[PATCH 08/34] KVM: Introduce KVM_SET_USER_MEMORY_REGION2
Paolo Bonzini
pbonzini at redhat.com
Sun Nov 5 08:30:11 PST 2023
From: Sean Christopherson <seanjc at google.com>
Introduce a "version 2" of KVM_SET_USER_MEMORY_REGION so that additional
information can be supplied without setting userspace up to fail. The
padding in the new kvm_userspace_memory_region2 structure will be used to
pass a file descriptor in addition to the userspace_addr, i.e. allow
userspace to point at a file descriptor and map memory into a guest that
is NOT mapped into host userspace.
Alternatively, KVM could simply add "struct kvm_userspace_memory_region2"
without a new ioctl(), but as Paolo pointed out, adding a new ioctl()
makes detection of bad flags a bit more robust, e.g. if the new fd field
is guarded only by a flag and not a new ioctl(), then a userspace bug
(setting a "bad" flag) would generate out-of-bounds access instead of an
-EINVAL error.
Cc: Jarkko Sakkinen <jarkko at kernel.org>
Reviewed-by: Paolo Bonzini <pbonzini at redhat.com>
Reviewed-by: Xiaoyao Li <xiaoyao.li at intel.com>
Signed-off-by: Sean Christopherson <seanjc at google.com>
Reviewed-by: Fuad Tabba <tabba at google.com>
Tested-by: Fuad Tabba <tabba at google.com>
Message-Id: <20231027182217.3615211-9-seanjc at google.com>
Signed-off-by: Paolo Bonzini <pbonzini at redhat.com>
---
Documentation/virt/kvm/api.rst | 22 +++++++++++++
arch/x86/kvm/x86.c | 2 +-
include/linux/kvm_host.h | 4 +--
include/uapi/linux/kvm.h | 13 ++++++++
virt/kvm/kvm_main.c | 57 +++++++++++++++++++++++++++++-----
5 files changed, 87 insertions(+), 11 deletions(-)
diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index 7025b3751027..bdea1423c5f8 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -1340,6 +1340,7 @@ yet and must be cleared on entry.
__u64 guest_phys_addr;
__u64 memory_size; /* bytes */
__u64 userspace_addr; /* start of the userspace allocated memory */
+ __u64 pad[16];
};
/* for kvm_userspace_memory_region::flags */
@@ -6192,6 +6193,27 @@ to know what fields can be changed for the system register described by
``op0, op1, crn, crm, op2``. KVM rejects ID register values that describe a
superset of the features supported by the system.
+4.140 KVM_SET_USER_MEMORY_REGION2
+---------------------------------
+
+:Capability: KVM_CAP_USER_MEMORY2
+:Architectures: all
+:Type: vm ioctl
+:Parameters: struct kvm_userspace_memory_region2 (in)
+:Returns: 0 on success, -1 on error
+
+::
+
+ struct kvm_userspace_memory_region2 {
+ __u32 slot;
+ __u32 flags;
+ __u64 guest_phys_addr;
+ __u64 memory_size; /* bytes */
+ __u64 userspace_addr; /* start of the userspace allocated memory */
+ };
+
+See KVM_SET_USER_MEMORY_REGION.
+
5. The kvm_run structure
========================
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 2c924075f6f1..7b389f27dffc 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -12576,7 +12576,7 @@ void __user * __x86_set_memory_region(struct kvm *kvm, int id, gpa_t gpa,
}
for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++) {
- struct kvm_userspace_memory_region m;
+ struct kvm_userspace_memory_region2 m;
m.slot = id | (i << 16);
m.flags = 0;
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 5faba69403ac..4e741ff27af3 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -1146,9 +1146,9 @@ enum kvm_mr_change {
};
int kvm_set_memory_region(struct kvm *kvm,
- const struct kvm_userspace_memory_region *mem);
+ const struct kvm_userspace_memory_region2 *mem);
int __kvm_set_memory_region(struct kvm *kvm,
- const struct kvm_userspace_memory_region *mem);
+ const struct kvm_userspace_memory_region2 *mem);
void kvm_arch_free_memslot(struct kvm *kvm, struct kvm_memory_slot *slot);
void kvm_arch_memslots_updated(struct kvm *kvm, u64 gen);
int kvm_arch_prepare_memory_region(struct kvm *kvm,
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 211b86de35ac..308cc70bd6ab 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -95,6 +95,16 @@ struct kvm_userspace_memory_region {
__u64 userspace_addr; /* start of the userspace allocated memory */
};
+/* for KVM_SET_USER_MEMORY_REGION2 */
+struct kvm_userspace_memory_region2 {
+ __u32 slot;
+ __u32 flags;
+ __u64 guest_phys_addr;
+ __u64 memory_size;
+ __u64 userspace_addr;
+ __u64 pad[16];
+};
+
/*
* The bit 0 ~ bit 15 of kvm_userspace_memory_region::flags are visible for
* userspace, other bits are reserved for kvm internal use which are defined
@@ -1201,6 +1211,7 @@ struct kvm_ppc_resize_hpt {
#define KVM_CAP_ARM_EAGER_SPLIT_CHUNK_SIZE 228
#define KVM_CAP_ARM_SUPPORTED_BLOCK_SIZES 229
#define KVM_CAP_ARM_SUPPORTED_REG_MASK_RANGES 230
+#define KVM_CAP_USER_MEMORY2 231
#ifdef KVM_CAP_IRQ_ROUTING
@@ -1483,6 +1494,8 @@ struct kvm_vfio_spapr_tce {
struct kvm_userspace_memory_region)
#define KVM_SET_TSS_ADDR _IO(KVMIO, 0x47)
#define KVM_SET_IDENTITY_MAP_ADDR _IOW(KVMIO, 0x48, __u64)
+#define KVM_SET_USER_MEMORY_REGION2 _IOW(KVMIO, 0x49, \
+ struct kvm_userspace_memory_region2)
/* enable ucontrol for s390 */
struct kvm_s390_ucas_mapping {
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index dc81279ea385..756b94ecd511 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1580,7 +1580,15 @@ static void kvm_replace_memslot(struct kvm *kvm,
}
}
-static int check_memory_region_flags(const struct kvm_userspace_memory_region *mem)
+/*
+ * Flags that do not access any of the extra space of struct
+ * kvm_userspace_memory_region2. KVM_SET_USER_MEMORY_REGION_V1_FLAGS
+ * only allows these.
