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Message-ID: <20161019142015.GG19539@ZenIV.linux.org.uk>
Date: Wed, 19 Oct 2016 15:20:15 +0100
From: Al Viro <viro@...IV.linux.org.uk>
To: Leon Yu <chianglungyu@...il.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Kees Cook <keescook@...omium.org>,
Oleg Nesterov <oleg@...hat.com>,
Michal Hocko <mhocko@...e.com>,
John Stultz <john.stultz@...aro.org>,
Mateusz Guzik <mguzik@...hat.com>,
Janis Danisevskis <jdanis@...gle.com>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] proc: fix NULL dereference when reading /proc/<pid>/auxv
On Wed, Oct 19, 2016 at 09:59:40PM +0800, Leon Yu wrote:
> Reading auxv of any kernel thread results in NULL pointer dereferencing in
> auxv_read() where mm can be NULL or even error code. Fix that by testing mm
> with IS_ERR_OR_NULL() helper. This is also the original behavior changed by
> recent commit c5317167854e ("proc: switch auxv to use of __mem_open()").
What the... How can it be ERR_PTR(...) after it has passed __mem_open()?
I agree that we ought to check for NULL mm (the only question is whether it's
best done by failing open() or by treating the file as empty), but this
IS_ERR_OR_NULL() is pure cargo-cult, AFAICS.
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