On Wed, Nov 08, 2017 at 06:40:22PM -0800, Linus Torvalds wrote: > Anyway, that cmovne noise makes it a bit hard to see the actual part > that matters (and that traps) but I'm almost certain that it's the > "mnt->mnt_sb->s_flags" loading that is part of calculate_f_flags() > when it then does > > flags_by_sb(mnt->mnt_sb->s_flags); > > and I think mnt->mnt_sb is NULL. We know it's not 'mnt' itself that is > NULL, because we wouldn't have gotten this far if it was. > > Now, afaik, mnt->mnt_sb should never be NULL in the first place for a > proper path. And the vfs_statfs() code itself hasn't changed in a > while. > > Which does seem to implicate nfsd as having passed in a bad path to > vfs_statfs(). But I'm not seeing any changes in nfsd either. > > In particular, there are *no* nfsd changes in that 4.13.8..4.13.11 > range. There is a bunch of xfs changes, though. What's the underlying > filesystem that you are exporting? > > But bringing in Al Viro and Bruce Fields explicitly in case they see > something. And Darrick, just in case it might be xfs.
Looking at https://lkml.org/lkml/2017/11/8/1086 for the actual oops... It doesn't remind me of any known issue. And I don't see how we can call vfs_statfs() with a bad path: nfsd4_encode_getattr would have to have been called with nfserr 0 and ga_fhp->fh_export bad. Looking at nfsd4_proc_compound, I can't see how we could get there in the op->status == 0 case without the fh_verify() in nfsd4_getattr having succeeded and assigned the result to ga_fhp. So either I'm overlooking something or the bug's elsewhere. It sounds like you're varying *only* the server version, so there's not much chance that this could be triggered by changes in client behavior? --b.
