Hi On Thu, Mar 20, 2014 at 4:32 PM, <tytso@xxxxxxx> wrote: > Why not make sealing an attribute of the "struct file", and enforce it > at the VFS layer? That way all file system objects would have access > to sealing interface, and for memfd_shmem, you can't get another > struct file pointing at the object, the security properties would be > identical. Sealing as introduced here is an inode-attribute, not "struct file". This is intentional. For instance, a gfx-client can get a read-only FD via /proc/self/fd/ and pass it to the compositor so it can never overwrite the contents (unless the compositor has write-access to the inode itself, in which case it can just re-open it read-write). Furthermore, I don't see any use-case besides memfd for sealing, so I purposely avoided changing core VFS interfaces. Protecting page-allocation/access for SEAL_WRITE like I do in shmem.c is not that easy to do generically. So if we moved this interface to "struct inode", all that would change is moving "u32 seals;" from one struct to the other. Ok, some protections might get easily implemented generically, but I without proper insight in the underlying implemenation, I couldn't verify all paths and possible races. Isn't keeping the API generic enough so far? Changing the underlying implementation can be done once we know what we want. Thanks David -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>