linux-kernel - Re: [PATCH v4 2/2] x86/boot/KASLR: skip the specified crashkernel region

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Message-ID: <20190417160618.GG20492@zn.tnic>
Date:   Wed, 17 Apr 2019 18:06:18 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Pingfan Liu <kernelfans@...il.com>
Cc:     x86@...nel.org, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, Baoquan He <bhe@...hat.com>,
        Will Deacon <will.deacon@....com>,
        Nicolas Pitre <nico@...aro.org>,
        Vivek Goyal <vgoyal@...hat.com>,
        Chao Fan <fanc.fnst@...fujitsu.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Hari Bathini <hbathini@...ux.vnet.ibm.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 2/2] x86/boot/KASLR: skip the specified crashkernel
 region

On Wed, Apr 17, 2019 at 01:53:37PM +0800, Pingfan Liu wrote:
> Take __parse_crashkernel()->parse_crashkernel_simple() for example. If
> no offset given, then it still return 0, but crash_base is dangling.

Well, that is bad design. parse_crashkernel_simple() should return a
*separate* distinct value which denotes that @offset hasn't been passed.

Please fix that by having it return 1 or something else positive to
denote that there wasn't an [@offset] given.

And then correct that crap here:

static void __init reserve_crashkernel(void)
{
	...

        ret = parse_crashkernel(boot_command_line, total_mem, &crash_size, &crash_base);
        if (ret != 0 || crash_size <= 0) {

where *two*! variables are used as return values from a single function.
That's just sloppy.

Thx.

-- 
Regards/Gruss,
    Boris.

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