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From: Vasily Gorbik <gor@linux.ibm.com>
To: Matthew Garrett <matthewgarrett@google.com>
Cc: jmorris@namei.org, linux-security-module@vger.kernel.org,
	linux-kernel@vger.kernel.org, dhowells@redhat.com
Subject: Re: [PATCH 26/27] debugfs: Restrict debugfs when the kernel is locked down
Date: Thu, 25 Apr 2019 12:49:14 +0200
Message-ID: <your-ad-here.call-01556189354-ext-1943@work.hours> (raw)
In-Reply-To: <20190306235913.6631-27-matthewgarrett@google.com>

On Wed, Mar 06, 2019 at 03:59:12PM -0800, Matthew Garrett wrote:
> From: David Howells <dhowells@redhat.com>
> 
>  static int open_proxy_open(struct inode *inode, struct file *filp)
>  {
>  	struct dentry *dentry = F_DENTRY(filp);
> @@ -147,6 +166,11 @@ static int open_proxy_open(struct inode *inode, struct file *filp)
>  		return r == -EIO ? -ENOENT : r;
>  
>  	real_fops = debugfs_real_fops(filp);
> +
> +	r = -EPERM;
> +	if (debugfs_is_locked_down(inode, filp, real_fops))
> +		goto out;
> +
>  	real_fops = fops_get(real_fops);
>  	if (!real_fops) {
>  		/* Huh? Module did not clean up after itself at exit? */
> @@ -272,6 +296,10 @@ static int full_proxy_open(struct inode *inode, struct file *filp)
>  		return r == -EIO ? -ENOENT : r;
>  
>  	real_fops = debugfs_real_fops(filp);
> +	r = -EPERM;
> +	if (debugfs_is_locked_down(inode, filp, real_fops))
> +		goto out;
> +
>  	real_fops = fops_get(real_fops);
>  	if (!real_fops) {
>  		/* Huh? Module did not cleanup after itself at exit? */

Please be aware that this patch has been known to cause problems in
distributions which picked this patch series already:
ubuntu:
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1807686
fedora:
https://bugzilla.redhat.com/show_bug.cgi?id=1658675
as well as rhel 8.

I've sent around this potential fix which has been picked by the
distributions (offered via bugzillas), but went apparently unnoticed
at lkml:
https://lkml.org/lkml/2018/11/21/634
https://lkml.org/lkml/2018/11/21/635

"""
With "debugfs: Restrict debugfs when the kernel is locked down"
return code "r" is unconditionally set to -EPERM, which stays like that
until function return if no "open" file operation defined, effectivelly
resulting in "Operation not permitted" for all such files despite kernel
lock down status or CONFIG_LOCK_DOWN_KERNEL being enabled.
"""

I would appreciate if you consider that change, possibly just
squashing into yours.


  reply index

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-03-06 23:58 [PULL REQUEST] Kernel lockdown patches for 5.2 Matthew Garrett
2019-03-06 23:58 ` [PATCH 01/27] Add the ability to lock down access to the running kernel image Matthew Garrett
2019-03-06 23:58 ` [PATCH 02/27] Add a SysRq option to lift kernel lockdown Matthew Garrett
2019-03-07  0:09   ` Randy Dunlap
2019-03-07  0:12     ` Matthew Garrett
2019-03-06 23:58 ` [PATCH 03/27] Enforce module signatures if the kernel is locked down Matthew Garrett
2019-03-08 23:00   ` James Morris
2019-03-08 23:30     ` Matthew Garrett
2019-03-09  4:45       ` James Morris
2019-03-06 23:58 ` [PATCH 04/27] Restrict /dev/{mem,kmem,port} when " Matthew Garrett
2019-03-06 23:58 ` [PATCH 05/27] kexec_load: Disable at runtime if " Matthew Garrett
2019-03-06 23:58 ` [PATCH 06/27] Copy secure_boot flag in boot params across kexec reboot Matthew Garrett
2019-03-06 23:58 ` [PATCH 07/27] kexec_file: split KEXEC_VERIFY_SIG into KEXEC_SIG and KEXEC_SIG_FORCE Matthew Garrett
2019-03-06 23:58 ` [PATCH 08/27] kexec_file: Restrict at runtime if the kernel is locked down Matthew Garrett
2019-03-06 23:58 ` [PATCH 09/27] hibernate: Disable when " Matthew Garrett
2019-03-07 14:55   ` Alan Cox
2019-03-07 17:32     ` Matthew Garrett
2019-03-18 18:55       ` Alan Cox
2019-03-06 23:58 ` [PATCH 10/27] uswsusp: " Matthew Garrett
2019-03-06 23:58 ` [PATCH 11/27] PCI: Lock down BAR access " Matthew Garrett
2019-03-06 23:58 ` [PATCH 12/27] x86: Lock down IO port " Matthew Garrett
2019-03-06 23:58 ` [PATCH 13/27] x86/msr: Restrict MSR " Matthew Garrett
2019-03-06 23:59 ` [PATCH 14/27] ACPI: Limit access to custom_method " Matthew Garrett
2019-03-06 23:59 ` [PATCH 15/27] acpi: Ignore acpi_rsdp kernel param when the kernel has been " Matthew Garrett
2019-03-06 23:59 ` [PATCH 16/27] acpi: Disable ACPI table override if the kernel is " Matthew Garrett
2019-03-06 23:59 ` [PATCH 17/27] acpi: Disable APEI error injection " Matthew Garrett
2019-03-06 23:59 ` [PATCH 18/27] Prohibit PCMCIA CIS storage when " Matthew Garrett
2019-03-06 23:59 ` [PATCH 19/27] Lock down TIOCSSERIAL Matthew Garrett
2019-03-06 23:59 ` [PATCH 20/27] Lock down module params that specify hardware parameters (eg. ioport) Matthew Garrett
2019-03-06 23:59 ` [PATCH 21/27] x86/mmiotrace: Lock down the testmmiotrace module Matthew Garrett
2019-03-06 23:59 ` [PATCH 22/27] Lock down /proc/kcore Matthew Garrett
2019-03-06 23:59 ` [PATCH 23/27] Lock down kprobes Matthew Garrett
2019-03-06 23:59 ` [PATCH 24/27] bpf: Restrict kernel image access functions when the kernel is locked down Matthew Garrett
2019-03-06 23:59 ` [PATCH 25/27] Lock down perf Matthew Garrett
2019-03-06 23:59 ` [PATCH 26/27] debugfs: Restrict debugfs when the kernel is locked down Matthew Garrett
2019-04-25 10:49   ` Vasily Gorbik [this message]
2019-04-25 21:44     ` Matthew Garrett
2019-03-06 23:59 ` [PATCH 27/27] lockdown: Print current->comm in restriction messages Matthew Garrett
2019-03-07  3:56 ` [PULL REQUEST] Kernel lockdown patches for 5.2 Mimi Zohar
2019-03-07  4:24   ` Matthew Garrett
2019-03-12  0:42     ` Matthew Garrett
2019-03-12  1:52       ` Mimi Zohar
2019-03-07 15:59 ` [PATCH 02/27] Add a SysRq option to lift kernel lockdown David Howells
  -- strict thread matches above, loose matches on Subject: below --
2019-02-28 21:28 [PULL REQUEST] Lock down patches Matthew Garrett
2019-02-28 23:11 ` [PATCH 01/27] Add the ability to lock down access to the running kernel image Matthew Garrett
2019-02-28 23:12   ` [PATCH 26/27] debugfs: Restrict debugfs when the kernel is locked down Matthew Garrett

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