On Wed 11-10-23 17:27:37, Christian Brauner wrote: > On Wed, Oct 11, 2023 at 03:59:22PM +0200, Jan Kara wrote: > > On Wed 11-10-23 14:27:49, Max Kellermann wrote: > > > On Wed, Oct 11, 2023 at 2:18 PM Max Kellermann <max.kellermann@xxxxxxxxx> wrote: > > > > But without the other filesystems. I'll resend it with just the > > > > posix_acl.h hunk. > > > > > > Thinking again, I don't think this is the proper solution. This may > > > server as a workaround so those broken filesystems don't suffer from > > > this bug, but it's not proper. > > > > > > posix_acl_create() is only supposed to appy the umask if the inode > > > supports ACLs; if not, the VFS is supposed to do it. But if the > > > filesystem pretends to have ACL support but the kernel does not, it's > > > really a filesystem bug. Hacking the umask code into > > > posix_acl_create() for that inconsistent case doesn't sound right. > > > > > > A better workaround would be this patch: > > > https://patchwork.kernel.org/project/linux-nfs/patch/151603744662.29035.4910161264124875658.stgit@xxxxxxxxxxxxxxxx-ag/ > > > I submitted it more than 5 years ago, it got one positive review, but > > > was never merged. > > > > > > This patch enables the VFS's umask code even if the filesystem > > > prerents to support ACLs. This still doesn't fix the filesystem bug, > > > but makes VFS's behavior consistent. > > > > OK, that solution works for me as well. I agree it seems a tad bit cleaner. > > Christian, which one would you prefer? > > So it always bugged me that POSIX ACLs push umask stripping down into > the individual filesystems but it's hard to get rid of this. And we > tried to improve the situation during the POSIX ACL rework by > introducing vfs_prepare_umask(). > > Aside from that, the problem had been that filesystems like nfs v4 > intentionally raised SB_POSIXACL to prevent umask stripping in the VFS. > IOW, for them SB_POSIXACL was equivalent to "don't apply any umask". Ah, what a hack... > And afaict nfs v4 has it's own thing going on how and where umasks are > applied. However, since we now have the following commit in vfs.misc: > > commit f61b9bb3f8386a5e59b49bf1310f5b34f47bcef9 > Author: Jeff Layton <jlayton@xxxxxxxxxx> > AuthorDate: Mon Sep 11 20:25:50 2023 -0400 > Commit: Christian Brauner <brauner@xxxxxxxxxx> > CommitDate: Thu Sep 21 15:37:47 2023 +0200 > > fs: add a new SB_I_NOUMASK flag > > SB_POSIXACL must be set when a filesystem supports POSIX ACLs, but NFSv4 > also sets this flag to prevent the VFS from applying the umask on > newly-created files. NFSv4 doesn't support POSIX ACLs however, which > causes confusion when other subsystems try to test for them. > > Add a new SB_I_NOUMASK flag that allows filesystems to opt-in to umask > stripping without advertising support for POSIX ACLs. Set the new flag > on NFSv4 instead of SB_POSIXACL. > > Also, move mode_strip_umask to namei.h and convert init_mknod and > init_mkdir to use it. > > Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx> > Message-Id: <20230911-acl-fix-v3-1-b25315333f6c@xxxxxxxxxx> > Signed-off-by: Christian Brauner <brauner@xxxxxxxxxx> > > I think it's possible to pick up the first patch linked above: > > fix umask on NFS with CONFIG_FS_POSIX_ACL=n doesn't lead to any > > and see whether we see any regressions from this. > > The second patch I can't easily judge that should go through nfs if at > all. > > So proposal/question: should we take the first patch into vfs.misc? Sounds good to me. I have checked whether some other filesystem does not try to play similar games as NFS and it appears not although overlayfs does seem to play some games with umasks. Honza -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR
