linux-kernel - Re: [PATCH qemu] x86: don't let decompressed kernel image clobber setup

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Message-ID: <Y62MdawGaasXmoVL@zn.tnic>
Date:   Thu, 29 Dec 2022 13:47:49 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     "H. Peter Anvin" <hpa@...or.com>
Cc:     "Jason A. Donenfeld" <Jason@...c4.com>, pbonzini@...hat.com,
        ebiggers@...nel.org, x86@...nel.org, linux-kernel@...r.kernel.org,
        qemu-devel@...gnu.org, ardb@...nel.org, kraxel@...hat.com,
        philmd@...aro.org
Subject: Re: [PATCH qemu] x86: don't let decompressed kernel image clobber
 setup_data

On Wed, Dec 28, 2022 at 11:31:34PM -0800, H. Peter Anvin wrote:
> As far as a crash... that sounds like a big and a pretty serious one at that.
> 
> Could you let me know what kernel you are using and how *exactly* you are booting it?

Right, with CONFIG_X86_VERBOSE_BOOTUP=y in a guest here, it says:

early console in extract_kernel
input_data: 0x000000000be073a8
input_len: 0x00000000008cfc43
output: 0x0000000001000000
output_len: 0x000000000b600a98
kernel_total_size: 0x000000000ac26000
needed_size: 0x000000000b800000
trampoline_32bit: 0x000000000009d000

so that's a ~9M kernel which gets decompressed at 0x1000000 and the
output len is, what, ~180M which looks like plenty to me...

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette