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Date: Wed, 5 Jun 2019 19:11:43 -0700
From: Sean Christopherson <sean.j.christopherson@...el.com>
To: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Cc: Andy Lutomirski <luto@...nel.org>,
Cedric Xing <cedric.xing@...el.com>,
Stephen Smalley <sds@...ho.nsa.gov>,
James Morris <jmorris@...ei.org>,
"Serge E . Hallyn" <serge@...lyn.com>,
LSM List <linux-security-module@...r.kernel.org>,
Paul Moore <paul@...l-moore.com>,
Eric Paris <eparis@...isplace.org>, selinux@...r.kernel.org,
Jethro Beekman <jethro@...tanix.com>,
Dave Hansen <dave.hansen@...el.com>,
Thomas Gleixner <tglx@...utronix.de>,
Linus Torvalds <torvalds@...ux-foundation.org>,
LKML <linux-kernel@...r.kernel.org>, X86 ML <x86@...nel.org>,
linux-sgx@...r.kernel.org,
Andrew Morton <akpm@...ux-foundation.org>, nhorman@...hat.com,
npmccallum@...hat.com, Serge Ayoun <serge.ayoun@...el.com>,
Shay Katz-zamir <shay.katz-zamir@...el.com>,
Haitao Huang <haitao.huang@...el.com>,
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
Kai Svahn <kai.svahn@...el.com>,
Borislav Petkov <bp@...en8.de>,
Josh Triplett <josh@...htriplett.org>,
Kai Huang <kai.huang@...el.com>,
David Rientjes <rientjes@...gle.com>,
William Roberts <william.c.roberts@...el.com>,
Philip Tricca <philip.b.tricca@...el.com>
Subject: [RFC PATCH v2 3/5] x86/sgx: Enforce noexec filesystem restriction for enclaves
Do not allow an enclave page to be mapped with PROT_EXEC if the source
vma does not have VM_MAYEXEC. This effectively enforces noexec as
do_mmap() clears VM_MAYEXEC if the vma is being loaded from a noexec
path, i.e. prevents executing a file by loading it into an enclave.
Checking noexec indirectly by way of VM_MAYEXEC naturally handles any
other cases that clear VM_MAYEXEC to deny execute permissions.
Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
---
arch/x86/kernel/cpu/sgx/driver/ioctl.c | 47 +++++++++++++++++++++++---
1 file changed, 42 insertions(+), 5 deletions(-)
diff --git a/arch/x86/kernel/cpu/sgx/driver/ioctl.c b/arch/x86/kernel/cpu/sgx/driver/ioctl.c
index ef5c2ce0f37b..44b2d73de7c3 100644
--- a/arch/x86/kernel/cpu/sgx/driver/ioctl.c
+++ b/arch/x86/kernel/cpu/sgx/driver/ioctl.c
@@ -577,6 +577,44 @@ static int sgx_encl_add_page(struct sgx_encl *encl, unsigned long addr,
return ret;
}
+static int sgx_encl_page_copy(void *dst, unsigned long src, unsigned long prot)
+{
+ struct vm_area_struct *vma;
+ int ret;
+
+ if (!(prot & VM_EXEC))
+ return 0;
+
+ /* Hold mmap_sem across copy_from_user() to avoid a TOCTOU race. */
+ down_read(¤t->mm->mmap_sem);
+
+ vma = find_vma(current->mm, src);
+ if (!vma) {
+ ret = -EFAULT;
+ goto out;
+ }
+
+ /*
+ * Query VM_MAYEXEC as an indirect path_noexec() check (see do_mmap()),
+ * but with some future proofing against other cases that may deny
+ * execute permissions.
+ */
+ if (!(vma->vm_flags & VM_MAYEXEC)) {
+ ret = -EACCES;
+ goto out;
+ }
+
+ if (copy_from_user(dst, (void __user *)src, PAGE_SIZE))
+ ret = -EFAULT;
+ else
+ ret = 0;
+
+out:
+ up_read(¤t->mm->mmap_sem);
+
+ return ret;
+}
+
/**
* sgx_ioc_enclave_add_page - handler for %SGX_IOC_ENCLAVE_ADD_PAGE
*
@@ -616,13 +654,12 @@ static long sgx_ioc_enclave_add_page(struct file *filep, unsigned int cmd,
data = kmap(data_page);
- if (copy_from_user((void *)data, (void __user *)addp->src, PAGE_SIZE)) {
- ret = -EFAULT;
- goto out;
- }
-
prot = addp->flags & (PROT_READ | PROT_WRITE | PROT_EXEC);
+ ret = sgx_encl_page_copy(data, addp->src, prot);
+ if (ret)
+ goto out;
+
ret = sgx_encl_add_page(encl, addp->addr, data, &secinfo, addp->mrmask,
prot);
if (ret)
--
2.21.0
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