linux-kernel - Re: [lkp-robot] [include/linux/string.h] 6974f0c455: kernel_BUG_at

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Message-ID: <1500523343.2055.2.camel@gmail.com>
Date:   Thu, 20 Jul 2017 00:02:23 -0400
From:   Daniel Micay <danielmicay@...il.com>
To:     kernel test robot <xiaolong.ye@...el.com>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Kees Cook <keescook@...omium.org>,
        Arnd Bergmann <arnd@...db.de>,
        Mark Rutland <mark.rutland@....com>,
        Daniel Axtens <dja@...ens.net>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Chris Metcalf <cmetcalf@...hip.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...e.hu>,
        Andrew Morton <akpm@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>, lkp@...org
Subject: Re: [lkp-robot] [include/linux/string.h]  6974f0c455:
 kernel_BUG_at_lib/string.c

> [    8.134886]  arch_prepare_optimized_kprobe+0xd5/0x171
> [    8.134886]  arch_prepare_optimized_kprobe+0xd5/0x171

Probably this:

	/* Copy arch-dep-instance from template */
	memcpy(buf, &optprobe_template_entry, TMPL_END_IDX);

Not a real bug, just technically undefined because these are u32:

typedef u32 kprobe_opcode_t;

extern __visible kprobe_opcode_t optprobe_template_entry;
extern __visible kprobe_opcode_t optprobe_template_val;
extern __visible kprobe_opcode_t optprobe_template_call;
extern __visible kprobe_opcode_t optprobe_template_end;
extern __visible kprobe_opcode_t optprobe_template_sub_sp;
extern __visible kprobe_opcode_t optprobe_template_add_sp;
extern __visible kprobe_opcode_t optprobe_template_restore_begin;
extern __visible kprobe_opcode_t optprobe_template_restore_orig_insn;
extern __visible kprobe_opcode_t optprobe_template_restore_end;

Could be switched to unknown size arrays like optprobe_template_entry[]
but it might be best to just mark the kprobe code with #define
__NO_FORTIFY.