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-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <20221006003409.649993-6-seanjc@google.com>
Date:   Thu,  6 Oct 2022 00:34:07 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>, Shuah Khan <shuah@...nel.org>,
        Marc Zyngier <maz@...nel.org>,
        Anup Patel <anup@...infault.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Janosch Frank <frankja@...ux.ibm.com>,
        Claudio Imbrenda <imbrenda@...ux.ibm.com>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     James Morse <james.morse@....com>,
        Alexandru Elisei <alexandru.elisei@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Oliver Upton <oliver.upton@...ux.dev>,
        Atish Patra <atishp@...shpatra.org>,
        David Hildenbrand <david@...hat.com>,
        Tom Rix <trix@...hat.com>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, linux-kselftest@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev,
        kvmarm@...ts.cs.columbia.edu, kvm-riscv@...ts.infradead.org,
        linux-riscv@...ts.infradead.org, llvm@...ts.linux.dev,
        Colton Lewis <coltonlewis@...gle.com>,
        Andrew Jones <andrew.jones@...ux.dev>,
        Peter Gonda <pgonda@...gle.com>,
        Sean Christopherson <seanjc@...gle.com>
Subject: [PATCH v6 5/7] KVM: selftests: Make arm64's MMIO ucall multi-VM friendly

Fix a mostly-theoretical bug where ARM's ucall MMIO setup could result in
different VMs stomping on each other by cloberring the global pointer.

Fix the most obvious issue by saving the MMIO gpa into the VM.

A more subtle bug is that creating VMs in parallel (on multiple tasks)
could result in a VM using the wrong address.  Synchronizing a global to
a guest effectively snapshots the value on a per-VM basis, i.e. the
"global" is already prepped to work with multiple VMs, but setting the
global in the host is not thread-safe.  To fix that bug, add
write_guest_global() to allow stuffing a VM's copy of a "global" without
modifying the host value.

Reviewed-by: Andrew Jones <andrew.jones@...ux.dev>
Tested-by: Peter Gonda <pgonda@...gle.com>
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 .../selftests/kvm/include/kvm_util_base.h     | 15 +++++++++++++++
 .../testing/selftests/kvm/lib/aarch64/ucall.c | 19 ++++++++++++++-----
 2 files changed, 29 insertions(+), 5 deletions(-)

diff --git a/tools/testing/selftests/kvm/include/kvm_util_base.h b/tools/testing/selftests/kvm/include/kvm_util_base.h
index e42a09cd24a0..c14d531a942a 100644
--- a/tools/testing/selftests/kvm/include/kvm_util_base.h
+++ b/tools/testing/selftests/kvm/include/kvm_util_base.h
@@ -16,6 +16,7 @@
 #include <linux/kvm.h>
 #include "linux/rbtree.h"
 
+#include <asm/atomic.h>
 
 #include <sys/ioctl.h>
 
@@ -81,6 +82,7 @@ struct kvm_vm {
 	struct sparsebit *vpages_mapped;
 	bool has_irqchip;
 	bool pgd_created;
+	vm_paddr_t ucall_mmio_addr;
 	vm_paddr_t pgd;
 	vm_vaddr_t gdt;
 	vm_vaddr_t tss;
@@ -718,6 +720,19 @@ kvm_userspace_memory_region_find(struct kvm_vm *vm, uint64_t start,
 	memcpy(&(g), _p, sizeof(g));				\
 })
 
+/*
+ * Write a global value, but only in the VM's (guest's) domain.  Primarily used
+ * for "globals" that hold per-VM values (VMs always duplicate code and global
+ * data into their own region of physical memory), but can be used anytime it's
+ * undesirable to change the host's copy of the global.
+ */
+#define write_guest_global(vm, g, val) ({			\
+	typeof(g) *_p = addr_gva2hva(vm, (vm_vaddr_t)&(g));	\
+	typeof(g) _val = val;					\
+								\
+	memcpy(_p, &(_val), sizeof(g));				\
+})
+
 void assert_on_unhandled_exception(struct kvm_vcpu *vcpu);
 
 void vcpu_arch_dump(FILE *stream, struct kvm_vcpu *vcpu,
diff --git a/tools/testing/selftests/kvm/lib/aarch64/ucall.c b/tools/testing/selftests/kvm/lib/aarch64/ucall.c
index f02ae27c3e43..1c38bd260f90 100644
--- a/tools/testing/selftests/kvm/lib/aarch64/ucall.c
+++ b/tools/testing/selftests/kvm/lib/aarch64/ucall.c
@@ -6,20 +6,29 @@
  */
 #include "kvm_util.h"
 
+/*
+ * ucall_exit_mmio_addr holds per-VM values (global data is duplicated by each
+ * VM), it must not be accessed from host code.
+ */
 static vm_vaddr_t *ucall_exit_mmio_addr;
 
+static void ucall_set_mmio_addr(struct kvm_vm *vm, vm_paddr_t mmio_gpa)
+{
+	vm->ucall_mmio_addr = mmio_gpa;
+
+	write_guest_global(vm, ucall_exit_mmio_addr, (vm_vaddr_t *)mmio_gpa);
+}
+
 void ucall_arch_init(struct kvm_vm *vm, vm_paddr_t mmio_gpa)
 {
 	virt_pg_map(vm, mmio_gpa, mmio_gpa);
 
-	ucall_exit_mmio_addr = (vm_vaddr_t *)mmio_gpa;
-	sync_global_to_guest(vm, ucall_exit_mmio_addr);
+	ucall_set_mmio_addr(vm, mmio_gpa);
 }
 
 void ucall_arch_uninit(struct kvm_vm *vm)
 {
-	ucall_exit_mmio_addr = 0;
-	sync_global_to_guest(vm, ucall_exit_mmio_addr);
+	ucall_set_mmio_addr(vm, (vm_paddr_t)NULL);
 }
 
 void ucall_arch_do_ucall(vm_vaddr_t uc)
@@ -32,7 +41,7 @@ void *ucall_arch_get_ucall(struct kvm_vcpu *vcpu)
 	struct kvm_run *run = vcpu->run;
 
 	if (run->exit_reason == KVM_EXIT_MMIO &&
-	    run->mmio.phys_addr == (uint64_t)ucall_exit_mmio_addr) {
+	    run->mmio.phys_addr == vcpu->vm->ucall_mmio_addr) {
 		vm_vaddr_t gva;
 
 		TEST_ASSERT(run->mmio.is_write && run->mmio.len == 8,
-- 
2.38.0.rc1.362.ged0d419d3c-goog

Powered by blists - more mailing lists

Powered by Openwall GNU/*/Linux Powered by OpenVZ