[PATCH v10 10/18] x86/insn-eval: Do not BUG on invalid register type

Ricardo Neri
2017-10-27T20:31:11Z

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 pr_err().
along with a descriptive prefix.

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
Reviewed-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
---
arch/x86/lib/insn-eval.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/arch/x86/lib/insn-eval.c b/arch/x86/lib/insn-eval.c
index df9418c..4931d92 100644
--- a/arch/x86/lib/insn-eval.c
+++ b/arch/x86/lib/insn-eval.c
@@ -5,10 +5,14 @@
*/
#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>

+#undef pr_fmt
+#define pr_fmt(fmt) "insn: " fmt
+
enum reg_type {
REG_TYPE_RM = 0,
REG_TYPE_INDEX,
@@ -85,9 +89,8 @@ static int get_reg_offset(struct insn *insn, struct pt_regs *regs,
break;

default:
- pr_err("invalid register type");
- BUG();
- break;
+ pr_err_ratelimited("invalid register type: %d\n", type);
+ return -EINVAL;
}

if (regno >= nr_registers) {
--
2.7.4