From: David Rientjes <rientjes@google.com>
To: Pekka Enberg <penberg@kernel.org>
Cc: Sasha Levin <levinsasha928@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
lizf@cn.fujitsu.com, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, Tyler Hicks <tyhicks@canonical.com>,
Dustin Kirkland <kirkland@canonical.com>,
ecryptfs@vger.kernel.org
Subject: Re: [PATCH] mm: Don't warn if memdup_user fails
Date: Thu, 12 Jan 2012 13:19:54 -0800 (PST) [thread overview]
Message-ID: <alpine.DEB.2.00.1201121309340.17287@chino.kir.corp.google.com> (raw)
In-Reply-To: <CAOJsxLEYY=ZO8QrxiWL6qAxPzsPpZj3RsF9cXY0Q2L44+sn7JQ@mail.gmail.com>
On Thu, 12 Jan 2012, Pekka Enberg wrote:
> I think you missed Andrew's point. We absolutely want to issue a
> kernel warning here because ecryptfs is misusing the memdup_user()
> API. We must not let userspace processes allocate large amounts of
> memory arbitrarily.
>
I think it's good to fix ecryptfs like Tyler is doing and, at the same
time, ensure that the len passed to memdup_user() makes sense prior to
kmallocing memory with GFP_KERNEL. Perhaps something like
if (WARN_ON(len > PAGE_SIZE << PAGE_ALLOC_COSTLY_ORDER))
return ERR_PTR(-ENOMEM);
in which case __GFP_NOWARN is irrelevant. I think memdup_user() should
definitely be taking gfp flags, though, so the caller can specify things
like __GFP_NORETRY on its own to avoid infinitely looping in the page
allocator trying reclaim and possibly calling the oom killer.
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next prev parent reply other threads:[~2012-01-12 21:19 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-11 16:50 Sasha Levin
2012-01-11 21:46 ` David Rientjes
2012-01-12 6:43 ` Pekka Enberg
2012-01-12 6:44 ` Pekka Enberg
2012-01-12 9:09 ` Li Zefan
2012-01-11 22:12 ` Andrew Morton
2012-01-12 7:12 ` Pekka Enberg
2012-01-12 8:06 ` Sasha Levin
2012-01-12 8:15 ` Pekka Enberg
2012-01-12 21:19 ` David Rientjes [this message]
2012-01-12 21:58 ` Andrew Morton
2012-01-12 22:29 ` David Rientjes
2012-01-13 7:17 ` Dan Carpenter
2012-01-13 7:36 ` Andrew Morton
2012-01-12 11:16 ` Tyler Hicks
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