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From: Andy Shevchenko <andy.shevchenko@gmail.com>
Date: Wed, 21 Feb 2018 21:28:41 +0200
Message-ID: <CAHp75VdaxkMn2UxURSB4fWep=iv4CRAkmEtdKBp1HKyxtW2tTg@mail.gmail.com>
Subject: Re: [PATCH 1/5] proc: make /proc/*/cmdline go through LSM
To: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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On Wed, Feb 21, 2018 at 9:23 PM, Alexey Dobriyan <adobriyan@gmail.com> wrote:
> /proc/*/cmdline is not different from /proc/*/environ as it accesses
> target task's memory (and can access the very same region of memory)
> but it doesn't go through ptrace_may_access() and thus doesn't go through LSM.

> +static int __mem_open(struct inode *inode, struct file *file, unsigned int mode)
> +{
> +       struct mm_struct *mm = proc_mem_open(inode, mode);
> +
> +       if (IS_ERR(mm))
> +               return PTR_ERR(mm);

So, is it possible to have it NULL?..

> +
> +       file->private_data = mm;
> +       return 0;
> +}

> +static int mem_release(struct inode *inode, struct file *file)
> +{
> +       struct mm_struct *mm = file->private_data;

> +       if (mm)

...or I don't get this check.

> +               mmdrop(mm);
> +       return 0;
> +}

-- 
With Best Regards,
Andy Shevchenko