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From: Matthew Garrett <matthewgarrett@google.com>
To: jmorris@namei.org
Cc: linux-security-module@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-api@vger.kernel.org,
	David Howells <dhowells@redhat.com>,
	Alexei Starovoitov <alexei.starovoitov@gmail.com>,
	Matthew Garrett <mjg59@google.com>,
	Kees Cook <keescook@chromium.org>,
	netdev@vger.kernel.org, Chun-Yi Lee <jlee@suse.com>,
	Daniel Borkmann <daniel@iogearbox.net>
Subject: [PATCH V40 23/29] bpf: Restrict bpf when kernel lockdown is in confidentiality mode
Date: Mon, 19 Aug 2019 17:17:59 -0700
Message-ID: <20190820001805.241928-24-matthewgarrett@google.com> (raw)
In-Reply-To: <20190820001805.241928-1-matthewgarrett@google.com>

From: David Howells <dhowells@redhat.com>

bpf_read() and bpf_read_str() could potentially be abused to (eg) allow
private keys in kernel memory to be leaked. Disable them if the kernel
has been locked down in confidentiality mode.

Suggested-by: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Signed-off-by: Matthew Garrett <mjg59@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
cc: netdev@vger.kernel.org
cc: Chun-Yi Lee <jlee@suse.com>
cc: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: James Morris <jmorris@namei.org>
---
 include/linux/security.h     |  1 +
 kernel/trace/bpf_trace.c     | 10 ++++++++++
 security/lockdown/lockdown.c |  1 +
 3 files changed, 12 insertions(+)

diff --git a/include/linux/security.h b/include/linux/security.h
index 0b2529dbf0f4..e604f4c67f03 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -118,6 +118,7 @@ enum lockdown_reason {
 	LOCKDOWN_INTEGRITY_MAX,
 	LOCKDOWN_KCORE,
 	LOCKDOWN_KPROBES,
+	LOCKDOWN_BPF_READ,
 	LOCKDOWN_CONFIDENTIALITY_MAX,
 };
 
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 1c9a4745e596..33a954c367f3 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -139,8 +139,13 @@ BPF_CALL_3(bpf_probe_read, void *, dst, u32, size, const void *, unsafe_ptr)
 {
 	int ret;
 
+	ret = security_locked_down(LOCKDOWN_BPF_READ);
+	if (ret < 0)
+		goto out;
+
 	ret = probe_kernel_read(dst, unsafe_ptr, size);
 	if (unlikely(ret < 0))
+out:
 		memset(dst, 0, size);
 
 	return ret;
@@ -566,6 +571,10 @@ BPF_CALL_3(bpf_probe_read_str, void *, dst, u32, size,
 {
 	int ret;
 
+	ret = security_locked_down(LOCKDOWN_BPF_READ);
+	if (ret < 0)
+		goto out;
+
 	/*
 	 * The strncpy_from_unsafe() call will likely not fill the entire
 	 * buffer, but that's okay in this circumstance as we're probing
@@ -577,6 +586,7 @@ BPF_CALL_3(bpf_probe_read_str, void *, dst, u32, size,
 	 */
 	ret = strncpy_from_unsafe(dst, unsafe_ptr, size);
 	if (unlikely(ret < 0))
+out:
 		memset(dst, 0, size);
 
 	return ret;
diff --git a/security/lockdown/lockdown.c b/security/lockdown/lockdown.c
index 27b2cf51e443..2397772c56bd 100644
--- a/security/lockdown/lockdown.c
+++ b/security/lockdown/lockdown.c
@@ -33,6 +33,7 @@ static char *lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX+1] = {
 	[LOCKDOWN_INTEGRITY_MAX] = "integrity",
 	[LOCKDOWN_KCORE] = "/proc/kcore access",
 	[LOCKDOWN_KPROBES] = "use of kprobes",
+	[LOCKDOWN_BPF_READ] = "use of bpf to read kernel RAM",
 	[LOCKDOWN_CONFIDENTIALITY_MAX] = "confidentiality",
 };
 
