linux-kernel - Re: [PATCH] x86/mm/mem_encrypt: fix a crash with kmemleak

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Message-ID: <20190418074510.GB27160@zn.tnic>
Date:   Thu, 18 Apr 2019 09:45:10 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Qian Cai <cai@....pw>
Cc:     dave.hansen@...ux.intel.com, luto@...nel.org, peterz@...radead.org,
        catalin.marinas@....com, tglx@...utronix.de, mingo@...hat.com,
        x86@...nel.org, linux-kernel@...r.kernel.org,
        Brijesh Singh <brijesh.singh@....com>
Subject: Re: [PATCH] x86/mm/mem_encrypt: fix a crash with kmemleak_scan

On Tue, Apr 16, 2019 at 08:38:30PM -0400, Qian Cai wrote:
> kmemleak_init() will register the data/bss sections (only register
> .data..ro_after_init if not within .data) and then kmemleak_scan() will scan
> those address and dereference them looking for pointer referencing. If
> free_init_pages() free and unmap pages in those sections, kmemleak_scan() will
> trigger a crash if referencing one of those addresses.
>
> I checked other x86 free_init_pages() call sites and don't see anything obvious
> where another place to free an address in those sections.

And why is .bss/.data special and why does it need that special handling
by kmemleak?

There must be some rule or a heuristic why kmemleak does that. Is that
documented somewhere?

Thx.

-- 
Regards/Gruss,
    Boris.

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