patches/kernel/0015-module-retpoline-Warn-about-missing-retpoline-in-mod.patch

   1 From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
   2 From: Andi Kleen <ak@linux.intel.com>
   3 Date: Thu, 25 Jan 2018 15:50:28 -0800
   4 Subject: [PATCH] module/retpoline: Warn about missing retpoline in module
   5 MIME-Version: 1.0
   6 Content-Type: text/plain; charset=UTF-8
   7 Content-Transfer-Encoding: 8bit
   8
   9 There's a risk that a kernel which has full retpoline mitigations becomes
  10 vulnerable when a module gets loaded that hasn't been compiled with the
  11 right compiler or the right option.
  12
  13 To enable detection of that mismatch at module load time, add a module info
  14 string "retpoline" at build time when the module was compiled with
  15 retpoline support. This only covers compiled C source, but assembler source
  16 or prebuilt object files are not checked.
  17
  18 If a retpoline enabled kernel detects a non retpoline protected module at
  19 load time, print a warning and report it in the sysfs vulnerability file.
  20
  21 [ tglx: Massaged changelog ]
  22
  23 Signed-off-by: Andi Kleen <ak@linux.intel.com>
  24 Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
  25 Cc: David Woodhouse <dwmw2@infradead.org>
  26 Cc: gregkh@linuxfoundation.org
  27 Cc: torvalds@linux-foundation.org
  28 Cc: jeyu@kernel.org
  29 Cc: arjan@linux.intel.com
  30 Link: https://lkml.kernel.org/r/20180125235028.31211-1-andi@firstfloor.org
  31 (backported from commit caf7501a1b4ec964190f31f9c3f163de252273b8)
  32 Conflicts:
  33         arch/x86/kernel/cpu/bugs.c
  34 context changes
  35 Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
  36 ---
  37  include/linux/module.h     |  9 +++++++++
  38  arch/x86/kernel/cpu/bugs.c | 19 +++++++++++++++++--
  39  kernel/module.c            | 11 +++++++++++
  40  scripts/mod/modpost.c      |  9 +++++++++
  41  4 files changed, 46 insertions(+), 2 deletions(-)
  42
  43 diff --git a/include/linux/module.h b/include/linux/module.h
  44 index e7bdd549e527..c4fdf7661f82 100644
  45 --- a/include/linux/module.h
  46 +++ b/include/linux/module.h
  47 @@ -794,6 +794,15 @@ static inline void module_bug_finalize(const Elf_Ehdr *hdr,
  48  static inline void module_bug_cleanup(struct module *mod) {}
  49  #endif /* CONFIG_GENERIC_BUG */
  50
  51 +#ifdef RETPOLINE
  52 +extern bool retpoline_module_ok(bool has_retpoline);
  53 +#else
  54 +static inline bool retpoline_module_ok(bool has_retpoline)
  55 +{
  56 +       return true;
  57 +}
  58 +#endif
  59 +
  60  #ifdef CONFIG_MODULE_SIG
  61  static inline bool module_sig_ok(struct module *module)
  62  {
  63 diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
  64 index d5bafcdb4891..e623bd731a74 100644
  65 --- a/arch/x86/kernel/cpu/bugs.c
  66 +++ b/arch/x86/kernel/cpu/bugs.c
  67 @@ -11,6 +11,7 @@
  68  #include <linux/utsname.h>
  69  #include <linux/cpu.h>
  70  #include <linux/smp.h>
  71 +#include <linux/module.h>
  72
  73  #include <asm/nospec-branch.h>
  74  #include <asm/cmdline.h>
  75 @@ -93,6 +94,19 @@ static const char *spectre_v2_strings[] = {
  76  #define pr_fmt(fmt)     "Spectre V2 mitigation: " fmt
  77
  78  static enum spectre_v2_mitigation spectre_v2_enabled = SPECTRE_V2_NONE;
  79 +static bool spectre_v2_bad_module;
  80 +
  81 +#ifdef RETPOLINE
  82 +bool retpoline_module_ok(bool has_retpoline)
  83 +{
