Commit 0bd0a4a1 authored by Thorsten Blum's avatar Thorsten Blum Committed by Sean Christopherson
Browse files

KVM: TDX: Replace kmalloc + copy_from_user with memdup_user in tdx_td_init() 



Use get_user() to retrieve the number of entries instead of allocating
memory for 'init_vm' with the maximum size, copying 'cmd->data' to it,
only to then read the actual entry count 'cpuid.nent' from the copy.

Use memdup_user() to allocate just enough memory to fit all entries and
to copy 'cmd->data' from userspace. Use struct_size() instead of
manually calculating the number of bytes to allocate and copy.

No functional changes intended.

Signed-off-by: default avatarThorsten Blum <thorsten.blum@linux.dev>
Link: https://lore.kernel.org/r/20250916213129.2535597-2-thorsten.blum@linux.dev


[sean: s/user_init_vm/user_data]
Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
parent f505c7b1

arch/x86/kvm/vmx/tdx.c

+10 −20
Original line number Diff line number Diff line
@@ -2749,9 +2749,11 @@ static int tdx_read_cpuid(struct kvm_vcpu *vcpu, u32 leaf, u32 sub_leaf, 


static int tdx_td_init(struct kvm *kvm, struct kvm_tdx_cmd *cmd)

{

	struct kvm_tdx_init_vm __user *user_data = u64_to_user_ptr(cmd->data);

	struct kvm_tdx *kvm_tdx = to_kvm_tdx(kvm);

	struct kvm_tdx_init_vm *init_vm;

	struct td_params *td_params = NULL;

	u32 nr_user_entries;

	int ret;



	BUILD_BUG_ON(sizeof(*init_vm) != 256 + sizeof_field(struct kvm_tdx_init_vm, cpuid));
@@ -2763,28 +2765,16 @@ static int tdx_td_init(struct kvm *kvm, struct kvm_tdx_cmd *cmd) 
	if (cmd->flags)

		return -EINVAL;



	init_vm = kmalloc(sizeof(*init_vm) +

			  sizeof(init_vm->cpuid.entries[0]) * KVM_MAX_CPUID_ENTRIES,

			  GFP_KERNEL);

	if (!init_vm)

		return -ENOMEM;



	if (copy_from_user(init_vm, u64_to_user_ptr(cmd->data), sizeof(*init_vm))) {

		ret = -EFAULT;

		goto out;

	}

	if (get_user(nr_user_entries, &user_data->cpuid.nent))

		return -EFAULT;



	if (init_vm->cpuid.nent > KVM_MAX_CPUID_ENTRIES) {

		ret = -E2BIG;

		goto out;

	}

	if (nr_user_entries > KVM_MAX_CPUID_ENTRIES)

		return -E2BIG;



	if (copy_from_user(init_vm->cpuid.entries,

			   u64_to_user_ptr(cmd->data) + sizeof(*init_vm),

			   flex_array_size(init_vm, cpuid.entries, init_vm->cpuid.nent))) {

		ret = -EFAULT;

		goto out;

	}

	init_vm = memdup_user(user_data,

			      struct_size(user_data, cpuid.entries, nr_user_entries));

	if (IS_ERR(init_vm))

		return PTR_ERR(init_vm);



	if (memchr_inv(init_vm->reserved, 0, sizeof(init_vm->reserved))) {

		ret = -EINVAL;