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KVM: TDX: Use struct_size to simplify tdx_get_capabilities()

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Use struct_size() instead of manually calculating the number of bytes to
allocate for 'caps', including the nested flexible array, and copy all of
'caps' to user space with a single copy_to_user() call (thanks to the full
size being provided by struct_size()).

Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
Tested-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Link: https://patch.msgid.link/20251017213914.167301-1-thorsten.blum@linux.dev
[sean: separate from swap of get_user() vs. kzalloc() ordering]
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Sean Christopherson
2025-11-10 13:24:53 -08:00
parent 11b79f8318
commit 398180f93c
1 changed files with 4 additions and 9 deletions
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13
arch/x86/kvm/vmx/tdx.c
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@@ -2231,9 +2231,8 @@ static int tdx_get_capabilities(struct kvm_tdx_cmd *cmd)
if (nr_user_entries < td_conf->num_cpuid_config)
return -E2BIG;
caps = kzalloc(sizeof(*caps) +
sizeof(struct kvm_cpuid_entry2) * td_conf->num_cpuid_config,
GFP_KERNEL);
caps = kzalloc(struct_size(caps, cpuid.entries,
td_conf->num_cpuid_config), GFP_KERNEL);
if (!caps)
return -ENOMEM;
@@ -2241,16 +2240,12 @@ static int tdx_get_capabilities(struct kvm_tdx_cmd *cmd)
if (ret)
goto out;
if (copy_to_user(user_caps, caps, sizeof(*caps))) {
if (copy_to_user(user_caps, caps, struct_size(caps, cpuid.entries,
caps->cpuid.nent))) {
ret = -EFAULT;
goto out;
}
if (copy_to_user(user_caps->cpuid.entries, caps->cpuid.entries,
caps->cpuid.nent *
sizeof(caps->cpuid.entries[0])))
ret = -EFAULT;
out:
/* kfree() accepts NULL. */
kfree(caps);