+ */
+#define KVM_SET_USER_MEMORY_REGION_V1_FLAGS \
+ (KVM_MEM_LOG_DIRTY_PAGES | KVM_MEM_READONLY)
+
+static int check_memory_region_flags(const struct kvm_userspace_memory_region2 *mem)
{
u32 valid_flags = KVM_MEM_LOG_DIRTY_PAGES;
@@ -1982,7 +1990,7 @@ static bool kvm_check_memslot_overlap(struct kvm_memslots *slots, int id,
* Must be called holding kvm->slots_lock for write.
*/
int __kvm_set_memory_region(struct kvm *kvm,
- const struct kvm_userspace_memory_region *mem)
+ const struct kvm_userspace_memory_region2 *mem)
{
struct kvm_memory_slot *old, *new;
struct kvm_memslots *slots;
@@ -2086,7 +2094,7 @@ int __kvm_set_memory_region(struct kvm *kvm,
EXPORT_SYMBOL_GPL(__kvm_set_memory_region);
int kvm_set_memory_region(struct kvm *kvm,
- const struct kvm_userspace_memory_region *mem)
+ const struct kvm_userspace_memory_region2 *mem)
{
int r;
@@ -2098,7 +2106,7 @@ int kvm_set_memory_region(struct kvm *kvm,
EXPORT_SYMBOL_GPL(kvm_set_memory_region);
static int kvm_vm_ioctl_set_memory_region(struct kvm *kvm,
- struct kvm_userspace_memory_region *mem)
+ struct kvm_userspace_memory_region2 *mem)
{
if ((u16)mem->slot >= KVM_USER_MEM_SLOTS)
return -EINVAL;
@@ -4568,6 +4576,7 @@ static int kvm_vm_ioctl_check_extension_generic(struct kvm *kvm, long arg)
{
switch (arg) {
case KVM_CAP_USER_MEMORY:
+ case KVM_CAP_USER_MEMORY2:
case KVM_CAP_DESTROY_MEMORY_REGION_WORKS:
case KVM_CAP_JOIN_MEMORY_REGIONS_WORKS:
case KVM_CAP_INTERNAL_ERROR_DATA:
@@ -4823,6 +4832,14 @@ static int kvm_vm_ioctl_get_stats_fd(struct kvm *kvm)
return fd;
}
+#define SANITY_CHECK_MEM_REGION_FIELD(field) \
+do { \
+ BUILD_BUG_ON(offsetof(struct kvm_userspace_memory_region, field) != \
+ offsetof(struct kvm_userspace_memory_region2, field)); \
+ BUILD_BUG_ON(sizeof_field(struct kvm_userspace_memory_region, field) != \
+ sizeof_field(struct kvm_userspace_memory_region2, field)); \
+} while (0)
+
static long kvm_vm_ioctl(struct file *filp,
unsigned int ioctl, unsigned long arg)
{
@@ -4845,15 +4862,39 @@ static long kvm_vm_ioctl(struct file *filp,
r = kvm_vm_ioctl_enable_cap_generic(kvm, &cap);
break;
}
+ case KVM_SET_USER_MEMORY_REGION2:
case KVM_SET_USER_MEMORY_REGION: {
- struct kvm_userspace_memory_region kvm_userspace_mem;
+ struct kvm_userspace_memory_region2 mem;
+ unsigned long size;
+
+ if (ioctl == KVM_SET_USER_MEMORY_REGION) {
+ /*
+ * Fields beyond struct kvm_userspace_memory_region shouldn't be
+ * accessed, but avoid leaking kernel memory in case of a bug.
+ */
+ memset(&mem, 0, sizeof(mem));
+ size = sizeof(struct kvm_userspace_memory_region);
+ } else {
+ size = sizeof(struct kvm_userspace_memory_region2);
+ }
+
+ /* Ensure the common parts of the two structs are identical. */
+ SANITY_CHECK_MEM_REGION_FIELD(slot);
+ SANITY_CHECK_MEM_REGION_FIELD(flags);
+ SANITY_CHECK_MEM_REGION_FIELD(guest_phys_addr);
+ SANITY_CHECK_MEM_REGION_FIELD(memory_size);
+ SANITY_CHECK_MEM_REGION_FIELD(userspace_addr);
r = -EFAULT;
- if (copy_from_user(&kvm_userspace_mem, argp,
- sizeof(kvm_userspace_mem)))
+ if (copy_from_user(&mem, argp, size))
goto out;
- r = kvm_vm_ioctl_set_memory_region(kvm, &kvm_userspace_mem);
+ r = -EINVAL;
+ if (ioctl == KVM_SET_USER_MEMORY_REGION &&
+ (mem.flags & ~KVM_SET_USER_MEMORY_REGION_V1_FLAGS))
+ goto out;
+
+ r = kvm_vm_ioctl_set_memory_region(kvm, &mem);
break;
}
case KVM_GET_DIRTY_LOG: {
--
2.39.1
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