-- 
2.23.0.rc1.153.gdeed80330f-goog


  parent reply index

Thread overview: 46+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-20  0:17 [PATCH V40 00/29] Add kernel lockdown functionality Matthew Garrett
2019-08-20  0:17 ` [PATCH V40 01/29] security: Support early LSMs Matthew Garrett
2019-08-20  0:17 ` [PATCH V40 02/29] security: Add a "locked down" LSM hook Matthew Garrett
2019-08-20  0:17 ` [PATCH V40 03/29] security: Add a static lockdown policy LSM Matthew Garrett
2019-08-20  0:17 ` [PATCH V40 04/29] lockdown: Enforce module signatures if the kernel is locked down Matthew Garrett
2019-08-20  0:17 ` [PATCH V40 05/29] lockdown: Restrict /dev/{mem,kmem,port} when " Matthew Garrett
2019-08-20  0:17 ` [PATCH V40 06/29] kexec_load: Disable at runtime if " Matthew Garrett
2019-08-20  0:17 ` [PATCH V40 07/29] lockdown: Copy secure_boot flag in boot params across kexec reboot Matthew Garrett
2019-08-20  0:17 ` [PATCH V40 08/29] kexec_file: split KEXEC_VERIFY_SIG into KEXEC_SIG and KEXEC_SIG_FORCE Matthew Garrett
2019-08-30 14:26   ` Philipp Rudo
2019-08-20  0:17 ` [PATCH V40 09/29] kexec_file: Restrict at runtime if the kernel is locked down Matthew Garrett
2019-08-20  0:17 ` [PATCH V40 10/29] hibernate: Disable when " Matthew Garrett
2019-08-20 21:43   ` Rafael J. Wysocki
2019-08-25  9:51   ` Pavel Machek
2019-08-20  0:17 ` [PATCH V40 11/29] PCI: Lock down BAR access " Matthew Garrett
2019-08-20 19:45   ` Bjorn Helgaas
2019-08-20 21:04     ` Matthew Garrett
2019-08-20  0:17 ` [PATCH V40 12/29] x86: Lock down IO port " Matthew Garrett
2019-08-20  0:17 ` [PATCH V40 13/29] x86/msr: Restrict MSR " Matthew Garrett
2019-08-20  0:17 ` [PATCH V40 14/29] ACPI: Limit access to custom_method " Matthew Garrett
2019-08-20 22:07   ` Rafael J. Wysocki
2019-08-20  0:17 ` [PATCH V40 15/29] acpi: Ignore acpi_rsdp kernel param when the kernel has been " Matthew Garrett
2019-08-20 22:08   ` Rafael J. Wysocki
2019-08-20  0:17 ` [PATCH V40 16/29] acpi: Disable ACPI table override if the kernel is " Matthew Garrett
2019-08-20 22:08   ` Rafael J. Wysocki
2019-08-20  0:17 ` [PATCH V40 17/29] lockdown: Prohibit PCMCIA CIS storage when " Matthew Garrett
2019-08-20  0:17 ` [PATCH V40 18/29] lockdown: Lock down TIOCSSERIAL Matthew Garrett
2019-08-20  0:17 ` [PATCH V40 19/29] lockdown: Lock down module params that specify hardware parameters (eg. ioport) Matthew Garrett
2019-08-20 16:39   ` Jessica Yu
2019-08-20  0:17 ` [PATCH V40 20/29] x86/mmiotrace: Lock down the testmmiotrace module Matthew Garrett
2019-08-20  0:17 ` [PATCH V40 21/29] lockdown: Lock down /proc/kcore Matthew Garrett
2019-08-20  0:17 ` [PATCH V40 22/29] lockdown: Lock down tracing and perf kprobes when in confidentiality mode Matthew Garrett
2019-08-20  0:17 ` Matthew Garrett [this message]
2019-08-20  0:18 ` [PATCH V40 24/29] lockdown: Lock down perf " Matthew Garrett
2019-08-20  0:18 ` [PATCH V40 25/29] kexec: Allow kexec_file() with appropriate IMA policy when locked down Matthew Garrett
2019-08-20  0:18 ` [PATCH V40 26/29] debugfs: Restrict debugfs when the kernel is " Matthew Garrett
2019-08-20  0:18 ` [PATCH V40 27/29] tracefs: Restrict tracefs " Matthew Garrett
2019-08-20  0:18 ` [PATCH V40 28/29] efi: Restrict efivar_ssdt_load " Matthew Garrett
2019-08-20  0:18 ` [PATCH V40 29/29] lockdown: Print current->comm in restriction messages Matthew Garrett
2019-08-20  6:45 ` [PATCH V40 00/29] Add kernel lockdown functionality James Morris
2019-08-30 16:28 ` [PATCH V40 03/29] security: Add a static lockdown policy LSM David Howells
2019-09-04 16:51   ` Matthew Garrett
2019-09-10 10:06     ` Matthew Garrett
2019-08-30 16:31 ` [PATCH V40 04/29] lockdown: Enforce module signatures if the kernel is locked down David Howells
2019-09-04 16:57   ` Matthew Garrett
2019-08-30 16:32 ` [PATCH V40 23/29] bpf: Restrict bpf when kernel lockdown is in confidentiality mode David Howells

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