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
+ * permissions are *always* zero - the CPU ignores the user provided
+ * values and silently overwrites zero permissions.
+ */
if ((secinfo.flags & SGX_SECINFO_PAGE_TYPE_MASK) == SGX_SECINFO_TCS)
prot |= PROT_READ | PROT_WRITE;
--
2.20.1
