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Date:   Tue, 28 Jan 2020 14:43:37 +0100
From:   Oleg Nesterov <oleg@redhat.com>
To:     Alexey Gladkov <gladkov.alexey@gmail.com>
Cc:     LKML <linux-kernel@vger.kernel.org>,
        Kernel Hardening <kernel-hardening@lists.openwall.com>,
        Linux API <linux-api@vger.kernel.org>,
        Linux FS Devel <linux-fsdevel@vger.kernel.org>,
        Linux Security Module <linux-security-module@vger.kernel.org>,
        Akinobu Mita <akinobu.mita@gmail.com>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Alexey Dobriyan <adobriyan@gmail.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Andy Lutomirski <luto@kernel.org>,
        Daniel Micay <danielmicay@gmail.com>,
        Djalal Harouni <tixxdz@gmail.com>,
        "Dmitry V . Levin" <ldv@altlinux.org>,
        "Eric W . Biederman" <ebiederm@xmission.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Ingo Molnar <mingo@kernel.org>,
        "J . Bruce Fields" <bfields@fieldses.org>,
        Jeff Layton <jlayton@poochiereds.net>,
        Jonathan Corbet <corbet@lwn.net>,
        Kees Cook <keescook@chromium.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Solar Designer <solar@openwall.com>,
        Stephen Rothwell <sfr@canb.auug.org.au>
Subject: Re: [PATCH v7 02/11] proc: add proc_fs_info struct to store proc
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Message-ID: <20200128134337.GC17943@redhat.com>
References: <20200125130541.450409-1-gladkov.alexey@gmail.com>
 <20200125130541.450409-3-gladkov.alexey@gmail.com>
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On 01/25, Alexey Gladkov wrote:
>
>  static int proc_init_fs_context(struct fs_context *fc)
>  {
>  	struct proc_fs_context *ctx;
> +	struct pid_namespace *pid_ns;
>
>  	ctx = kzalloc(sizeof(struct proc_fs_context), GFP_KERNEL);
>  	if (!ctx)
>  		return -ENOMEM;
>
> -	ctx->pid_ns = get_pid_ns(task_active_pid_ns(current));
> +	pid_ns = get_pid_ns(task_active_pid_ns(current));
> +
> +	if (!pid_ns->proc_mnt) {
> +		ctx->fs_info = kzalloc(sizeof(struct proc_fs_info), GFP_KERNEL);
> +		if (!ctx->fs_info) {
> +			kfree(ctx);
> +			return -ENOMEM;
> +		}
> +		ctx->fs_info->pid_ns = pid_ns;
> +	} else {
> +		ctx->fs_info = proc_sb_info(pid_ns->proc_mnt->mnt_sb);
> +	}
> +

it seems that this code lacks put_pid_ns() if pid_ns->proc_mnt != NULL
or if kzalloc() fails?

Or, better,

	pid_ns = task_active_pid_ns();

	if (!pid_ns->proc_mnt) {
		ctx->fs_info = kzalloc();
		...
		ctx->fs_info->pid_ns = get_pid_ns(pid_ns);
	}

No?

Oleg.