linux-kernel - Re: [PATCH v4] x86/boot: Use efi_setup_data for searching RSDP on kexec-ed kernel

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Message-ID: <20190411083738.GC30080@zn.tnic>
Date:   Thu, 11 Apr 2019 10:37:38 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Junichi Nomura <j-nomura@...jp.nec.com>
Cc:     Dave Young <dyoung@...hat.com>,
        Chao Fan <fanc.fnst@...fujitsu.com>,
        Baoquan He <bhe@...hat.com>, Kairui Song <kasong@...hat.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "kexec@...ts.infradead.org" <kexec@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4] x86/boot: Use efi_setup_data for searching RSDP on
 kexec-ed kernel

On Thu, Apr 11, 2019 at 08:16:45AM +0000, Junichi Nomura wrote:
> kexec_get_rsdp_addr() might fail on kexec-booted kernel, e.g. if the
> setup_data was invalid. In such a case, falling back to efi_get_rsdp_addr()
> will hit the problem of accessing invalid table pointer again.

Then you need to do this:

	if (kexeced kernel) {
		addr = kexec_get_rsdp_addr();
		if (!addr) {
			/* cannot get address */
			return -1;
		}

		return addr;
	}

and the calling function get_rsdp_addr() must check the return value and
if it is not 0, return immediately.

-- 
Regards/Gruss,
    Boris.

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