patches/kernel/0228-UBUNTU-SAUCE-bpf-verifier-Fix-states_equal-compariso.patch

   1 From 9327cee21ebe7ca7a82c27c209e1fa3ac3d23232 Mon Sep 17 00:00:00 2001
   2 From: Ben Hutchings <ben@decadent.org.uk>
   3 Date: Thu, 4 Jan 2018 08:01:23 -0600
   4 Subject: [PATCH 228/233] UBUNTU: SAUCE: bpf/verifier: Fix states_equal()
   5  comparison of pointer and UNKNOWN
   6 MIME-Version: 1.0
   7 Content-Type: text/plain; charset=UTF-8
   8 Content-Transfer-Encoding: 8bit
   9
  10 An UNKNOWN_VALUE is not supposed to be derived from a pointer, unless
  11 pointer leaks are allowed.  Therefore, states_equal() must not treat
  12 a state with a pointer in a register as "equal" to a state with an
  13 UNKNOWN_VALUE in that register.
  14
  15 This was fixed differently upstream, but the code around here was
  16 largely rewritten in 4.14 by commit f1174f77b50c "bpf/verifier: rework
  17 value tracking".  The bug can be detected by the bpf/verifier sub-test
  18 "pointer/scalar confusion in state equality check (way 1)".
  19
  20 Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
  21 Cc: Edward Cree <ecree@solarflare.com>
  22 Cc: Jann Horn <jannh@google.com>
  23 Cc: Alexei Starovoitov <ast@kernel.org>
  24 CVE-2017-17864
  25 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
  26 Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
  27 Signed-off-by: Andy Whitcroft <apw@canonical.com>
  28 Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
  29 (cherry picked from commit 3fb4378083def9b22f6ae222e75d880fc5c59048)
  30 Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
  31 ---
  32  kernel/bpf/verifier.c | 5 +++--
  33  1 file changed, 3 insertions(+), 2 deletions(-)
  34
  35 diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
  36 index cdfa07a4ef27..4ecb2e10c5e0 100644
  37 --- a/kernel/bpf/verifier.c
  38 +++ b/kernel/bpf/verifier.c
  39 @@ -2980,11 +2980,12 @@ static bool states_equal(struct bpf_verifier_env *env,
  40
  41                 /* If we didn't map access then again we don't care about the
  42                  * mismatched range values and it's ok if our old type was
  43 -                * UNKNOWN and we didn't go to a NOT_INIT'ed reg.
  44 +                * UNKNOWN and we didn't go to a NOT_INIT'ed or pointer reg.
  45                  */
  46                 if (rold->type == NOT_INIT ||
  47                     (!varlen_map_access && rold->type == UNKNOWN_VALUE &&
  48 -                    rcur->type != NOT_INIT))
  49 +                    rcur->type != NOT_INIT &&
  50 +                    !__is_pointer_value(env->allow_ptr_leaks, rcur)))
  51                         continue;
  52
  53                 /* Don't care about the reg->id in this case. */
  54 --
  55 2.14.2
  56