On Thu, Feb 11, 2021 at 01:07:10PM +0100, David Hildenbrand wrote: > On 11.02.21 12:27, Mike Rapoport wrote: > > On Thu, Feb 11, 2021 at 10:01:32AM +0100, David Hildenbrand wrote: > > So let's talk about the main user-visible differences to other memfd files > (especially, other purely virtual files like hugetlbfs). With secretmem: > > - File content can only be read/written via memory mappings. > - File content cannot be swapped out. > > I think there are still valid ways to modify file content using syscalls: > e.g., fallocate(PUNCH_HOLE). Things like truncate also seems to work just > fine. These work perfectly with any file, so maybe we should have added memfd_create as a flag to open(2) back then and now the secretmem file descriptors? > > > AFAIKS, we would need MFD_SECRET and disallow > > > MFD_ALLOW_SEALING and MFD_HUGETLB. > > > > So here we start to multiplex. > > Yes. And as Michal said, maybe we can support combinations in the future. Isn't there a general agreement that syscall multiplexing is not a good thing? memfd_create already has flags validation that does not look very nice. Adding there only MFD_SECRET will make it a bit less nice, but when we'll grow new functionality into secretmem that will become horrible. -- Sincerely yours, Mike.
