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From: Greg KH <gregkh@linuxfoundation.org>
To: Matthew Garrett <matthewgarrett@google.com>
Cc: jmorris@namei.org, linux-security-module@vger.kernel.org,
	linux-kernel@vger.kernel.org, dhowells@redhat.com,
	linux-api@vger.kernel.org, luto@kernel.org,
	Matthew Garrett <mjg59@google.com>
Subject: Re: [PATCH V31 25/25] debugfs: Disable open() when kernel is locked down
Date: Wed, 27 Mar 2019 09:31:30 +0900	[thread overview]
Message-ID: <20190327003130.GB27311@kroah.com> (raw)
In-Reply-To: <20190326182742.16950-26-matthewgarrett@google.com>

On Tue, Mar 26, 2019 at 11:27:41AM -0700, Matthew Garrett wrote:
> From: Matthew Garrett <mjg59@google.com>
> 
> debugfs has not been meaningfully audited in terms of ensuring that
> userland cannot trample over the kernel. At Greg's request, disable
> access to it entirely when the kernel is locked down. This is done at
> open() time rather than init time as the kernel lockdown status may be
> made stricter at runtime.
> 
> Signed-off-by: Matthew Garrett <mjg59@google.com>
> Cc: gregkh@linuxfoundation.org
> ---
>  fs/debugfs/file.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c
> index 4fce1da7db23..9ae12ef29ba0 100644
> --- a/fs/debugfs/file.c
> +++ b/fs/debugfs/file.c
> @@ -142,6 +142,9 @@ static int open_proxy_open(struct inode *inode, struct file *filp)
>  	const struct file_operations *real_fops = NULL;
>  	int r;
>  
> +	if (kernel_is_locked_down("debugfs", LOCKDOWN_INTEGRITY))
> +		return -EPERM;

Why allow all this, why not just abort the registering of the filesystem
with the vfs core so it can't even be mounted?

thanks,

greg k-h

  parent reply	other threads:[~2019-03-27  0:31 UTC|newest]

Thread overview: 58+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-03-26 18:27 [PATCH V31 00/25] Add support for kernel lockdown Matthew Garrett
2019-03-26 18:27 ` [PATCH V31 01/25] Add the ability to lock down access to the running kernel image Matthew Garrett
2019-03-26 18:27 ` [PATCH V31 02/25] Enforce module signatures if the kernel is locked down Matthew Garrett
2019-03-26 18:27 ` [PATCH V31 03/25] Restrict /dev/{mem,kmem,port} when " Matthew Garrett
2019-03-26 18:27 ` [PATCH V31 04/25] kexec_load: Disable at runtime if " Matthew Garrett
2019-03-26 18:27 ` [PATCH V31 05/25] Copy secure_boot flag in boot params across kexec reboot Matthew Garrett
2019-03-26 18:27 ` [PATCH V31 06/25] kexec_file: split KEXEC_VERIFY_SIG into KEXEC_SIG and KEXEC_SIG_FORCE Matthew Garrett
2019-06-21  6:34   ` Dave Young
2019-06-21 20:13     ` Matthew Garrett
2019-06-21 20:14       ` Matthew Garrett
2019-03-26 18:27 ` [PATCH V31 07/25] kexec_file: Restrict at runtime if the kernel is locked down Matthew Garrett
2019-06-21  6:43   ` Dave Young
2019-06-21 20:18     ` Matthew Garrett
2019-06-24  1:52       ` Dave Young
2019-06-24 21:06         ` Matthew Garrett
2019-06-24 21:27           ` Mimi Zohar
2019-06-25  0:02             ` Matthew Garrett
2019-06-25  1:46               ` Mimi Zohar
2019-06-25  2:51           ` Dave Young
2019-03-26 18:27 ` [PATCH V31 08/25] hibernate: Disable when " Matthew Garrett
2019-03-26 18:27 ` [PATCH V31 09/25] uswsusp: " Matthew Garrett
2019-03-26 18:27 ` [PATCH V31 10/25] PCI: Lock down BAR access " Matthew Garrett
2019-03-26 20:55   ` Andy Lutomirski
2019-03-26 21:19     ` Alex Williamson
2019-03-26 18:27 ` [PATCH V31 11/25] x86: Lock down IO port " Matthew Garrett
2019-03-26 20:56   ` Andy Lutomirski
2019-03-26 18:27 ` [PATCH V31 12/25] x86/msr: Restrict MSR " Matthew Garrett
2019-03-26 18:27 ` [PATCH V31 13/25] ACPI: Limit access to custom_method " Matthew Garrett
2019-03-26 18:27 ` [PATCH V31 14/25] acpi: Ignore acpi_rsdp kernel param when the kernel has been " Matthew Garrett
2019-03-26 18:27 ` [PATCH V31 15/25] acpi: Disable ACPI table override if the kernel is " Matthew Garrett
2019-03-26 18:27 ` [PATCH V31 16/25] Prohibit PCMCIA CIS storage when " Matthew Garrett
2019-03-26 18:27 ` [PATCH V31 17/25] Lock down TIOCSSERIAL Matthew Garrett
2019-03-26 18:27 ` [PATCH V31 18/25] Lock down module params that specify hardware parameters (eg. ioport) Matthew Garrett
2019-03-26 18:27 ` [PATCH V31 19/25] x86/mmiotrace: Lock down the testmmiotrace module Matthew Garrett
2019-03-27 15:57   ` Steven Rostedt
2019-03-27 16:55     ` Matthew Garrett
2019-03-26 18:27 ` [PATCH V31 20/25] Lock down /proc/kcore Matthew Garrett
2019-03-26 18:27 ` [PATCH V31 21/25] Lock down kprobes when in confidentiality mode Matthew Garrett
2019-03-26 18:27 ` [PATCH V31 22/25] bpf: Restrict bpf when kernel lockdown is " Matthew Garrett
2019-03-26 19:21   ` Andy Lutomirski
2019-03-26 18:27 ` [PATCH V31 23/25] Lock down perf when " Matthew Garrett
2019-03-26 18:27 ` [PATCH V31 24/25] lockdown: Print current->comm in restriction messages Matthew Garrett
2019-03-26 18:27 ` [PATCH V31 25/25] debugfs: Disable open() when kernel is locked down Matthew Garrett
2019-03-26 19:20   ` Andy Lutomirski
2019-03-26 19:21     ` Matthew Garrett
2019-03-27  0:30     ` Greg KH
2019-03-27  4:29       ` Andy Lutomirski
2019-03-27  5:06         ` Greg KH
2019-03-27  5:29           ` Andy Lutomirski
2019-03-27  5:33             ` Greg KH
2019-03-27 16:53               ` James Morris
2019-03-27 17:39               ` Andy Lutomirski
2019-03-27 17:42                 ` Matthew Garrett
2019-03-27 18:29                   ` Greg KH
2019-03-27 18:31                 ` Greg KH
2019-03-27  0:31   ` Greg KH [this message]
2019-03-27  2:06     ` Matthew Garrett
2019-03-27  2:35       ` Greg KH

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