165 lines
5.5 KiB
Diff
165 lines
5.5 KiB
Diff
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Andi Kleen <ak@linux.intel.com>
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Date: Thu, 25 Jan 2018 15:50:28 -0800
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Subject: [PATCH] module/retpoline: Warn about missing retpoline in module
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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There's a risk that a kernel which has full retpoline mitigations becomes
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vulnerable when a module gets loaded that hasn't been compiled with the
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right compiler or the right option.
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To enable detection of that mismatch at module load time, add a module info
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string "retpoline" at build time when the module was compiled with
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retpoline support. This only covers compiled C source, but assembler source
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or prebuilt object files are not checked.
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If a retpoline enabled kernel detects a non retpoline protected module at
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load time, print a warning and report it in the sysfs vulnerability file.
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[ tglx: Massaged changelog ]
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Signed-off-by: Andi Kleen <ak@linux.intel.com>
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Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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Cc: David Woodhouse <dwmw2@infradead.org>
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Cc: gregkh@linuxfoundation.org
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Cc: torvalds@linux-foundation.org
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Cc: jeyu@kernel.org
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Cc: arjan@linux.intel.com
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Link: https://lkml.kernel.org/r/20180125235028.31211-1-andi@firstfloor.org
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(backported from commit caf7501a1b4ec964190f31f9c3f163de252273b8)
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Conflicts:
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arch/x86/kernel/cpu/bugs.c
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context changes
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Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
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---
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include/linux/module.h | 9 +++++++++
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arch/x86/kernel/cpu/bugs.c | 19 +++++++++++++++++--
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kernel/module.c | 11 +++++++++++
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scripts/mod/modpost.c | 9 +++++++++
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4 files changed, 46 insertions(+), 2 deletions(-)
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diff --git a/include/linux/module.h b/include/linux/module.h
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index e7bdd549e527..c4fdf7661f82 100644
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--- a/include/linux/module.h
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+++ b/include/linux/module.h
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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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+
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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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diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
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index d5bafcdb4891..e623bd731a74 100644
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--- a/arch/x86/kernel/cpu/bugs.c
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+++ b/arch/x86/kernel/cpu/bugs.c
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@@ -11,6 +11,7 @@
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#include <linux/utsname.h>
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#include <linux/cpu.h>
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#include <linux/smp.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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+
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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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+
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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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@@ -299,7 +313,8 @@ 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%s\n", spectre_v2_strings[spectre_v2_enabled],
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- ibpb_inuse ? ", IBPB (Intel v4)" : "");
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+ return sprintf(buf, "%s%s%s\n", spectre_v2_strings[spectre_v2_enabled],
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+ ibpb_inuse ? ", IBPB (Intel v4)" : "",
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+ spectre_v2_bad_module ? " - vulnerable module loaded" : "");
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}
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#endif
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diff --git a/kernel/module.c b/kernel/module.c
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index e5b878b26906..de7db074f793 100644
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--- a/kernel/module.c
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+++ b/kernel/module.c
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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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+
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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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+
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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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+
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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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diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
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index 48397feb08fb..cc91f81ac33e 100644
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--- a/scripts/mod/modpost.c
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+++ b/scripts/mod/modpost.c
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@@ -2147,6 +2147,14 @@ 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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+
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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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@@ -2492,6 +2500,7 @@ int main(int argc, char **argv)
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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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--
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2.14.2
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