " fmt
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static enum spectre_v2_mitigation spectre_v2_enabled = SPECTRE_V2_NONE;
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static bool spectre_v2_bad_module;
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#ifdef RETPOLINE
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bool retpoline_module_ok(bool has_retpoline)
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{
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if (spectre_v2_enabled == SPECTRE_V2_NONE || has_retpoline)
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return true;
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pr_err("System may be vunerable to spectre v2\n");
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spectre_v2_bad_module = true;
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return false;
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}
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#endif
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static void __init spec2_print_if_insecure(const char *reason)
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{
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@ -278,6 +292,7 @@ ssize_t cpu_show_spectre_v2(struct device *dev,
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if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V2))
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return sprintf(buf, "Not affected\n");
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return sprintf(buf, "%s\n", spectre_v2_strings[spectre_v2_enabled]);
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return sprintf(buf, "%s%s\n", spectre_v2_strings[spectre_v2_enabled],
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spectre_v2_bad_module ? " - vulnerable module loaded" : "");
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}
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#endif
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@ -794,6 +794,15 @@ static inline void module_bug_finalize(const Elf_Ehdr *hdr,
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static inline void module_bug_cleanup(struct module *mod) {}
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#endif /* CONFIG_GENERIC_BUG */
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#ifdef RETPOLINE
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extern bool retpoline_module_ok(bool has_retpoline);
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#else
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static inline bool retpoline_module_ok(bool has_retpoline)
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{
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return true;
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}
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#endif
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#ifdef CONFIG_MODULE_SIG
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static inline bool module_sig_ok(struct module *module)
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{
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@ -2855,6 +2855,15 @@ static int check_modinfo_livepatch(struct module *mod, struct load_info *info)
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}
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#endif /* CONFIG_LIVEPATCH */
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static void check_modinfo_retpoline(struct module *mod, struct load_info *info)
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{
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if (retpoline_module_ok(get_modinfo(info, "retpoline")))
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return;
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pr_warn("%s: loading module not compiled with retpoline compiler.\n",
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mod->name);
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}
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/* Sets info->hdr and info->len. */
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static int copy_module_from_user(const void __user *umod, unsigned long len,
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struct load_info *info)
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@ -3021,6 +3030,8 @@ static int check_modinfo(struct module *mod, struct load_info *info, int flags)
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add_taint_module(mod, TAINT_OOT_MODULE, LOCKDEP_STILL_OK);
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}
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check_modinfo_retpoline(mod, info);
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if (get_modinfo(info, "staging")) {
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add_taint_module(mod, TAINT_CRAP, LOCKDEP_STILL_OK);
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pr_warn("%s: module is from the staging directory, the quality "
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@ -2165,6 +2165,14 @@ static void add_intree_flag(struct buffer *b, int is_intree)
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buf_printf(b, "\nMODULE_INFO(intree, \"Y\");\n");
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}
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/* Cannot check for assembler */
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static void add_retpoline(struct buffer *b)
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{
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buf_printf(b, "\n#ifdef RETPOLINE\n");
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buf_printf(b, "MODULE_INFO(retpoline, \"Y\");\n");
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buf_printf(b, "#endif\n");
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}
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static void add_staging_flag(struct buffer *b, const char *name)
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{
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static const char *staging_dir = "drivers/staging";
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@ -2506,6 +2514,7 @@ int main(int argc, char **argv)
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err |= check_modname_len(mod);
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add_header(&buf, mod);
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add_intree_flag(&buf, !external_module);
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add_retpoline(&buf);
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add_staging_flag(&buf, mod->name);
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err |= add_versions(&buf, mod);
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add_depends(&buf, mod, modules);
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