On Mon, Sep 23, 2024 at 4:37 PM Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote: > On Mon, Sep 23, 2024 at 12:14:29PM -0400, Paul Moore wrote: > > [ordering and number of PATH items for syscall] > > > >From my point of view, stuff like that is largely driven by enterprise > > distros chasing 3rd party security certifications so they can sell > > products/services to a certain class of users. These are the same > > enterprise distros that haven't really bothered to contribute a lot to > > the upstream Linux kernel's audit subsystem lately so I'm not going to > > worry too much about them at this point. > > Umm... IIRC, sgrubb had been involved in the spec-related horrors, but > that was a long time ago... Yep, he was. Last I spoke to Steve a year or so ago, audit was no longer part of his job description; Steve still maintains his userspace audit tools, but that is a nights/weekends job as far as I understand. The last time I was involved in any audit/CC spec related work was well over a decade ago now, and all of those CC protection profiles have long since expired and been replaced. > > where I would like to take audit ... eventually). Assuming your ideas > > for struct filename don't significantly break audit you can consider > > me supportive so long as we still have a way to take a struct filename > > reference inside the audit_context; we need to keep that ref until > > syscall/io_uring-op exit time as we can't be certain if we need to log > > the PATH until we know the success/fail status of the operation (among > > other things). > > OK... As for what I would like to do: > > * go through the VFS side of things and make sure we have a consistent > set of helpers that would take struct filename * - *not* the ad-hoc mix we > have right now, when that's basically driven by io_uring borging them in > one by one - or duplicates them without bothering to share helpers. > E.g. mkdirat(2) does getname() and passes it to do_mkdirat(), which > consumes the sucker; so does mknodat(2), but do_mknodat() is static. OTOH, > path_setxattr() does setxattr_copy(), then retry_estale loop with > user_path_at() + mnt_want_write() + do_setxattr() + mnt_drop_write() + path_put() > as a body, while on io_uring side we have retry_estale loop with filename_lookup() + > (io_uring helper that does mnt_want_write() + do_setxattr() + mnt_drop_write()) + > path_put(). > Sure, that user_path_at() call is getname() + filename_lookup() + putname(), > so they are equivalent, but keeping that shite in sync is going to be trouble. I obviously trust you to do the right thing with the VFS bits, and having a well defined struct filename interface sounds like a good thing from an audit perspective. I don't believe it completely solves the audit/io_uring issue, but it should make things easier and hopefully will result in less chance of breakage in the future. > * get rid of the "repeated getname() on the same address is going to > give you the same object" - that can't be relied upon without audit, for one > thing and for another... having a syscall that takes two pathnames that gives > different audit log (if not predicate evaluation) in cases when those are > identical pointers vs. strings with identical contenst is, IMO, somewhat > undesirable. That kills filename->uaddr. /uaddr/uptr/ if I'm following you correctly, but yeah, that all seems good. > * looking at the users of that stuff, I would probably prefer to > separate getname*() from insertion into audit context. It's not that > tricky - __set_nameidata() catches *everything* that uses nd->name (i.e. > all that audit_inode() calls in fs/namei.c use). That should be a pretty significant simplification, that sounds good to me. > ... What remains is > do_symlinkat() for symlink body > fs_index() on the argument (if we want to bother - it's a part > of weird Missed'em'V sysfs(2) syscall; I sincerely doubt that there's > anybody who'd use it) We probably should bother, folks that really care about audit don't like blind spots. Perhaps make it a separate patch if it isn't too ugly to split it out. > fsconfig(2) FSCONFIG_SET_PATH handling. > mq_open(2) and mq_unlink(2) - those bypass the normal pathwalk > logics, so __set_nameidata() won't catch them. > _maybe_ alpha osf_mount(2) devname argument; or we could get rid > of that stupidity and have it use copy_mount_string() like mount(2) does, > instead of messing with getname(). > That's all it takes. With that done, we can kill ->aname; > just look in the ->names_list for the first entry with given ->name - > as in, given struct filename * value, no need to look inside. Seems reasonable to me. I can't imagine these special cases being any worse than what we have now in fs/namei.c, and if nothing else having a single catch point for the bulk of the VFS lookups makes it worth it as far as I'm concerned. -- paul-moore.com
