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KVM: SVM: Fix potential overflow in SEV's send|receive_update_data()

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KVM_SEV_SEND_UPDATE_DATA and KVM_SEV_RECEIVE_UPDATE_DATA have an integer
overflow issue. Params.guest_len and offset are both 32 bits wide, with a
large params.guest_len the check to confirm a page boundary is not
crossed can falsely pass:

    /* Check if we are crossing the page boundary *
    offset = params.guest_uaddr & (PAGE_SIZE - 1);
    if ((params.guest_len + offset > PAGE_SIZE))

Add an additional check to confirm that params.guest_len itself is not
greater than PAGE_SIZE.

Note, this isn't a security concern as overflow can happen if and only if
params.guest_len is greater than 0xfffff000, and the FW spec says these
commands fail with lengths greater than 16KB, i.e. the PSP will detect
KVM's goof.

Fixes: 15fb7de1a7 ("KVM: SVM: Add KVM_SEV_RECEIVE_UPDATE_DATA command")
Fixes: d3d1af85e2 ("KVM: SVM: Add KVM_SEND_UPDATE_DATA command")
Reported-by: Andy Nguyen <theflow@google.com>
Suggested-by: Thomas Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Peter Gonda <pgonda@google.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>
Cc: kvm@vger.kernel.org
Cc: stable@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Link: https://lore.kernel.org/r/20230207171354.4012821-1-pgonda@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Peter Gonda
2023-02-07 09:13:54 -08:00
committed by Sean Christopherson
parent 32e69f232d
commit f94f053aa3
1 changed files with 2 additions and 2 deletions
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4
arch/x86/kvm/svm/sev.c
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@@ -1294,7 +1294,7 @@ static int sev_send_update_data(struct kvm *kvm, struct kvm_sev_cmd *argp)
/* Check if we are crossing the page boundary */
offset = params.guest_uaddr & (PAGE_SIZE - 1);
if ((params.guest_len + offset > PAGE_SIZE))
if (params.guest_len > PAGE_SIZE || (params.guest_len + offset) > PAGE_SIZE)
return -EINVAL;
/* Pin guest memory */
@@ -1474,7 +1474,7 @@ static int sev_receive_update_data(struct kvm *kvm, struct kvm_sev_cmd *argp)
/* Check if we are crossing the page boundary */
offset = params.guest_uaddr & (PAGE_SIZE - 1);
if ((params.guest_len + offset > PAGE_SIZE))
if (params.guest_len > PAGE_SIZE || (params.guest_len + offset) > PAGE_SIZE)
return -EINVAL;
hdr = psp_copy_user_blob(params.hdr_uaddr, params.hdr_len);