On Mon, 27 Jul 2015, Stephen Smalley wrote: > On 07/27/2015 03:32 PM, Hugh Dickins wrote: > > On Fri, 24 Jul 2015, Stephen Smalley wrote: > >> --- a/fs/hugetlbfs/inode.c > >> +++ b/fs/hugetlbfs/inode.c > >> @@ -1010,6 +1010,8 @@ struct file *hugetlb_file_setup(const char *name, size_t size, > >> inode = hugetlbfs_get_inode(sb, NULL, S_IFREG | S_IRWXUGO, 0); > >> if (!inode) > >> goto out_dentry; > >> + if (creat_flags == HUGETLB_SHMFS_INODE) > >> + inode->i_flags |= S_PRIVATE; > > > > I wonder if you would do better just to set S_PRIVATE unconditionally > > there. > > > > hugetlb_file_setup() has two callsites, neither of which exposes an fd. > > One of them is shm.c's newseg(), which is getting us into the lockdep > > trouble that you're fixing here. > > > > The other is mmap.c's mmap_pgoff(). Now I don't think that will ever > > get into lockdep trouble (no mutex or rwsem has been taken at that > > point), but might your change above introduce (perhaps now or perhaps > > in future) an inconsistency between how SElinux checks are applied to > > a SHM area, and how they are applied to a MAP_ANONYMOUS|MAP_HUGETLB > > area, and how they are applied to a straight MAP_ANONYMOUS area? > > > > I think your patch as it stands brings SHM into line with > > MAP_ANONYMOUS, but leaves MAP_ANONYMOUS|MAP_HUGETLB going the old way. > > Perhaps an anomaly would appear when mprotect() is used? > > > > It's up to you: I think your patch is okay as is, > > but I just wonder if it has a surprise in store for the future. > > That sounds reasonable, although there is the concern that > hugetlb_file_setup() might be used in the future for files that are > exposed as fds, unless we rename it to hugetlb_kernel_file_setup() or Good idea. > similar to match shmem_kernel_file_setup(). Also should probably be > done as a separate change on top since it isn't directly related to > ipc/shm or fixing this lockdep. Fair enough. -- 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>