[tip:x86/pti] module: Add retpoline tag to VERMAGIC

[tip-bot for Andi Kleen]

Commit-ID:  6cfb521ac0d5b97470883ff9b7facae264b7ab12
Gitweb:     https://git.kernel.org/tip/6cfb521ac0d5b97470883ff9b7facae264b7ab12
Author:     Andi Kleen <ak@xxxxxxxxxxxxxxx>
AuthorDate: Tue, 16 Jan 2018 12:52:28 -0800
Committer:  Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitDate: Wed, 17 Jan 2018 11:35:14 +0100

module: Add retpoline tag to VERMAGIC

Add a marker for retpoline to the module VERMAGIC. This catches the case
when a non RETPOLINE compiled module gets loaded into a retpoline kernel,
making it insecure.

It doesn't handle the case when retpoline has been runtime disabled.  Even
in this case the match of the retcompile status will be enforced.  This
implies that even with retpoline run time disabled all modules loaded need
to be recompiled.

Signed-off-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Reviewed-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Acked-by: David Woodhouse <dwmw@xxxxxxxxxxxx>
Cc: rusty@xxxxxxxxxxxxxxx
Cc: arjan.van.de.ven@xxxxxxxxx
Cc: jeyu@xxxxxxxxxx
Cc: torvalds@xxxxxxxxxxxxxxxxxxxx
Link: https://lkml.kernel.org/r/20180116205228.4890-1-andi@xxxxxxxxxxxxxx
---
 include/linux/vermagic.h | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/include/linux/vermagic.h b/include/linux/vermagic.h
index bae807e..8532917 100644
--- a/include/linux/vermagic.h
+++ b/include/linux/vermagic.h
@@ -31,11 +31,17 @@
 #else
 #define MODULE_RANDSTRUCT_PLUGIN
 #endif
+#ifdef RETPOLINE
+#define MODULE_VERMAGIC_RETPOLINE "retpoline "
+#else
+#define MODULE_VERMAGIC_RETPOLINE ""
+#endif
 
 #define VERMAGIC_STRING 						\
 	UTS_RELEASE " "							\
 	MODULE_VERMAGIC_SMP MODULE_VERMAGIC_PREEMPT 			\
 	MODULE_VERMAGIC_MODULE_UNLOAD MODULE_VERMAGIC_MODVERSIONS	\
 	MODULE_ARCH_VERMAGIC						\
-	MODULE_RANDSTRUCT_PLUGIN
+	MODULE_RANDSTRUCT_PLUGIN					\
+	MODULE_VERMAGIC_RETPOLINE