On Fri, Aug 23, 2024 at 10:44 AM Chuck Lever <chuck.lever@xxxxxxxxxx> wrote:
>
> On Fri, Aug 23, 2024 at 10:14:01AM -0400, Olga Kornievskaia wrote:
> > states_show() relied on sc_type field to be of valid type
> > before calling into a subfunction to show content of a
> > particular stateid. But from commit 3f29cc82a84c we
> > split the validity of the stateid into sc_status and no longer
> > changed sc_type to 0 while unhashing the stateid. This
> > resulted in kernel oopsing as something like
> > nfs4_show_open() would derefence sc_file which was NULL.
> >
> > To reproduce: mount the server with 4.0, read and close
> > a file and then on the server cat /proc/fs/nfsd/clients/2/states
> >
> > [ 513.590804] Call trace:
> > [ 513.590925] _raw_spin_lock+0xcc/0x160
> > [ 513.591119] nfs4_show_open+0x78/0x2c0 [nfsd]
> > [ 513.591412] states_show+0x44c/0x488 [nfsd]
> > [ 513.591681] seq_read_iter+0x5d8/0x760
> > [ 513.591896] seq_read+0x188/0x208
> > [ 513.592075] vfs_read+0x148/0x470
> > [ 513.592241] ksys_read+0xcc/0x178
> >
> > Fixes: 3f29cc82a84c ("nfsd: split sc_status out of sc_type")
> > Signed-off-by: Olga Kornievskaia <okorniev@xxxxxxxxxx>
> > ---
> > fs/nfsd/nfs4state.c | 3 +++
> > 1 file changed, 3 insertions(+)
> >
> > diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> > index c3def49074a4..8351724b8a43 100644
> > --- a/fs/nfsd/nfs4state.c
> > +++ b/fs/nfsd/nfs4state.c
> > @@ -2907,6 +2907,9 @@ static int states_show(struct seq_file *s, void *v)
> > {
> > struct nfs4_stid *st = v;
> >
> > + if (!st->sc_file)
> > + return 0;
> > +
> > switch (st->sc_type) {
> > case SC_TYPE_OPEN:
> > return nfs4_show_open(s, st);
> > --
> > 2.43.5
> >
>
> I'll wait for Neil/Jeff's Reviewed-by, but the root cause analysis
> seems plausible to me, and I'll plan to apply it for v6.11-rc.
>
> Btw, I noticed this at the tail of states_show():
>
> /* XXX: copy stateids? */
>
> I'm not really sure, but those won't ever have an sc_file, will
> they? Are COPY callback stateids something we want the server to
> display in this code? Just musing aloud: maybe the NULL sc_file
> check wants to be moved into the show helpers.
I can see that the copy stateids still have type NFS4_COPY_STID so
they are not converted to the new type of SC_TYPE. But it just means
we are not displaying them. I'm not sure what happens to sc_file for
copy stateid, I'd need to check.
>
> --
> Chuck Lever
>
