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From: Yonghong Song <yhs@fb.com>
To: KP Singh <kpsingh@chromium.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"bpf@vger.kernel.org" <bpf@vger.kernel.org>,
	"linux-security-module@vger.kernel.org" 
	<linux-security-module@vger.kernel.org>
Cc: "Alexei Starovoitov" <ast@kernel.org>,
	"Daniel Borkmann" <daniel@iogearbox.net>,
	"James Morris" <jmorris@namei.org>,
	"Kees Cook" <keescook@chromium.org>,
	"Thomas Garnier" <thgarnie@chromium.org>,
	"Michael Halcrow" <mhalcrow@google.com>,
	"Paul Turner" <pjt@google.com>,
	"Brendan Gregg" <brendan.d.gregg@gmail.com>,
	"Jann Horn" <jannh@google.com>,
	"Matthew Garrett" <mjg59@google.com>,
	"Christian Brauner" <christian@brauner.io>,
	"Mickaël Salaün" <mic@digikod.net>,
	"Florent Revest" <revest@chromium.org>,
	"Martin Lau" <kafai@fb.com>, "Song Liu" <songliubraving@fb.com>,
	"Serge E. Hallyn" <serge@hallyn.com>,
	"Mauro Carvalho Chehab" <mchehab+samsung@kernel.org>,
	"David S. Miller" <davem@davemloft.net>,
	"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
	"Nicolas Ferre" <nicolas.ferre@microchip.com>,
	"Stanislav Fomichev" <sdf@google.com>,
	"Quentin Monnet" <quentin.monnet@netronome.com>,
	"Andrey Ignatov" <rdna@fb.com>, "Joe Stringer" <joe@wand.net.nz>
Subject: Re: Re: [RFC v1 06/14] krsi: Implement eBPF operations, attachment and execution
Date: Sun, 15 Sep 2019 00:37:29 +0000
Message-ID: <f2732b46-d4d1-c811-dd6b-ad0ef280513f@fb.com> (raw)
In-Reply-To: <bb2d4453-f01f-8fb2-d901-a7a0a5eb4a4d@fb.com>



On 9/14/19 5:56 PM, Yonghong Song wrote:
> 
> 
> On 9/10/19 12:55 PM, KP Singh wrote:
>> From: KP Singh <kpsingh@google.com>
>>
>> A user space program can attach an eBPF program by:
>>
>>     hook_fd = open("/sys/kernel/security/krsi/process_execution", O_RDWR)
>>     prog_fd = bpf(BPF_PROG_LOAD, ...)
>>     bpf(BPF_PROG_ATTACH, hook_fd, prog_fd)
>>
>> When such an attach call is received, the attachment logic looks up the
>> dentry and appends the program to the bpf_prog_array.
>>
>> The BPF programs are stored in a bpf_prog_array and writes to the array
>> are guarded by a mutex. The eBPF programs are executed as a part of the
>> LSM hook they are attached to. If any of the eBPF programs return
>> an error (-ENOPERM) the action represented by the hook is denied.
>>
>> Signed-off-by: KP Singh <kpsingh@google.com>
>> ---
>>    include/linux/krsi.h              |  18 ++++++
>>    kernel/bpf/syscall.c              |   3 +-
>>    security/krsi/include/krsi_init.h |  51 +++++++++++++++
>>    security/krsi/krsi.c              |  13 +++-
>>    security/krsi/krsi_fs.c           |  28 ++++++++
>>    security/krsi/ops.c               | 102 ++++++++++++++++++++++++++++++
>>    6 files changed, 213 insertions(+), 2 deletions(-)
>>    create mode 100644 include/linux/krsi.h
>>
[...]
>>    
>> +static inline int krsi_run_progs(enum krsi_hook_type t, struct krsi_ctx *ctx)
>> +{
>> +	struct bpf_prog_array_item *item;
>> +	struct bpf_prog *prog;
>> +	struct krsi_hook *h = &krsi_hooks_list[t];
>> +	int ret, retval = 0;
> 
> Reverse christmas tree style?
> 
>> +
>> +	preempt_disable();
> 
> Do we need preempt_disable() here?

 From the following patches, I see perf_event_output() helper
and per-cpu array usage. So, indeed preempt_disable() is needed.

> 
>> +	rcu_read_lock();
>> +
>> +	item = rcu_dereference(h->progs)->items;
>> +	while ((prog = READ_ONCE(item->prog))) {
>> +		ret = BPF_PROG_RUN(prog, ctx);
>> +		if (ret < 0) {
>> +			retval = ret;
>> +			goto out;
>> +		}
>> +		item++;
>> +	}
>> +
>> +out:
>> +	rcu_read_unlock();
>> +	preempt_enable();
>> +	return IS_ENABLED(CONFIG_SECURITY_KRSI_ENFORCE) ? retval : 0;
>> +}
>> +
[...]

  reply index

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-10 11:55 [RFC v1 00/14] Kernel Runtime Security Instrumentation KP Singh
2019-09-10 11:55 ` [RFC v1 01/14] krsi: Add a skeleton and config options for the KRSI LSM KP Singh
2019-09-10 11:55 ` [RFC v1 02/14] krsi: Introduce types for KRSI eBPF KP Singh
2019-09-10 11:55 ` [RFC v1 03/14] bpf: krsi: sync BPF UAPI header with tools KP Singh
2019-09-10 11:55 ` [RFC v1 04/14] krsi: Add support in libbpf for BPF_PROG_TYPE_KRSI KP Singh
2019-09-14 16:09   ` Yonghong Song
2019-09-10 11:55 ` [RFC v1 05/14] krsi: Initialize KRSI hooks and create files in securityfs KP Singh
2019-09-14 16:26   ` Yonghong Song
2019-09-10 11:55 ` [RFC v1 06/14] krsi: Implement eBPF operations, attachment and execution KP Singh
2019-09-14 16:56   ` Yonghong Song
2019-09-15  0:37     ` Yonghong Song [this message]
2019-09-10 11:55 ` [RFC v1 07/14] krsi: Check for premissions on eBPF attachment KP Singh
2019-09-10 11:55 ` [RFC v1 08/14] krsi: Show attached program names in hook read handler KP Singh
2019-09-10 11:55 ` [RFC v1 09/14] krsi: Add a helper function for bpf_perf_event_output KP Singh
2019-09-14 18:23   ` Yonghong Song
2019-09-10 11:55 ` [RFC v1 10/14] krsi: Handle attachment of the same program KP Singh
2019-09-10 11:55 ` [RFC v1 11/14] krsi: Pin argument pages in bprm_check_security hook KP Singh
2019-09-10 11:55 ` [RFC v1 12/14] krsi: Add an eBPF helper function to get the value of an env variable KP Singh
2019-09-15  0:16   ` Yonghong Song
2019-09-16 13:00     ` KP Singh
2019-09-17 16:58       ` Yonghong Song
2019-09-17 19:36         ` KP Singh
2019-09-10 11:55 ` [RFC v1 13/14] krsi: Provide an example to read and log environment variables KP Singh
2019-09-15  0:24   ` Yonghong Song
2019-09-10 11:55 ` [RFC v1 14/14] krsi: Pin arg pages only when needed KP Singh
2019-09-15  0:33   ` Yonghong Song
2019-09-15  1:40     ` KP Singh
2019-09-15 19:45       ` Yonghong Song

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