From: Jonathan Corbet <corbet@lwn.net>
To: Mike Rapoport <rppt@kernel.org>
Cc: linux-kernel@vger.kernel.org, Alan Cox <alan@linux.intel.com>,
Andrew Morton <akpm@linux-foundation.org>,
Andy Lutomirski <luto@kernel.org>,
Christopher Lameter <cl@linux.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
James Bottomley <jejb@linux.ibm.com>,
"Kirill A. Shutemov" <kirill@shutemov.name>,
Matthew Wilcox <willy@infradead.org>,
Peter Zijlstra <peterz@infradead.org>,
"Reshetova, Elena" <elena.reshetova@intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
Tycho Andersen <tycho@tycho.ws>,
linux-api@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [RFC PATCH] mm: extend memfd with ability to create "secret" memory areas
Date: Wed, 12 Feb 2020 14:10:29 -0700 [thread overview]
Message-ID: <20200212141029.7b89acee@lwn.net> (raw)
In-Reply-To: <20200130162340.GA14232@rapoport-lnx>
On Thu, 30 Jan 2020 18:23:41 +0200
Mike Rapoport <rppt@kernel.org> wrote:
> Hi,
>
> This is essentially a resend of my attempt to implement "secret" mappings
> using a file descriptor [1].
So one little thing I was curious about as I read through the patch...
> +static int secretmem_check_limits(struct vm_fault *vmf)
> +{
> + struct secretmem_state *state = vmf->vma->vm_file->private_data;
> + struct inode *inode = file_inode(vmf->vma->vm_file);
> + unsigned long limit;
> +
> + if (((loff_t)vmf->pgoff << PAGE_SHIFT) >= i_size_read(inode))
> + return -EINVAL;
> +
> + limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
> + if (state->nr_pages + 1 >= limit)
> + return -EPERM;
> +
> + return 0;
> +}
If I'm not mistaken, this means each memfd can be RLIMIT_MEMLOCK in length,
with no global limit on the number of locked pages. What's keeping me from
creating 1000 of these things and locking down lots of RAM?
Thanks,
jon
next prev parent reply other threads:[~2020-02-12 21:10 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-30 16:23 [RFC PATCH] mm: extend memfd with ability to create "secret" memory areas Mike Rapoport
2020-02-06 18:51 ` Dave Hansen
2020-02-08 17:39 ` Mike Rapoport
2020-02-10 8:06 ` Reshetova, Elena
2020-02-11 19:52 ` Edgecombe, Rick P
2020-02-12 21:10 ` Jonathan Corbet [this message]
2020-02-16 6:46 ` Mike Rapoport
2020-08-14 17:46 ` Andy Lutomirski
2020-08-14 18:09 ` Dave Hansen
2020-08-26 16:54 ` Andy Lutomirski
2020-08-26 19:01 ` Florian Weimer
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