On Mon, Aug 19, 2019 at 06:25:40PM +0300, Jarkko Sakkinen wrote:
> The way permissions are managed inside the driver is not trivial and
> intuitive. The non-obvious parts were not properly remarked in the
> source code. This patch refines them a bit.
>
> Cc: Sean Christopherson <sean.j.christpherson@xxxxxxxxx>
> Cc: Shay Katz-zamir <shay.katz-zamir@xxxxxxxxx>
> Cc: Serge Ayoun <serge.ayoun@xxxxxxxxx>
> Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx>
> ---
> arch/x86/kernel/cpu/sgx/driver/ioctl.c | 9 ++++++++-
> 1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/kernel/cpu/sgx/driver/ioctl.c b/arch/x86/kernel/cpu/sgx/driver/ioctl.c
> index 9b784a061a47..64d3286f3324 100644
> --- a/arch/x86/kernel/cpu/sgx/driver/ioctl.c
> +++ b/arch/x86/kernel/cpu/sgx/driver/ioctl.c
> @@ -259,7 +259,10 @@ static struct sgx_encl_page *sgx_encl_page_alloc(struct sgx_encl *encl,
> return ERR_PTR(-ENOMEM);
> encl_page->desc = addr;
> encl_page->encl = encl;
> +
> + /* Calculate maximum of the VM flags for the page. */
> encl_page->vm_prot_bits = calc_vm_prot_bits(prot, 0);
> +
> ret = radix_tree_insert(&encl->page_tree, PFN_DOWN(encl_page->desc),
> encl_page);
> if (ret) {
> @@ -640,11 +643,15 @@ static long sgx_ioc_enclave_add_page(struct file *filep, void __user *arg)
>
> data = kmap(data_page);
>
> + /* Set prot bits matching to the SECINFO permissions. */
> prot = _calc_vm_trans(secinfo.flags, SGX_SECINFO_R, PROT_READ) |
> _calc_vm_trans(secinfo.flags, SGX_SECINFO_W, PROT_WRITE) |
> _calc_vm_trans(secinfo.flags, SGX_SECINFO_X, PROT_EXEC);
>
> - /* TCS pages need to be RW in the PTEs, but can be 0 in the EPCM. */
> + /* TCS pages must always RW set for CPU access while the SECINFO
Should be
/*
* TCS pages ...
> + * permissions are *always* zero - the CPU ignores the user provided
> + * values and silently overwrites zero permissions.
Maybe 'overwrites with zero permissions'?
> + */
> if ((secinfo.flags & SGX_SECINFO_PAGE_TYPE_MASK) == SGX_SECINFO_TCS)
> prot |= PROT_READ | PROT_WRITE;
>
> --
> 2.20.1
>
