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authorPaolo Bonzini <pbonzini@redhat.com>2023-04-21 19:19:02 -0400
committerPaolo Bonzini <pbonzini@redhat.com>2023-04-21 19:19:02 -0400
commit265b97cbc22e0f67f79a71443b60dc1237ca5ee6 (patch)
treefb42627096d8efe1e76a482a66cc13fac76e7ca4 /arch
parent0bf9601f8ef0703523018e975d6c1f3fdfcff4b9 (diff)
parenta25bc8486f9c01c1af6b6c5657234b2eee2c39d6 (diff)
Merge tag 'kvmarm-fixes-6.3-4' of git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm into HEAD
KVM/arm64 fixes for 6.3, part #4 - Plug a buffer overflow due to the use of the user-provided register width for firmware regs. Outright reject accesses where the user register width does not match the kernel representation. - Protect non-atomic RMW operations on vCPU flags against preemption, as an update to the flags by an intervening preemption could be lost.
Diffstat (limited to 'arch')
-rw-r--r--arch/arm64/include/asm/kvm_host.h19
-rw-r--r--arch/arm64/kvm/hypercalls.c2
2 files changed, 20 insertions, 1 deletions
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index bcd774d74f34..3dd691c85ca0 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -576,9 +576,22 @@ struct kvm_vcpu_arch {
({ \
__build_check_flag(v, flagset, f, m); \
\
- v->arch.flagset & (m); \
+ READ_ONCE(v->arch.flagset) & (m); \
})
+/*
+ * Note that the set/clear accessors must be preempt-safe in order to
+ * avoid nesting them with load/put which also manipulate flags...
+ */
+#ifdef __KVM_NVHE_HYPERVISOR__
+/* the nVHE hypervisor is always non-preemptible */
+#define __vcpu_flags_preempt_disable()
+#define __vcpu_flags_preempt_enable()
+#else
+#define __vcpu_flags_preempt_disable() preempt_disable()
+#define __vcpu_flags_preempt_enable() preempt_enable()
+#endif
+
#define __vcpu_set_flag(v, flagset, f, m) \
do { \
typeof(v->arch.flagset) *fset; \
@@ -586,9 +599,11 @@ struct kvm_vcpu_arch {
__build_check_flag(v, flagset, f, m); \
\
fset = &v->arch.flagset; \
+ __vcpu_flags_preempt_disable(); \
if (HWEIGHT(m) > 1) \
*fset &= ~(m); \
*fset |= (f); \
+ __vcpu_flags_preempt_enable(); \
} while (0)
#define __vcpu_clear_flag(v, flagset, f, m) \
@@ -598,7 +613,9 @@ struct kvm_vcpu_arch {
__build_check_flag(v, flagset, f, m); \
\
fset = &v->arch.flagset; \
+ __vcpu_flags_preempt_disable(); \
*fset &= ~(m); \
+ __vcpu_flags_preempt_enable(); \
} while (0)
#define vcpu_get_flag(v, ...) __vcpu_get_flag((v), __VA_ARGS__)
diff --git a/arch/arm64/kvm/hypercalls.c b/arch/arm64/kvm/hypercalls.c
index 5da884e11337..c4b4678bc4a4 100644
--- a/arch/arm64/kvm/hypercalls.c
+++ b/arch/arm64/kvm/hypercalls.c
@@ -397,6 +397,8 @@ int kvm_arm_set_fw_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
u64 val;
int wa_level;
+ if (KVM_REG_SIZE(reg->id) != sizeof(val))
+ return -ENOENT;
if (copy_from_user(&val, uaddr, KVM_REG_SIZE(reg->id)))
return -EFAULT;