On Thu 21-01-21 14:27:18, Mike Rapoport wrote: > From: Mike Rapoport <rppt@xxxxxxxxxxxxx> > > Introduce "memfd_secret" system call with the ability to create memory > areas visible only in the context of the owning process and not mapped not > only to other processes but in the kernel page tables as well. > > The user will create a file descriptor using the memfd_secret() system > call. The memory areas created by mmap() calls from this file descriptor > will be unmapped from the kernel direct map and they will be only mapped in > the page table of the owning mm. > > The secret memory remains accessible in the process context using uaccess > primitives, but it is not accessible using direct/linear map addresses. > > Functions in the follow_page()/get_user_page() family will refuse to return > a page that belongs to the secret memory area. > > A page that was a part of the secret memory area is cleared when it is > freed. > > The following example demonstrates creation of a secret mapping (error > handling is omitted): > > fd = memfd_secret(0); > ftruncate(fd, MAP_SIZE); > ptr = mmap(NULL, MAP_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0); I do not see any access control or permission model for this feature. Is this feature generally safe to anybody? -- Michal Hocko SUSE Labs
