linux-kernel - [PATCH v2 0/7] KVM: selftests: Fix "fix hypercall test" build errors

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <20220928233652.783504-1-seanjc@google.com>
Date:   Wed, 28 Sep 2022 23:36:45 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     Tom Rix <trix@...hat.com>, kvm@...r.kernel.org,
        llvm@...ts.linux.dev, linux-kernel@...r.kernel.org,
        Andrew Jones <andrew.jones@...ux.dev>,
        Anup Patel <anup@...infault.org>,
        Atish Patra <atishp@...shpatra.org>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Janosch Frank <frankja@...ux.ibm.com>,
        Claudio Imbrenda <imbrenda@...ux.ibm.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Oliver Upton <oliver.upton@...ux.dev>,
        Jim Mattson <jmattson@...gle.com>
Subject: [PATCH v2 0/7] KVM: selftests: Fix "fix hypercall test" build errors

After a toolchain upgrade, the x86 fix_hypercall_test started throwing
warnings due to -Werror=array-bounds rightly complaining that the test is
generating an out-of-bounds array access.

The "obvious" fix is to replace the memcpy() with a memcmp() and compare
only the exact size of the hypercall instruction.  That worked, until I
fiddled with the code a bit more and suddenly the test started jumping into
the weeds due to gcc generating a call to the external memcmp() through the
PLT, which isn't supported in the selftests.

To fix that mess, which has been a pitfall for quite some time, provide
implementations of memcmp(), memcpy(), and memset() to effectively override
the compiler built-ins.  My thought is to start with the helpers that are
most likely to be used in guest code, and then add more as needed.

v2:
 - Revert a patch that avoided memset(). [Jim]
 - Collect reviews. [Oliver]
 - Rename kvm_string.c => string_overrides.c. [David]
 - Tweak the "fix hypercall" test to verify that the original opcode
   is preserved exactly. [Oliver]
 - Further dedup code in the "fix hypercall" test.

v1: https://lore.kernel.org/all/20220908233134.3523339-1-seanjc@google.com

Sean Christopherson (7):
  KVM: selftests: Implement memcmp(), memcpy(), and memset() for guest
    use
  KVM: selftests: Compare insn opcodes directly in fix_hypercall_test
  KVM: selftests: Remove unnecessary register shuffling in
    fix_hypercall_test
  KVM: selftests: Hardcode VMCALL/VMMCALL opcodes in "fix hypercall"
    test
  KVM: selftests: Explicitly verify KVM doesn't patch hypercall if
    quirk==off
  KVM: selftests: Dedup subtests of fix_hypercall_test
  Revert "KVM: selftests: Fix nested SVM tests when built with clang"

 tools/testing/selftests/kvm/Makefile          |  11 +-
 .../selftests/kvm/lib/string_override.c       |  39 +++++
 tools/testing/selftests/kvm/lib/x86_64/svm.c  |  14 +-
 .../selftests/kvm/x86_64/fix_hypercall_test.c | 134 +++++++-----------
 4 files changed, 103 insertions(+), 95 deletions(-)
 create mode 100644 tools/testing/selftests/kvm/lib/string_override.c


base-commit: c59fb127583869350256656b7ed848c398bef879
-- 
2.37.3.998.g577e59143f-goog