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SubjectRe: [PATCH v8 09/28] x86/insn-eval: Do not BUG on invalid register type
On Fri, Aug 18, 2017 at 05:27:50PM -0700, Ricardo Neri wrote:
> 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().
>
> 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 2bb8303ba92f..3919458fecbf 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;
> + pr_err_ratelimited("insn: x86: invalid register type");

Also, I meant to add it to pr_fmt. Feel free to merge this hunk ontop of
yours:

---
diff --git a/arch/x86/lib/insn-eval.c b/arch/x86/lib/insn-eval.c
index 3919458fecbf..d46034ddfbb7 100644
--- a/arch/x86/lib/insn-eval.c
+++ b/arch/x86/lib/insn-eval.c
@@ -10,6 +10,9 @@
#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,
@@ -86,7 +89,7 @@ static int get_reg_offset(struct insn *insn, struct pt_regs *regs,
break;

default:
- pr_err_ratelimited("insn: x86: invalid register type");
+ pr_err_ratelimited("invalid register type: %d\n", type);
return -EINVAL;
}

--
Regards/Gruss,
Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
--

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