linux-kernel - Re: [PATCH] prctl: fix PR_SET_MM

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Message-ID: <YE6LswIxL1N+8AS4@grain>
Date:   Mon, 15 Mar 2021 01:18:27 +0300
From:   Cyrill Gorcunov <gorcunov@...il.com>
To:     Alexey Dobriyan <adobriyan@...il.com>
Cc:     akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
        security@...nel.org
Subject: Re: [PATCH] prctl: fix PR_SET_MM_AUXV kernel stack leak

On Sun, Mar 14, 2021 at 11:51:14PM +0300, Alexey Dobriyan wrote:
> 	prctl(PR_SET_MM, PR_SET_MM_AUXV, addr, 1);
> 
> will copy 1 byte from userspace to (quite big) on-stack array
> and then stash everything to mm->saved_auxv.
> AT_NULL terminator will be inserted at the very end.
> 
> /proc/*/auxv handler will find that AT_NULL terminator
> and copy original stack contents to userspace.
> 
> This devious scheme requires CAP_SYS_RESOURCE.
> 
> Signed-off-by: Alexey Dobriyan <adobriyan@...il.com>
> ---

Thanks for catching up, Alexey!