2018-01-06 14:13:39 +00:00
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From 9327cee21ebe7ca7a82c27c209e1fa3ac3d23232 Mon Sep 17 00:00:00 2001
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From: Ben Hutchings <ben@decadent.org.uk>
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Date: Thu, 4 Jan 2018 08:01:23 -0600
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2018-01-08 09:25:09 +00:00
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Subject: [PATCH 228/241] UBUNTU: SAUCE: bpf/verifier: Fix states_equal()
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2018-01-06 14:13:39 +00:00
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comparison of pointer and UNKNOWN
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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An UNKNOWN_VALUE is not supposed to be derived from a pointer, unless
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pointer leaks are allowed. Therefore, states_equal() must not treat
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a state with a pointer in a register as "equal" to a state with an
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UNKNOWN_VALUE in that register.
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This was fixed differently upstream, but the code around here was
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largely rewritten in 4.14 by commit f1174f77b50c "bpf/verifier: rework
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value tracking". The bug can be detected by the bpf/verifier sub-test
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"pointer/scalar confusion in state equality check (way 1)".
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Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
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Cc: Edward Cree <ecree@solarflare.com>
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Cc: Jann Horn <jannh@google.com>
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Cc: Alexei Starovoitov <ast@kernel.org>
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CVE-2017-17864
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Link: https://anonscm.debian.org/cgit/kernel/linux.git/tree/debian/patches/bugfix/all/bpf-verifier-fix-states_equal-comparison-of-pointer-and-unknown.patch?h=stretch-security
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Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
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Signed-off-by: Andy Whitcroft <apw@canonical.com>
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Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
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(cherry picked from commit 3fb4378083def9b22f6ae222e75d880fc5c59048)
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Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
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---
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kernel/bpf/verifier.c | 5 +++--
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1 file changed, 3 insertions(+), 2 deletions(-)
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diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
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index cdfa07a4ef27..4ecb2e10c5e0 100644
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--- a/kernel/bpf/verifier.c
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+++ b/kernel/bpf/verifier.c
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@@ -2980,11 +2980,12 @@ static bool states_equal(struct bpf_verifier_env *env,
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/* If we didn't map access then again we don't care about the
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* mismatched range values and it's ok if our old type was
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- * UNKNOWN and we didn't go to a NOT_INIT'ed reg.
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+ * UNKNOWN and we didn't go to a NOT_INIT'ed or pointer reg.
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*/
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if (rold->type == NOT_INIT ||
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(!varlen_map_access && rold->type == UNKNOWN_VALUE &&
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- rcur->type != NOT_INIT))
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+ rcur->type != NOT_INIT &&
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+ !__is_pointer_value(env->allow_ptr_leaks, rcur)))
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continue;
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/* Don't care about the reg->id in this case. */
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--
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2.14.2
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