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

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Message-ID: <20190416134443.GF28994@arrakis.emea.arm.com>
Date:   Tue, 16 Apr 2019 14:44:43 +0100
From:   Catalin Marinas <catalin.marinas@....com>
To:     Qian Cai <cai@....pw>
Cc:     dave.hansen@...ux.intel.com, luto@...nel.org, peterz@...radead.org,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/mm/mem_encrypt: fix a crash with kmemleak_scan

On Tue, Apr 09, 2019 at 12:05:02AM -0400, Qian Cai wrote:
> The first kmemleak_scan() after boot would trigger a crash below because
> 
> kernel_init
>   free_initmem
>     mem_encrypt_free_decrypted_mem
>       free_init_pages
> 
> unmapped some memory inside the .bss.
> 
> BUG: unable to handle kernel paging request at ffffffffbd402000
> CPU: 12 PID: 325 Comm: kmemleak Not tainted 5.1.0-rc4+ #4
> RIP: 0010:scan_block+0x58/0x160
> Call Trace:
>  scan_gray_list+0x1d9/0x280
>  kmemleak_scan+0x485/0xad0
>  kmemleak_scan_thread+0x9f/0xc4
>  kthread+0x1d2/0x1f0
>  ret_from_fork+0x35/0x40
> 
> Signed-off-by: Qian Cai <cai@....pw>

It seems that commit 298a32b13208 ("kmemleak: powerpc: skip scanning
holes in the .bss section") has other uses as well.

Acked-by: Catalin Marinas <catalin.marinas@....com>