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From:   Xingyuan Mo <hdthky0@gmail.com>
Date:   Mon, 12 Dec 2022 19:22:38 +0800
Message-ID: <CALV6CNOO-Ppv7QfqHo9RKivv-1NUrezbuYN2krrNu4REuchtMA@mail.gmail.com>
Subject: Re: [PATCH 1/1] NFSD: fix use-after-free in __nfs42_ssc_open()
To:     Dai Ngo <dai.ngo@oracle.com>
Cc:     chuck.lever@oracle.com, jlayton@kernel.org, kolga@netapp.com,
        linux-nfs@vger.kernel.org, security@kernel.org
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Can I share the patch with the linux-distros list, so that
distros can do their own testing and preparations?

Regards,
Xingyuan Mo

On Mon, Dec 12, 2022 at 3:22 AM Dai Ngo <dai.ngo@oracle.com> wrote:
>
> Problem caused by source's vfsmount being unmounted but remains
> on the delayed unmount list. This happens when nfs42_ssc_open()
> return errors.
> Fixed by removing nfsd4_interssc_connect(), leave the vfsmount
> for the laundromat to unmount when idle time expires.
>
> Reported-by: Xingyuan Mo <hdthky0@gmail.com>
> Signed-off-by: Dai Ngo <dai.ngo@oracle.com>
> ---
>  fs/nfsd/nfs4proc.c | 23 +++++++----------------
>  1 file changed, 7 insertions(+), 16 deletions(-)
>
> diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
> index 8beb2bc4c328..756e42cf0d01 100644
> --- a/fs/nfsd/nfs4proc.c
> +++ b/fs/nfsd/nfs4proc.c
> @@ -1463,13 +1463,6 @@ nfsd4_interssc_connect(struct nl4_server *nss, struct svc_rqst *rqstp,
>         return status;
>  }
>
> -static void
> -nfsd4_interssc_disconnect(struct vfsmount *ss_mnt)
> -{
> -       nfs_do_sb_deactive(ss_mnt->mnt_sb);
> -       mntput(ss_mnt);
> -}
> -
>  /*
>   * Verify COPY destination stateid.
>   *
> @@ -1572,11 +1565,6 @@ nfsd4_cleanup_inter_ssc(struct vfsmount *ss_mnt, struct file *filp,
>  {
>  }
>
> -static void
> -nfsd4_interssc_disconnect(struct vfsmount *ss_mnt)
> -{
> -}
> -
>  static struct file *nfs42_ssc_open(struct vfsmount *ss_mnt,
>                                    struct nfs_fh *src_fh,
>                                    nfs4_stateid *stateid)
> @@ -1762,7 +1750,8 @@ static int nfsd4_do_async_copy(void *data)
>                 struct file *filp;
>
>                 filp = nfs42_ssc_open(copy->ss_mnt, &copy->c_fh,
> -                                     &copy->stateid);
> +                                       &copy->stateid);
> +
>                 if (IS_ERR(filp)) {
>                         switch (PTR_ERR(filp)) {
>                         case -EBADF:
> @@ -1771,7 +1760,7 @@ static int nfsd4_do_async_copy(void *data)
>                         default:
>                                 nfserr = nfserr_offload_denied;
>                         }
> -                       nfsd4_interssc_disconnect(copy->ss_mnt);
> +                       /* ss_mnt will be unmounted by the laundromat */
>                         goto do_callback;
>                 }
>                 nfserr = nfsd4_do_copy(copy, filp, copy->nf_dst->nf_file,
> @@ -1852,8 +1841,10 @@ nfsd4_copy(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
>         if (async_copy)
>                 cleanup_async_copy(async_copy);
>         status = nfserrno(-ENOMEM);
> -       if (nfsd4_ssc_is_inter(copy))
> -               nfsd4_interssc_disconnect(copy->ss_mnt);
> +       /*
> +        * source's vfsmount of inter-copy will be unmounted
> +        * by the laundromat
> +        */
>         goto out;
>  }
>
> --
> 2.9.5
>