Re: [PATCH] cifs: Return correct error code from smb2_get_enc_key

From: Pavel Shilovsky <piastryyy@gmail.com>
To: Steve French <smfrench@gmail.com>
Cc: Paul Aurich <paul@darkrain42.org>, CIFS <linux-cifs@vger.kernel.org>
Subject: Re: [PATCH] cifs: Return correct error code from smb2_get_enc_key
Date: Wed, 14 Apr 2021 15:24:07 -0700	[thread overview]
Message-ID: <CAKywueT+SGRaE7Ttq0BAum2QaXtO1D13FtYej_rLZ9JSuz5t9g@mail.gmail.com> (raw)
In-Reply-To: <CAH2r5mtg3Yw7=3E_JExhaG=x3qZLsXJvG8L+ynkwprfLrYiPLA@mail.gmail.com>

If we can't find an encryption key that means that there was a
reconnect and an SMB session associated with the packet is gone. If
this happens during the writeback (as in the trace above) I would
rather retry instead of returning an error.

I think we should use -EAGAIN instead, so the upper layer will attempt
to retry the write request if such an error occurs.

--
Best regards,
Pavel Shilovsky

ср, 14 апр. 2021 г. в 12:49, Steve French <smfrench@gmail.com>:
>
> tentatively merged into cifs-2.6.git for-next pending more reviews
> from Pavel etc and testing
>
> On Wed, Apr 14, 2021 at 1:56 AM Paul Aurich <paul@darkrain42.org> wrote:
> >
> > Avoid a warning if the error percolates back up:
> >
> > [440700.376476] CIFS VFS: \\otters.example.com crypt_message: Could not get encryption key
> > [440700.386947] ------------[ cut here ]------------
> > [440700.386948] err = 1
> > [440700.386977] WARNING: CPU: 11 PID: 2733 at /build/linux-hwe-5.4-p6lk6L/linux-hwe-5.4-5.4.0/lib/errseq.c:74 errseq_set+0x5c/0x70
> > ...
> > [440700.397304] CPU: 11 PID: 2733 Comm: tar Tainted: G           OE     5.4.0-70-generic #78~18.04.1-Ubuntu
> > ...
> > [440700.397334] Call Trace:
> > [440700.397346]  __filemap_set_wb_err+0x1a/0x70
> > [440700.397419]  cifs_writepages+0x9c7/0xb30 [cifs]
> > [440700.397426]  do_writepages+0x4b/0xe0
> > [440700.397444]  __filemap_fdatawrite_range+0xcb/0x100
> > [440700.397455]  filemap_write_and_wait+0x42/0xa0
> > [440700.397486]  cifs_setattr+0x68b/0xf30 [cifs]
> > [440700.397493]  notify_change+0x358/0x4a0
> > [440700.397500]  utimes_common+0xe9/0x1c0
> > [440700.397510]  do_utimes+0xc5/0x150
> > [440700.397520]  __x64_sys_utimensat+0x88/0xd0
> >
> > Fixes: 61cfac6f267d ("CIFS: Fix possible use after free in demultiplex thread")
> > Signed-off-by: Paul Aurich <paul@darkrain42.org>
> > CC: stable@vger.kernel.org
> > ---
> >  fs/cifs/smb2ops.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
> > index 61214b23c57f..caa5432a5ed1 100644
> > --- a/fs/cifs/smb2ops.c
> > +++ b/fs/cifs/smb2ops.c
> > @@ -4418,7 +4418,7 @@ smb2_get_enc_key(struct TCP_Server_Info *server, __u64 ses_id, int enc, u8 *key)
> >         }
> >         spin_unlock(&cifs_tcp_ses_lock);
> >
> > -       return 1;
> > +       return -ENOENT;
> >  }
> >  /*
> >   * Encrypt or decrypt @rqst message. @rqst[0] has the following format:
> > --
> > 2.31.0
> >
>
>
> --
> Thanks,
>
> Steve