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From: Cyrill Gorcunov <gorcunov@gmail.com>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>,
	akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
	security@kernel.org
Subject: Re: [PATCH] prctl: fix PR_SET_MM_AUXV kernel stack leak
Date: Mon, 15 Mar 2021 15:54:50 +0300	[thread overview]
Message-ID: <YE9ZGl9jlnDz1OBP@grain> (raw)
In-Reply-To: <20210315120803.GA13620@redhat.com>

On Mon, Mar 15, 2021 at 01:08:03PM +0100, Oleg Nesterov wrote:
> On 03/14, 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.
> 
> I too don't understand, memcpy(mm->saved_auxv, user_auxv, len) will
> copy 1 byte...

Indeed. I overlooked that we pass @len when copying. I should
not reply at night :(

> 
> And why task_lock(current) ? What does it try to protect?

As far as I remember this was related to reading from procfs
at time the patch was written for first time. Looks like this
not relevant anymore and could be dropped.

  reply	other threads:[~2021-03-15 12:55 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-14 20:51 [PATCH] prctl: fix PR_SET_MM_AUXV kernel stack leak Alexey Dobriyan
2021-03-14 21:40 ` Linus Torvalds
2021-03-14 22:24   ` Cyrill Gorcunov
2021-03-15  6:00   ` auxv stuff (Re: [PATCH] prctl: fix PR_SET_MM_AUXV kernel stack leak) Alexey Dobriyan
2021-03-15  6:42     ` Cyrill Gorcunov
2021-03-16 18:50       ` Alexey Dobriyan
2021-03-16 18:51         ` Cyrill Gorcunov
2021-03-14 22:18 ` [PATCH] prctl: fix PR_SET_MM_AUXV kernel stack leak Cyrill Gorcunov
2021-03-15 10:29 ` Dan Carpenter
2021-03-15 13:30   ` Alexey Dobriyan
2021-03-15 12:08 ` Oleg Nesterov
2021-03-15 12:54   ` Cyrill Gorcunov [this message]
2021-03-15 13:19     ` Oleg Nesterov
2021-03-15 13:52       ` Cyrill Gorcunov

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