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Subject[RFC PATCH 7/9] x86/sgx: Enforce noexec filesystem restriction for enclaves
Date
Do not allow an enclave page to be mapped with PROT_EXEC if the source
page is backed by a file on a noexec file system.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
---
arch/x86/kernel/cpu/sgx/driver/ioctl.c | 26 ++++++++++++++++++++++++--
1 file changed, 24 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/sgx/driver/ioctl.c b/arch/x86/kernel/cpu/sgx/driver/ioctl.c
index c30acd3fbbdd..5f71be7cbb01 100644
--- a/arch/x86/kernel/cpu/sgx/driver/ioctl.c
+++ b/arch/x86/kernel/cpu/sgx/driver/ioctl.c
@@ -576,6 +576,27 @@ static int __sgx_encl_add_page(struct sgx_encl *encl, unsigned long addr,
return ret;
}

+static int sgx_encl_page_protect(unsigned long src, unsigned long prot,
+ unsigned long *allowed_prot)
+{
+ struct vm_area_struct *vma;
+
+ if (!(*allowed_prot & VM_EXEC))
+ goto do_check;
+
+ down_read(&current->mm->mmap_sem);
+ vma = find_vma(current->mm, src);
+ if (!vma || (vma->vm_file && path_noexec(&vma->vm_file->f_path)))
+ *allowed_prot &= ~VM_EXEC;
+ up_read(&current->mm->mmap_sem);
+
+do_check:
+ if (prot & ~*allowed_prot)
+ return -EACCES;
+
+ return 0;
+}
+
static int sgx_encl_add_page(struct sgx_encl *encl, unsigned long addr,
unsigned long src, struct sgx_secinfo *secinfo,
unsigned int mrmask, unsigned int flags)
@@ -589,8 +610,9 @@ static int sgx_encl_add_page(struct sgx_encl *encl, unsigned long addr,
BUILD_BUG_ON(SGX_SECINFO_R != VM_READ || SGX_SECINFO_W != VM_WRITE ||
SGX_SECINFO_X != VM_EXEC);

- if (prot & ~allowed_prot)
- return -EACCES;
+ ret = sgx_encl_page_protect(src, prot, &allowed_prot);
+ if (ret)
+ return ret;

data_page = alloc_page(GFP_HIGHUSER);
if (!data_page)
--
2.21.0
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