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SubjectRe: [PATCH] autofs4 - fix comms packet struct size
On Sun, 19 Feb 2006, Christoph Hellwig wrote:

> On Sun, Feb 19, 2006 at 10:11:31PM +0800, Ian Kent wrote:
> >
> > Set userspace communication struct fields to fixed size.
> >
> > Signed-off-by: Ian Kent <raven@themaw.net>
> >
> > --- linux-2.6.16-rc3-mm1/include/linux/auto_fs4.h.fix-v5-packet-size 2006-02-17 19:15:49.000000000 +0800
> > +++ linux-2.6.16-rc3-mm1/include/linux/auto_fs4.h 2006-02-17 19:12:09.000000000 +0800
> > @@ -65,10 +65,10 @@ struct autofs_v5_packet {
> > autofs_wqt_t wait_queue_token;
>
> Hiding types in user visible structures behind typedefs is bad.
> What type is behind this? If this is not an __u32 you have
> a padding issue.

This has been an occassion problem for a long time.
Since it dates back to way before version 4 I have always been reluctant
to change it. I'd rather leave it as is unless you really can't accept it.

>
> > __u32 dev;
> > __u64 ino;
> > - uid_t uid;
> > - gid_t gid;
> > - pid_t pid;
> > - pid_t tgid;
> > + __u64 uid;
> > + __u64 gid;
> > + __u64 pid;
> > + __u64 tgid;
>
> These should be 32bit values.

OK. But will they be 32 bit for the life of this struct?

Once userspace programs are using this it can't ever change.

>
> > int len;
>
> this should become a fixed-size type aswell.

OK. That shouldn't cause a problem. I'll change that also.

>
> > char name[NAME_MAX+1];
> > };
> > --- linux-2.6.16-rc3-mm1/fs/autofs4/autofs_i.h.fix-v5-packet-size 2006-02-17 19:17:03.000000000 +0800
> > +++ linux-2.6.16-rc3-mm1/fs/autofs4/autofs_i.h 2006-02-17 19:17:25.000000000 +0800
> > @@ -79,10 +79,10 @@ struct autofs_wait_queue {
> > char *name;
> > u32 dev;
> > u64 ino;
> > - uid_t uid;
> > - gid_t gid;
> > - pid_t pid;
> > - pid_t tgid;
> > + u64 uid;
> > + u64 gid;
> > + u64 pid;
> > + u64 tgid;
> > /* This is for status reporting upon return */
> > int status;
> > atomic_t notified;
>
> This is an in-kernel structure, isn't it? No need to use u64 here.

Yes, I was thinking the same thing when I did it.
I'll fix that.

Thanks Christoph.

Ian

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