On Mon, 2022-07-18 at 17:18 -0400, J. Bruce Fields wrote: > On Thu, Jul 14, 2022 at 11:28:16AM -0400, Jeff Layton wrote: > > Here's a first stab at a patchset to close a potential race when setting > > a delegation on a file. Between the point where we open the file and > > where we set the delegation, another task or client could unlink or > > rename the dentry. If that occurs, we shouldn't hand out a delegation > > in the open response, but we don't prevent that today. > > > > The basic idea here is to re-do the lookup after setting the delegation. > > If the resulting dentry is not the one we have in the open, then we can > > reject handing out a delegation. > > I have this distinct memory of actually doing that before. > > But looking through the git history all I find is 4335723e8e9f "nfsd4: > fix delegation-unlink/rename race", from 2014, which claims to fix a > similar-sounding race in a different way. > > How are you reproducing this? > > --b. > I'm not at all, so far. This race is entirely theoretical. Probably we could reproduce it by introducing some artificial delays or something. > > > > Only lightly tested, so this is an RFC for now. > > > > Jeff Layton (3): nfsd: drop fh argument from alloc_init_deleg nfsd: > > rework arguments to nfs4_set_delegation nfsd: vet the opened dentry > > after setting a delegation > > > > fs/nfsd/nfs4state.c | 65 > > ++++++++++++++++++++++++++++++++++++++------- 1 file changed, 55 > > insertions(+), 10 deletions(-) > > > > -- 2.36.1 -- Jeff Layton <jlayton@xxxxxxxxxx>
