[PATCH v7 07/26] x86/insn-eval: Do not BUG on invalid register type

[Ricardo Neri <ricardo.neri-calderon@linux.intel.com>]

We are not in a critical failure path. The invalid register type is caused
when trying to decode invalid instruction bytes from a user-space program.
Thus, simply print an error message. To prevent this warning from being
abused from user space programs, use the rate-limited variant of printk.

Cc: Borislav Petkov <bp@suse.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Adam Buchbinder <adam.buchbinder@gmail.com>
Cc: Colin Ian King <colin.king@canonical.com>
Cc: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Qiaowei Ren <qiaowei.ren@intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Thomas Garnier <thgarnie@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Ravi V. Shankar <ravi.v.shankar@intel.com>
Cc: x86@kernel.org
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
---
 arch/x86/lib/insn-eval.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/lib/insn-eval.c b/arch/x86/lib/insn-eval.c
index e746a6f..182e2ae 100644
--- a/arch/x86/lib/insn-eval.c
+++ b/arch/x86/lib/insn-eval.c
@@ -5,6 +5,7 @@
  */
 #include <linux/kernel.h>
 #include <linux/string.h>
+#include <linux/ratelimit.h>
 #include <asm/inat.h>
 #include <asm/insn.h>
 #include <asm/insn-eval.h>
@@ -85,9 +86,8 @@ static int get_reg_offset(struct insn *insn, struct pt_regs *regs,
 		break;
 
 	default:
-		pr_err("invalid register type");
-		BUG();
-		break;
+		printk_ratelimited(KERN_ERR "insn-eval: x86: invalid register type");
+		return -EINVAL;
 	}
 
 	if (regno >= nr_registers) {
-- 
2.9.3