Re: [PATCH 1/8] mm/fs: don't allow writes to immutable files

Darrick J. Wong
2019-06-10T16:09:45Z

On Mon, Jun 10, 2019 at 09:14:17AM -0400, Theodore Ts'o wrote:
> On Sun, Jun 09, 2019 at 09:41:44PM -0700, Darrick J. Wong wrote:
> > On Sun, Jun 09, 2019 at 09:51:45PM -0400, Theodore Ts'o wrote:
> > > On Wed, Apr 17, 2019 at 12:04:33PM -0700, Darrick J. Wong wrote:
> >
> > > Shouldn't this check be moved before the modification of vmf->flags?
> > > It looks like do_page_mkwrite() isn't supposed to be returning with
> > > vmf->flags modified, lest "the caller gets surprised".
> >
> > Yeah, I think that was a merge error during a rebase... :(
> >
> > Er ... if you're still planning to take this patch through your tree,
> > can you move it to above the "vmf->flags = FAULT_FLAG_WRITE..." ?
>
> I was planning on only taking 8/8 through the ext4 tree. I also added
> a patch which filtered writes, truncates, and page_mkwrites (but not
> mmap) for immutable files at the ext4 level.

*Oh*. I saw your reply attached to the 1/8 patch and thought that was
the one you were taking. I was sort of surprised, tbh. :)

> I *could* take this patch through the mm/fs tree, but I wasn't sure
> what your plans were for the rest of the patch series, and it seemed
> like it hadn't gotten much review/attention from other fs or mm folks
> (well, I guess Brian Foster weighed in).

> What do you think?

Not sure. The comments attached to the LWN story were sort of nasty,
and now that a couple of people said "Oh, well, Debian documented the
inconsistent behavior so just let it be" I haven't felt like
resurrecting the series for 5.3.

I do want to clean up the parameter validation for the VFS SETFLAGS and
FSSETXATTR ioctls though... eh, maybe I'll just send out the series as
it stands now. I'm still maintaining it, so all that work might as well
go somewhere.

--D

>
> - Ted
>
>
>