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From: "Mickaël Salaün" <mic@digikod.net>
To: linux-kernel@vger.kernel.org
Cc: "Mickaël Salaün" <mic@digikod.net>,
	"Alexei Starovoitov" <ast@kernel.org>,
	"Andy Lutomirski" <luto@amacapital.net>,
	"Arnd Bergmann" <arnd@arndb.de>,
	"Casey Schaufler" <casey@schaufler-ca.com>,
	"Daniel Borkmann" <daniel@iogearbox.net>,
	"Daniel Mack" <daniel@zonque.org>,
	"David Drysdale" <drysdale@google.com>,
	"David S . Miller" <davem@davemloft.net>,
	"Elena Reshetova" <elena.reshetova@intel.com>,
	"Eric W . Biederman" <ebiederm@xmission.com>,
	"James Morris" <james.l.morris@oracle.com>,
	"Kees Cook" <keescook@chromium.org>,
	"Paul Moore" <pmoore@redhat.com>,
	"Sargun Dhillon" <sargun@sargun.me>,
	"Serge E . Hallyn" <serge@hallyn.com>,
	"Tejun Heo" <tj@kernel.org>, "Will Drewry" <wad@chromium.org>,
	kernel-hardening@lists.openwall.com, linux-api@vger.kernel.org,
	linux-security-module@vger.kernel.org, netdev@vger.kernel.org,
	cgroups@vger.kernel.org
Subject: [RFC v3 04/22] bpf: Set register type according to is_valid_access()
Date: Wed, 14 Sep 2016 09:23:57 +0200
Message-ID: <20160914072415.26021-5-mic@digikod.net> (raw)
In-Reply-To: <20160914072415.26021-1-mic@digikod.net>

This fix a pointer leak when an unprivileged eBPF program read a pointer
value from the context. Even if is_valid_access() returns a pointer
type, the eBPF verifier replace it with UNKNOWN_VALUE. The register
value containing an address is then allowed to leak. Moreover, this
prevented unprivileged eBPF programs to use functions with (legitimate)
pointer arguments.

This bug was not a problem until now because the only unprivileged eBPF
program allowed is of type BPF_PROG_TYPE_SOCKET_FILTER and all the types
from its context are UNKNOWN_VALUE.

Signed-off-by: Mickaël Salaün <mic@digikod.net>
Fixes: 969bf05eb3ce ("bpf: direct packet access")
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
---
 kernel/bpf/verifier.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index c0c4a92dae8c..608cbffb0e86 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -794,10 +794,8 @@ static int check_mem_access(struct verifier_env *env, u32 regno, int off,
 		}
 		err = check_ctx_access(env, off, size, t, &reg_type);
 		if (!err && t == BPF_READ && value_regno >= 0) {
-			mark_reg_unknown_value(state->regs, value_regno);
-			if (env->allow_ptr_leaks)
-				/* note that reg.[id|off|range] == 0 */
-				state->regs[value_regno].type = reg_type;
+			/* note that reg.[id|off|range] == 0 */
+			state->regs[value_regno].type = reg_type;
 		}
 
 	} else if (reg->type == FRAME_PTR || reg->type == PTR_TO_STACK) {
-- 
2.9.3

  parent reply index

Thread overview: 76+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-09-14  7:23 [RFC v3 00/22] Landlock LSM: Unprivileged sandboxing Mickaël Salaün
2016-09-14  7:23 ` [RFC v3 01/22] landlock: Add Kconfig Mickaël Salaün
2016-09-14  7:23 ` [RFC v3 02/22] bpf: Move u64_to_ptr() to BPF headers and inline it Mickaël Salaün
2016-09-14  7:23 ` [RFC v3 03/22] bpf,landlock: Add a new arraymap type to deal with (Landlock) handles Mickaël Salaün
2016-09-14 18:51   ` Alexei Starovoitov
2016-09-14 23:22     ` Mickaël Salaün
2016-09-14 23:28       ` Alexei Starovoitov
2016-09-15 21:51         ` Mickaël Salaün
2016-10-03 23:53   ` Kees Cook
2016-10-05 22:02     ` Mickaël Salaün
2016-09-14  7:23 ` Mickaël Salaün [this message]
2016-10-19 14:54   ` [RFC v3 04/22] bpf: Set register type according to is_valid_access() Thomas Graf
2016-10-19 15:10     ` Daniel Borkmann
2016-09-14  7:23 ` [RFC v3 05/22] bpf,landlock: Add eBPF program subtype and is_valid_subtype() verifier Mickaël Salaün
2016-10-19 15:01   ` Thomas Graf
2016-09-14  7:23 ` [RFC v3 06/22] landlock: Add LSM hooks Mickaël Salaün
2016-10-19 15:19   ` Thomas Graf
2016-10-19 22:42     ` Mickaël Salaün
2016-09-14  7:24 ` [RFC v3 07/22] landlock: Handle file comparisons Mickaël Salaün
2016-09-14 19:07   ` Jann Horn
2016-09-14 22:39     ` Mickaël Salaün
2016-09-14 21:06   ` Alexei Starovoitov
2016-09-14 23:02     ` Mickaël Salaün
2016-09-14 23:24       ` Alexei Starovoitov
2016-09-15 21:25         ` Mickaël Salaün
2016-09-20  0:12           ` lsm naming dilemma. " Alexei Starovoitov
2016-09-20  1:10             ` Sargun Dhillon
2016-09-20 16:58               ` Mickaël Salaün
2016-10-03 23:30   ` Kees Cook
2016-09-14  7:24 ` [RFC v3 08/22] seccomp: Fix documentation for struct seccomp_filter Mickaël Salaün
2016-09-14  7:24 ` [RFC v3 09/22] seccomp: Move struct seccomp_filter in seccomp.h Mickaël Salaün
2016-09-14  7:24 ` [RFC v3 10/22] seccomp: Split put_seccomp_filter() with put_seccomp() Mickaël Salaün
2016-09-14  7:24 ` [RFC v3 11/22] seccomp,landlock: Handle Landlock hooks per process hierarchy Mickaël Salaün
2016-09-14 18:43   ` Andy Lutomirski
2016-09-14 22:34     ` Mickaël Salaün
2016-10-03 23:52       ` Kees Cook
2016-10-05 21:05         ` Mickaël Salaün
2016-09-14  7:24 ` [RFC v3 12/22] bpf: Cosmetic change for bpf_prog_attach() Mickaël Salaün
2016-09-14  7:24 ` [RFC v3 13/22] bpf/cgroup: Replace struct bpf_prog with union bpf_object Mickaël Salaün
2016-09-14  7:24 ` [RFC v3 14/22] bpf/cgroup: Make cgroup_bpf_update() return an error code Mickaël Salaün
2016-09-14 21:16   ` Alexei Starovoitov
2016-09-14  7:24 ` [RFC v3 15/22] bpf/cgroup: Move capability check Mickaël Salaün
2016-09-14  7:24 ` [RFC v3 16/22] bpf/cgroup,landlock: Handle Landlock hooks per cgroup Mickaël Salaün
2016-10-03 23:43   ` Kees Cook
2016-10-05 20:58     ` Mickaël Salaün
2016-10-05 21:25       ` Kees Cook
2016-09-14  7:24 ` [RFC v3 17/22] cgroup: Add access check for cgroup_get_from_fd() Mickaël Salaün
2016-09-14 22:06   ` Mickaël Salaün
2016-09-14  7:24 ` [RFC v3 18/22] cgroup,landlock: Add CGRP_NO_NEW_PRIVS to handle unprivileged hooks Mickaël Salaün
2016-09-14 18:27   ` Andy Lutomirski
2016-09-14 22:11     ` Mickaël Salaün
2016-09-15  1:25       ` Andy Lutomirski
2016-09-15  2:19         ` Alexei Starovoitov
2016-09-15  2:27           ` Andy Lutomirski
2016-09-15  4:00             ` Alexei Starovoitov
2016-09-15  4:08               ` Andy Lutomirski
2016-09-15  4:31                 ` Alexei Starovoitov
2016-09-15  4:38                   ` Andy Lutomirski
2016-09-15  4:48                     ` Alexei Starovoitov
2016-09-15 19:41                       ` Mickaël Salaün
2016-09-20  4:37                         ` Sargun Dhillon
2016-09-20 17:02                           ` Mickaël Salaün
2016-09-15 19:35         ` Mickaël Salaün
2016-09-14  7:24 ` [RFC v3 19/22] landlock: Add interrupted origin Mickaël Salaün
2016-09-14 18:29   ` Andy Lutomirski
2016-09-14 22:14     ` Mickaël Salaün
2016-09-15  1:19       ` Andy Lutomirski
2016-10-03 23:46         ` Kees Cook
2016-10-05 21:01           ` Mickaël Salaün
2016-09-14  7:24 ` [RFC v3 20/22] landlock: Add update and debug access flags Mickaël Salaün
2016-09-14  7:24 ` [RFC v3 21/22] bpf,landlock: Add optional skb pointer in the Landlock context Mickaël Salaün
2016-09-14 21:20   ` Alexei Starovoitov
2016-09-14 22:46     ` Mickaël Salaün
2016-09-14  7:24 ` [RFC v3 22/22] samples/landlock: Add sandbox example Mickaël Salaün
2016-09-14 21:24   ` Alexei Starovoitov
2016-09-14 14:36 ` [RFC v3 00/22] Landlock LSM: Unprivileged sandboxing David Laight

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