From 20bad055e2d74e4d02b593d8fb38bd915394dceb Mon Sep 17 00:00:00 2001 From: Salvatore Bonaccorso Date: Sun, 7 Oct 2018 08:29:33 +0200 Subject: [PATCH] [arm64] KVM: Tighten guest core register access from userspace (CVE-2018-18021) --- debian/changelog | 5 + ...n-guest-core-register-access-from-us.patch | 99 +++++++++++++++++++ debian/patches/series | 1 + 3 files changed, 105 insertions(+) create mode 100644 debian/patches/bugfix/arm64/arm64-kvm-tighten-guest-core-register-access-from-us.patch diff --git a/debian/changelog b/debian/changelog index afb10498b..3344fe2c8 100644 --- a/debian/changelog +++ b/debian/changelog @@ -1,7 +1,12 @@ linux (4.18.10-2) UNRELEASED; urgency=medium + [ Ben Hutchings ] * [rt][arm64,armhf] Fix build failure after rebasing onto 4.18.10 + [ Salvatore Bonaccorso ] + * [arm64] KVM: Tighten guest core register access from userspace + (CVE-2018-18021) + -- Ben Hutchings Fri, 05 Oct 2018 18:09:26 +0100 linux (4.18.10-1) unstable; urgency=medium diff --git a/debian/patches/bugfix/arm64/arm64-kvm-tighten-guest-core-register-access-from-us.patch b/debian/patches/bugfix/arm64/arm64-kvm-tighten-guest-core-register-access-from-us.patch new file mode 100644 index 000000000..df5b5a548 --- /dev/null +++ b/debian/patches/bugfix/arm64/arm64-kvm-tighten-guest-core-register-access-from-us.patch @@ -0,0 +1,99 @@ +From: Dave Martin +Date: Thu, 27 Sep 2018 16:53:21 +0100 +Subject: arm64: KVM: Tighten guest core register access from userspace +Origin: https://git.kernel.org/linus/d26c25a9d19b5976b319af528886f89cf455692d +Bug-Debian-Security: https://security-tracker.debian.org/tracker/CVE-2018-18021 + +We currently allow userspace to access the core register file +in about any possible way, including straddling multiple +registers and doing unaligned accesses. + +This is not the expected use of the ABI, and nobody is actually +using it that way. Let's tighten it by explicitly checking +the size and alignment for each field of the register file. + +Cc: +Fixes: 2f4a07c5f9fe ("arm64: KVM: guest one-reg interface") +Reviewed-by: Christoffer Dall +Reviewed-by: Mark Rutland +Signed-off-by: Dave Martin +[maz: rewrote Dave's initial patch to be more easily backported] +Signed-off-by: Marc Zyngier +Signed-off-by: Will Deacon +--- + arch/arm64/kvm/guest.c | 45 +++++++++++++++++++++++++++++++++++++++++++++ + 1 file changed, 45 insertions(+) + +diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c +index 07256b08226c..3088463bafc1 100644 +--- a/arch/arm64/kvm/guest.c ++++ b/arch/arm64/kvm/guest.c +@@ -57,6 +57,45 @@ static u64 core_reg_offset_from_id(u64 id) + return id & ~(KVM_REG_ARCH_MASK | KVM_REG_SIZE_MASK | KVM_REG_ARM_CORE); + } + ++static int validate_core_offset(const struct kvm_one_reg *reg) ++{ ++ u64 off = core_reg_offset_from_id(reg->id); ++ int size; ++ ++ switch (off) { ++ case KVM_REG_ARM_CORE_REG(regs.regs[0]) ... ++ KVM_REG_ARM_CORE_REG(regs.regs[30]): ++ case KVM_REG_ARM_CORE_REG(regs.sp): ++ case KVM_REG_ARM_CORE_REG(regs.pc): ++ case KVM_REG_ARM_CORE_REG(regs.pstate): ++ case KVM_REG_ARM_CORE_REG(sp_el1): ++ case KVM_REG_ARM_CORE_REG(elr_el1): ++ case KVM_REG_ARM_CORE_REG(spsr[0]) ... ++ KVM_REG_ARM_CORE_REG(spsr[KVM_NR_SPSR - 1]): ++ size = sizeof(__u64); ++ break; ++ ++ case KVM_REG_ARM_CORE_REG(fp_regs.vregs[0]) ... ++ KVM_REG_ARM_CORE_REG(fp_regs.vregs[31]): ++ size = sizeof(__uint128_t); ++ break; ++ ++ case KVM_REG_ARM_CORE_REG(fp_regs.fpsr): ++ case KVM_REG_ARM_CORE_REG(fp_regs.fpcr): ++ size = sizeof(__u32); ++ break; ++ ++ default: ++ return -EINVAL; ++ } ++ ++ if (KVM_REG_SIZE(reg->id) == size && ++ IS_ALIGNED(off, size / sizeof(__u32))) ++ return 0; ++ ++ return -EINVAL; ++} ++ + static int get_core_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg) + { + /* +@@ -76,6 +115,9 @@ static int get_core_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg) + (off + (KVM_REG_SIZE(reg->id) / sizeof(__u32))) >= nr_regs) + return -ENOENT; + ++ if (validate_core_offset(reg)) ++ return -EINVAL; ++ + if (copy_to_user(uaddr, ((u32 *)regs) + off, KVM_REG_SIZE(reg->id))) + return -EFAULT; + +@@ -98,6 +140,9 @@ static int set_core_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg) + (off + (KVM_REG_SIZE(reg->id) / sizeof(__u32))) >= nr_regs) + return -ENOENT; + ++ if (validate_core_offset(reg)) ++ return -EINVAL; ++ + if (KVM_REG_SIZE(reg->id) > sizeof(tmp)) + return -EINVAL; + +-- +2.11.0 + diff --git a/debian/patches/series b/debian/patches/series index 695f27d1b..def369bd9 100644 --- a/debian/patches/series +++ b/debian/patches/series @@ -145,6 +145,7 @@ bugfix/all/Revert-net-increase-fragment-memory-usage-limits.patch bugfix/all/floppy-Do-not-copy-a-kernel-pointer-to-user-memory-i.patch bugfix/all/scsi-target-iscsi-Use-hex2bin-instead-of-a-re-implem.patch bugfix/all/scsi-target-iscsi-Use-bin2hex-instead-of-a-re-implem.patch +bugfix/arm64/arm64-kvm-tighten-guest-core-register-access-from-us.patch # Fix exported symbol versions bugfix/all/module-disable-matching-missing-version-crc.patch