| Message ID | 20190619222401.14942-6-sean.j.christopherson@intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | security: x86/sgx: SGX vs. LSM | expand |
On Wed, Jun 19, 2019 at 03:23:54PM -0700, Sean Christopherson wrote: > 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. > > Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> > --- > arch/x86/kernel/cpu/sgx/driver/ioctl.c | 42 +++++++++++++++++++++++--- > 1 file changed, 37 insertions(+), 5 deletions(-) > > diff --git a/arch/x86/kernel/cpu/sgx/driver/ioctl.c b/arch/x86/kernel/cpu/sgx/driver/ioctl.c > index e18d2afd2aad..1fca70a36ce3 100644 > --- a/arch/x86/kernel/cpu/sgx/driver/ioctl.c > +++ b/arch/x86/kernel/cpu/sgx/driver/ioctl.c > @@ -564,6 +564,39 @@ 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) I will probably forget the context with this name after this has been merged :-) So many functions dealing with enclave pages. Two alternatives that come up to my mind: 1. sgx_encl_page_user_import() 2. sgx_encl_page_user_copy_from() Not saying that they are beatiful names but at least you immediately know the context. > +{ > + struct vm_area_struct *vma; > + int ret; > + > + /* Hold mmap_sem across copy_from_user() to avoid a TOCTOU race. */ > + down_read(¤t->mm->mmap_sem); > + > + /* Query vma's VM_MAYEXEC as an indirect path_noexec() check. */ > + if (prot & PROT_EXEC) { > + vma = find_vma(current->mm, src); > + if (!vma) { > + ret = -EFAULT; > + goto out; Should this be -EINVAL instead? /Jarkko
On Fri, Jun 21, 2019 at 04:26:54AM +0300, Jarkko Sakkinen wrote: > On Wed, Jun 19, 2019 at 03:23:54PM -0700, Sean Christopherson wrote: > > 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. > > > > Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> > > --- > > arch/x86/kernel/cpu/sgx/driver/ioctl.c | 42 +++++++++++++++++++++++--- > > 1 file changed, 37 insertions(+), 5 deletions(-) > > > > diff --git a/arch/x86/kernel/cpu/sgx/driver/ioctl.c b/arch/x86/kernel/cpu/sgx/driver/ioctl.c > > index e18d2afd2aad..1fca70a36ce3 100644 > > --- a/arch/x86/kernel/cpu/sgx/driver/ioctl.c > > +++ b/arch/x86/kernel/cpu/sgx/driver/ioctl.c > > @@ -564,6 +564,39 @@ 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) > > I will probably forget the context with this name after this has been > merged :-) So many functions dealing with enclave pages. Two > alternatives that come up to my mind: > > 1. sgx_encl_page_user_import() > 2. sgx_encl_page_user_copy_from() What about sgx_encl_page_copy_from_user() to align with copy_from_user()? > Not saying that they are beatiful names but at least you immediately > know the context. > > > +{ > > + struct vm_area_struct *vma; > > + int ret; > > + > > + /* Hold mmap_sem across copy_from_user() to avoid a TOCTOU race. */ > > + down_read(¤t->mm->mmap_sem); > > + > > + /* Query vma's VM_MAYEXEC as an indirect path_noexec() check. */ > > + if (prot & PROT_EXEC) { > > + vma = find_vma(current->mm, src); > > + if (!vma) { > > + ret = -EFAULT; > > + goto out; > > Should this be -EINVAL instead? copy_from_user() failure is handled via -EFAULT, this is effectively an equivalent check.
diff --git a/arch/x86/kernel/cpu/sgx/driver/ioctl.c b/arch/x86/kernel/cpu/sgx/driver/ioctl.c index e18d2afd2aad..1fca70a36ce3 100644 --- a/arch/x86/kernel/cpu/sgx/driver/ioctl.c +++ b/arch/x86/kernel/cpu/sgx/driver/ioctl.c @@ -564,6 +564,39 @@ 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; + + /* Hold mmap_sem across copy_from_user() to avoid a TOCTOU race. */ + down_read(¤t->mm->mmap_sem); + + /* Query vma's VM_MAYEXEC as an indirect path_noexec() check. */ + if (prot & PROT_EXEC) { + vma = find_vma(current->mm, src); + if (!vma) { + ret = -EFAULT; + goto out; + } + + 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 * @@ -604,13 +637,12 @@ static long sgx_ioc_enclave_add_page(struct file *filep, void __user *arg) data = kmap(data_page); - if (copy_from_user((void *)data, (void __user *)addp.src, PAGE_SIZE)) { - ret = -EFAULT; - goto out; - } - prot = addp.prot & (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)
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. Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> --- arch/x86/kernel/cpu/sgx/driver/ioctl.c | 42 +++++++++++++++++++++++--- 1 file changed, 37 insertions(+), 5 deletions(-)