On Thu, Feb 6, 2025 at 9:24 PM Jeff Layton <jlayton@xxxxxxxxxx> wrote:
>
> On Thu, 2025-02-06 at 20:07 +0100, Mateusz Guzik wrote:
> > You added it in:
> > commit 7ac86265dc8f665cc49d6e60a125e608cd2fca14
> > Author: Jeff Layton <jlayton@xxxxxxxxxx>
> > Date: Wed Oct 10 15:25:28 2012 -0400
> >
> > audit: allow audit code to satisfy getname requests from its names_list
> >
> > Do I read correctly this has no user-visible impact, but merely tries
> > to shave off some memory usage in case of duplicated user bufs?
> >
> > This is partially getting in the way of whacking atomics for filename
> > ref management (but can be worked around).
> >
> > AFAIU this change is not all *that* beneficial in its own right, so
> > should not be a big deal to whack it regardless of what happens with
> > refs? Note it would also remove some branches in the common case as
> > normally audit either has dummy context or there is no match anyway.
>
>
> (cc'ing audit folks and mailing list)
>
> IIRC, having duplicate audit_names records can cause audit to emit
> extra name records in this loop in audit_log_exit():
>
> list_for_each_entry(n, &context->names_list, list) {
> if (n->hidden)
> continue;
> audit_log_name(context, n, NULL, i++, &call_panic);
> }
>
>
> ...which is something you probably want to avoid.
Well in this case I would argue the current code is buggy, unless I'm
misunderstanding something.
audit_log_name in particular logs:
1550 │ if (n->ino != AUDIT_INO_UNSET)
1551 │ audit_log_format(ab, " inode=%lu dev=%02x:%02x
mode=%#ho ouid=%u ogid=%u rdev=%02x
1552 │ n->ino,
1553 │ MAJOR(n->dev),
1554 │ MINOR(n->dev),
1555 │ n->mode,
1556 │ from_kuid(&init_user_ns, n->uid),
1557 │ from_kgid(&init_user_ns, n->gid),
1558 │ MAJOR(n->rdev),
1559 │ MINOR(n->rdev));
As in it grabs the properties of the found inode.
Suppose the 2 lookups of the same path name found 2 different inodes
as someone was mucking with the filesystem at the same time.
Then this is going to *fail* to record the next inode.
So if any dedup is necessary, it should be done by audit when logging imo.
--
Mateusz Guzik <mjguzik gmail.com>
