On Thu, Dec 5, 2024 at 7:15 PM Rick Macklem <rick.mack...@gmail.com> wrote:
>
> On Thu, Dec 5, 2024 at 6:40 PM Jessica Clarke <jrt...@freebsd.org> wrote:
> >
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> >
> > On 6 Dec 2024, at 02:06, Rick Macklem <rmack...@freebsd.org> wrote:
> > >
> > > The branch main has been updated by rmacklem:
> > >
> > > URL: 
> > > https://cgit.FreeBSD.org/src/commit/?id=bfc8e3308bee23d0f7836d57f32ed8d47da02627
> > >
> > > commit bfc8e3308bee23d0f7836d57f32ed8d47da02627
> > > Author:     Rick Macklem <rmack...@freebsd.org>
> > > AuthorDate: 2024-12-06 02:05:06 +0000
> > > Commit:     Rick Macklem <rmack...@freebsd.org>
> > > CommitDate: 2024-12-06 02:05:06 +0000
> > >
> > >    ext2fs: Fix the size of struct ufid and add a static assert
> > >
> > >    File system specific *fid structures are copied into the generic
> > >    struct fid defined in sys/mount.h.
> > >    As such, they cannot be larger than struct fid.
> > >
> > >    This patch packed the structure and checks via a __Static_assert().
> > >
> > >    Reviewed by:    markj
> > >    MFC after:      2 weeks
> > > ---
> > > sys/fs/ext2fs/ext2_vnops.c | 2 ++
> > > sys/fs/ext2fs/inode.h      | 2 +-
> > > 2 files changed, 3 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/sys/fs/ext2fs/ext2_vnops.c b/sys/fs/ext2fs/ext2_vnops.c
> > > index dfbb11f75421..064c10bd18b2 100644
> > > --- a/sys/fs/ext2fs/ext2_vnops.c
> > > +++ b/sys/fs/ext2fs/ext2_vnops.c
> > > @@ -1889,6 +1889,8 @@ ext2_vptofh(struct vop_vptofh_args *ap)
> > > {
> > > struct inode *ip;
> > > struct ufid *ufhp;
> > > + _Static_assert(sizeof(struct ufid) <= sizeof(struct fid),
> > > +    "struct ufid cannot be larger than struct fid");
> > >
> > > ip = VTOI(ap->a_vp);
> > > ufhp = (struct ufid *)ap->a_fhp;
> > > diff --git a/sys/fs/ext2fs/inode.h b/sys/fs/ext2fs/inode.h
> > > index 9ee1b5672da6..63102deb10b0 100644
> > > --- a/sys/fs/ext2fs/inode.h
> > > +++ b/sys/fs/ext2fs/inode.h
> > > @@ -191,7 +191,7 @@ struct ufid {
> > > uint16_t ufid_pad; /* Force 32-bit alignment. */
> > > ino_t ufid_ino; /* File number (ino). */
> > > uint32_t ufid_gen; /* Generation number. */
> > > -};
> > > +} __packed;
> >
> > Why not just swap ufid_ino and ufid_gen? This will give worse codegen
> > on architectures that don’t assume fast unaligned access.
> You can commit such a change if you'd like, as far as I am concerned.
>
> I suspect few (if any) export ext2fs file systems anyhow, so this structure
> is unlikely to ever be used.
>
> There was a discussion on phabricator in D47879 about reordering
> entries and the consensus there seemed to be avoid doing that,
> although admittedly I think they were referring to the first two fields,
> which match the ones in the generic "struct fid".
>
> rick
ps: I used __packed since that was what markj@ used for cd9660,
      to keep things consistent.

>
> >
> > Jess
> >

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