linux-kernel - Re: [PATCH v1 1/4] [RFC] fs/trampfd: Implement the trampoline file descriptor API

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Message-ID: <20200728145013.GA9972@redhat.com>
Date:   Tue, 28 Jul 2020 16:50:14 +0200
From:   Oleg Nesterov <oleg@...hat.com>
To:     madvenka@...ux.microsoft.com
Cc:     kernel-hardening@...ts.openwall.com, linux-api@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-fsdevel@...r.kernel.org, linux-integrity@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        linux-security-module@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCH v1 1/4] [RFC] fs/trampfd: Implement the trampoline file
 descriptor API

On 07/28, madvenka@...ux.microsoft.com wrote:
>
> +bool is_trampfd_vma(struct vm_area_struct *vma)
> +{
> +	struct file	*file = vma->vm_file;
> +
> +	if (!file)
> +		return false;
> +	return !strcmp(file->f_path.dentry->d_name.name, trampfd_name);

Hmm, this looks obviously wrong or I am totally confused. A user can
create a file named "[trampfd]", mmap it, and fool trampfd_fault() ?

Why not

	return file->f_op == trampfd_fops;

?

> +EXPORT_SYMBOL_GPL(is_trampfd_vma);

why is it exported?

Oleg.