  84 +       if (spectre_v2_enabled == SPECTRE_V2_NONE || has_retpoline)
  85 +               return true;
  86 +
  87 +       pr_err("System may be vunerable to spectre v2\n");
  88 +       spectre_v2_bad_module = true;
  89 +       return false;
  90 +}
  91 +#endif
  92
  93  static void __init spec2_print_if_insecure(const char *reason)
  94  {
  95 @@ -299,7 +313,8 @@ ssize_t cpu_show_spectre_v2(struct device *dev,
  96         if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V2))
  97                 return sprintf(buf, "Not affected\n");
  98
  99 -       return sprintf(buf, "%s%s\n", spectre_v2_strings[spectre_v2_enabled],
 100 -                      ibpb_inuse ? ", IBPB (Intel v4)" : "");
 101 +       return sprintf(buf, "%s%s%s\n", spectre_v2_strings[spectre_v2_enabled],
 102 +                      ibpb_inuse ? ", IBPB (Intel v4)" : "",
 103 +                      spectre_v2_bad_module ? " - vulnerable module loaded" : "");
 104  }
 105  #endif
 106 diff --git a/kernel/module.c b/kernel/module.c
 107 index e5b878b26906..de7db074f793 100644
 108 --- a/kernel/module.c
 109 +++ b/kernel/module.c
 110 @@ -2855,6 +2855,15 @@ static int check_modinfo_livepatch(struct module *mod, struct load_info *info)
 111  }
 112  #endif /* CONFIG_LIVEPATCH */
 113
 114 +static void check_modinfo_retpoline(struct module *mod, struct load_info *info)
 115 +{
 116 +       if (retpoline_module_ok(get_modinfo(info, "retpoline")))
 117 +               return;
 118 +
 119 +       pr_warn("%s: loading module not compiled with retpoline compiler.\n",
 120 +               mod->name);
 121 +}
 122 +
 123  /* Sets info->hdr and info->len. */
 124  static int copy_module_from_user(const void __user *umod, unsigned long len,
 125                                   struct load_info *info)
 126 @@ -3021,6 +3030,8 @@ static int check_modinfo(struct module *mod, struct load_info *info, int flags)
 127                 add_taint_module(mod, TAINT_OOT_MODULE, LOCKDEP_STILL_OK);
 128         }
 129
 130 +       check_modinfo_retpoline(mod, info);
 131 +
 132         if (get_modinfo(info, "staging")) {
 133                 add_taint_module(mod, TAINT_CRAP, LOCKDEP_STILL_OK);
 134                 pr_warn("%s: module is from the staging directory, the quality "
 135 diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
 136 index 48397feb08fb..cc91f81ac33e 100644
 137 --- a/scripts/mod/modpost.c
 138 +++ b/scripts/mod/modpost.c
 139 @@ -2147,6 +2147,14 @@ static void add_intree_flag(struct buffer *b, int is_intree)
 140                 buf_printf(b, "\nMODULE_INFO(intree, \"Y\");\n");
 141  }
 142
 143 +/* Cannot check for assembler */
 144 +static void add_retpoline(struct buffer *b)
 145 +{
 146 +       buf_printf(b, "\n#ifdef RETPOLINE\n");
 147 +       buf_printf(b, "MODULE_INFO(retpoline, \"Y\");\n");
 148 +       buf_printf(b, "#endif\n");
 149 +}
 150 +
 151  static void add_staging_flag(struct buffer *b, const char *name)
 152  {
 153         static const char *staging_dir = "drivers/staging";
 154 @@ -2492,6 +2500,7 @@ int main(int argc, char **argv)
 155
 156                 add_header(&buf, mod);
 157                 add_intree_flag(&buf, !external_module);
 158 +               add_retpoline(&buf);
 159                 add_staging_flag(&buf, mod->name);
 160                 err |= add_versions(&buf, mod);
 161                 add_depends(&buf, mod, modules);
 162 --
 163 2.14.2
 164