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From: KP Singh <kpsingh@chromium.org>
To: linux-kernel@vger.kernel.org, bpf@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 KaFai Lau" <kafai@fb.com>,
	"Song Liu" <songliubraving@fb.com>, "Yonghong Song" <yhs@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: [RFC v1 07/14] krsi: Check for premissions on eBPF attachment
Date: Tue, 10 Sep 2019 13:55:20 +0200
Message-ID: <20190910115527.5235-8-kpsingh@chromium.org> (raw)
In-Reply-To: <20190910115527.5235-1-kpsingh@chromium.org>

From: KP Singh <kpsingh@google.com>

Add validation checks for the attachment of eBPF programs.

The following permissions are required:

- CAP_SYS_ADMIN to load eBPF programs
- CAP_MAC_ADMIN (to update the policy of an LSM)
- The securityfs file being a KRSI hook and writable (O_RDWR)

Signed-off-by: KP Singh <kpsingh@google.com>
---
 security/krsi/ops.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/security/krsi/ops.c b/security/krsi/ops.c
index cf4d06189aa1..a61508b7018f 100644
--- a/security/krsi/ops.c
+++ b/security/krsi/ops.c
@@ -23,11 +23,31 @@ static struct krsi_hook *get_hook_from_fd(int fd)
 		goto error;
 	}
 
+	/*
+	 * Only CAP_MAC_ADMIN users are allowed to make
+	 * changes to LSM hooks
+	 */
+	if (!capable(CAP_MAC_ADMIN)) {
+		ret = -EPERM;
+		goto error;
+	}
+
 	if (!is_krsi_hook_file(f.file)) {
 		ret = -EINVAL;
 		goto error;
 	}
 
+	/*
+	 * It's wrong to attach the program to the hook
+	 * if the file is not opened for a write. Note that,
+	 * this is an EBADF and not an EPERM because the file
+	 * has been opened with an incorrect mode.
+	 */
+	if (!(f.file->f_mode & FMODE_WRITE)) {
+		ret = -EBADF;
+		goto error;
+	}
+
 	/*
 	 * The securityfs dentry never disappears, so we don't need to take a
 	 * reference to it.
-- 
2.20.1


  parent 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
2019-09-10 11:55 ` KP Singh [this message]
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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