On Wed, Jul 08, 2020 at 07:10:27PM +0300, Jarkko Sakkinen wrote: > On Wed, Jul 08, 2020 at 03:37:08PM +0100, Matthew Wilcox wrote: > > On Wed, Jul 08, 2020 at 05:33:20PM +0300, Jarkko Sakkinen wrote: > > > I get the point but I don't think that your proposal could work given > > > that mprotect-callback takes neither 'prev' nor 'newflags' as its > > > parameters. The current callback has no means to call mprotect_fixup() > > > properly. > > > > > > It would have to be extended > > > > > > int (*mprotect)(struct vm_area_struct *vma, > > > struct vm_area_struct **pprev, unsigned long start, > > > unsigned long end, unsigned long prot, > > > unsigned long newflags); > > > > > > Is this what you want? > > > > https://lore.kernel.org/linux-mm/20200625173050.GF7703@xxxxxxxxxxxxxxxxxxxx/ > > Ugh, it's there as it should be. I'm sorry - I just misread the code. > > I think that should work, and we do not have to do extra conversion > inside the callback. > > There is still one thing that I'm wondering. 'page->vm_max_prot_bits' > contains some an union of subset of {VM_READ, VM_WRITE, VM_EXEC}, and > 'newflags' can contain other bits set too. > > The old implementation of sgx_vma_mprotect() is like this: > > static int sgx_vma_mprotect(struct vm_area_struct *vma, unsigned long start, > unsigned long end, unsigned long prot) > { > return sgx_encl_may_map(vma->vm_private_data, start, end, > calc_vm_prot_bits(prot, 0)); > } > > The new one should be probably the implemented along the lines of > > static int sgx_vma_mprotect(struct vm_area_struct *vma, > struct vm_area_struct **pprev, unsigned long start, > unsigned long end, unsigned long newflags) > { > unsigned long masked_newflags = newflags & > (VM_READ | VM_WRITE | VM_EXEC); > int ret; > > ret = sgx_encl_may_map(vma->vm_private_data, start, end, > masked_newflags); > if (ret) > return ret; > > return mprotect_fixup(vma, pprev, start, end, newflags); > } > > Alternatively the filtering can be inside sgx_encl_may_map(). Perhaps > that is a better place for it. This was just easier function to > represent the idea. Turned out that mmap() handler was already masking with RWX. So I removed masking from there and do it as the first step in sgx_encl_may_map(), which is called by the both handlers: int sgx_encl_may_map(struct sgx_encl *encl, unsigned long start, unsigned long end, unsigned long vm_flags) { unsigned long vm_prot_bits = vm_flags & (VM_READ | VM_WRITE | VM_EXEC); unsigned long idx, idx_start, idx_end; struct sgx_encl_page *page; Also renamed the last function parameter from vm_flags to vm_port_bits. Kind of makes the flow more understandable (i.e. vm_prot_bits is purely internal representation, not something caller needs to be concerned of). /Jarkko
