linux-kernel - RE: [PATCH v2] NFSv4: try lease recovery on NFS4ERR

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Wed, 22 Jan 2020 14:20:09 -0000
From:   "Robert Milkowski" <rmilkowski@...il.com>
To:     "'Trond Myklebust'" <trondmy@...merspace.com>,
        <linux-nfs@...r.kernel.org>
Cc:     <anna.schumaker@...app.com>, <linux-kernel@...r.kernel.org>,
        <chuck.lever@...cle.com>
Subject: RE: [PATCH v2] NFSv4: try lease recovery on NFS4ERR_EXPIRED

> -----Original Message-----
> From: Trond Myklebust <trondmy@...merspace.com>
> Sent: 17 January 2020 17:24
> To: linux-nfs@...r.kernel.org; rmilkowski@...il.com
> Cc: anna.schumaker@...app.com; linux-kernel@...r.kernel.org;
> chuck.lever@...cle.com
> Subject: Re: [PATCH v2] NFSv4: try lease recovery on NFS4ERR_EXPIRED
> 
> On Fri, 2020-01-17 at 16:12 +0000, Robert Milkowski wrote:
> > Anyone please?
> >
> >
> > -----Original Message-----
> > From: Robert Milkowski <rmilkowski@...il.com>
> > Sent: 08 January 2020 21:48
> > To: linux-nfs@...r.kernel.org
> > Cc: 'Trond Myklebust' <trondmy@...merspace.com>; 'Chuck Lever'
> > <chuck.lever@...cle.com>; 'Anna Schumaker' <anna.schumaker@...app.com
> > >;
> > linux-kernel@...r.kernel.org
> > Subject: [PATCH v2] NFSv4: try lease recovery on NFS4ERR_EXPIRED
> >
> > From: Robert Milkowski <rmilkowski@...il.com>
> >
> > Currently, if an nfs server returns NFS4ERR_EXPIRED to open(), etc.
> > we return EIO to applications without even trying to recover.
> >
> > Fixes: 272289a3df72 ("NFSv4: nfs4_do_handle_exception() handle
> > revoke/expiry of a single stateid")
> > Signed-off-by: Robert Milkowski <rmilkowski@...il.com>
> > ---
> >  fs/nfs/nfs4proc.c | 4 ++++
> >  1 file changed, 4 insertions(+)
> >
> > diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c index
> > 76d3716..2478405
> > 100644
> > --- a/fs/nfs/nfs4proc.c
> > +++ b/fs/nfs/nfs4proc.c
> > @@ -481,6 +481,10 @@ static int nfs4_do_handle_exception(struct
> > nfs_server *server,
> >  						stateid);
> >  				goto wait_on_recovery;
> >  			}
> > +			if (state == NULL) {
> > +				nfs4_schedule_lease_recovery(clp);
> > +				goto wait_on_recovery;
> > +			}
> >  			/* Fall through */
> >  		case -NFS4ERR_OPENMODE:
> >  			if (inode) {
> > --
> > 1.8.3.1
> >
> >
> 
> Does this apply to any case other than NFS4ERR_EXPIRED in the specific
> case of nfs4_do_open()? I can't see that it does. It looks to me as if
> the open recovery routines already have their own handling of this case.

I only observed the issue with open(). After further
review I think you are right and it only applies to nfs4_do_open().


> 
> If so, why not just add it as a special case in the nfs4_do_open() error
> handling? Otherwise this patch will end up overriding other generic
> cases where we have an inode, but no open state.
> 

Fair point.
So perhaps, few lines further instead of:

			if (inode) {
...
			if (state == NULL) {
					break;
			}

There should be:

			if (inode) {
...
			if (state == NULL) {
				nfs4_schedule_lease_recovery(clp);
				goto wait_on_recovery;
			}



This way we know that inode cannot be null at this point, and it's a case where both inode and state are NULL.
This would be a little bit more general in case we reach this point.

But if you think it is better to move it to nfs4_do_open() then I've just tested the following patch:

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 76d3716..b7c4044 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -3187,6 +3187,11 @@ static struct nfs4_state *nfs4_do_open(struct inode *dir,
                        exception.retry = 1;
                        continue;
                }
+               if (status == -NFS4ERR_EXPIRED) {
+                       nfs4_schedule_lease_recovery(server->nfs_client);
+                       exception.retry = 1;
+                       continue;
+               }
                if (status == -EAGAIN) {
                        /* We must have found a delegation */
                        exception.retry = 1;



Please let me know which way you want to proceed and I will submit an updated patch.



> Note that _nfs4_do_open() already waits for lease recovery, so we only
> need the call to nfs_schedule_lease_recovery().
>

Yep

-- 
Robert Milkowski