From: Peter Gonda <pgonda@xxxxxxxxxx> commit f94f053aa3a5d6ff17951870483d9eb9e13de2e2 upstream. 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: 15fb7de1a7f5 ("KVM: SVM: Add KVM_SEV_RECEIVE_UPDATE_DATA command") Fixes: d3d1af85e2c7 ("KVM: SVM: Add KVM_SEND_UPDATE_DATA command") Reported-by: Andy Nguyen <theflow@xxxxxxxxxx> Suggested-by: Thomas Lendacky <thomas.lendacky@xxxxxxx> Signed-off-by: Peter Gonda <pgonda@xxxxxxxxxx> Cc: David Rientjes <rientjes@xxxxxxxxxx> Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx> Cc: Sean Christopherson <seanjc@xxxxxxxxxx> Cc: kvm@xxxxxxxxxxxxxxx Cc: stable@xxxxxxxxxxxxxxx Cc: linux-kernel@xxxxxxxxxxxxxxx Reviewed-by: Tom Lendacky <thomas.lendacky@xxxxxxx> Link: https://lore.kernel.org/r/20230207171354.4012821-1-pgonda@xxxxxxxxxx Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/x86/kvm/svm/sev.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/arch/x86/kvm/svm/sev.c +++ b/arch/x86/kvm/svm/sev.c @@ -1277,7 +1277,7 @@ static int sev_send_update_data(struct k /* 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 */ @@ -1457,7 +1457,7 @@ static int sev_receive_update_data(struc /* 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);