On Thu, Nov 5, 2020 at 5:37 PM Ondrej Mosnacek <omosnace@xxxxxxxxxx> wrote:
>
> On Thu, Nov 5, 2020 at 11:12 PM Olga Kornievskaia
> <olga.kornievskaia@xxxxxxxxx> wrote:
> > From: Olga Kornievskaia <kolga@xxxxxxxxxx>
> >
> > Currently, the client will always ask for security_labels if the server
> > returns that it supports that feature regardless of any LSM modules
> > (such as Selinux) enforcing security policy. This adds performance
> > penalty to the READDIR operation.
> >
> > Client adjusts the superblock's support of the security_label based on
> > the server's support but also on the current client's configuration of
> > the LSM module(s). Thus, prior to using the default bitmask in READDIR,
> > this patch checks the server's capabilities and then instructs
> > READDIR to remove FATTR4_WORD2_SECURITY_LABEL from the bitmask.
> >
> > v2: dropping selinux hook and using the sb cap.
>
> Thanks! I'm happy that we managed to avoid adding yet another LSM hook
> in the end :)
>
> >
> > Suggested-by: Ondrej Mosnacek <omosnace@xxxxxxxxxx
> > Suggested-by: Scott Mayhew <smayhew@xxxxxxxxxx>
> > Signed-off-by: Olga Kornievskaia <kolga@xxxxxxxxxx>
> > ---
> > fs/nfs/nfs4proc.c | 3 +++
> > fs/nfs/nfs4xdr.c | 3 ++-
> > include/linux/nfs_xdr.h | 1 +
> > 3 files changed, 6 insertions(+), 1 deletion(-)
> >
> > diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
> > index 9e0ca9b2b210..9c9d9aa2a8f8 100644
> > --- a/fs/nfs/nfs4proc.c
> > +++ b/fs/nfs/nfs4proc.c
> > @@ -4968,6 +4968,7 @@ static int _nfs4_proc_readdir(struct dentry *dentry, const struct cred *cred,
> > .count = count,
> > .bitmask = NFS_SERVER(d_inode(dentry))->attr_bitmask,
> > .plus = plus,
> > + .labels = true,
> > };
> > struct nfs4_readdir_res res;
> > struct rpc_message msg = {
> > @@ -4981,6 +4982,8 @@ static int _nfs4_proc_readdir(struct dentry *dentry, const struct cred *cred,
> > dprintk("%s: dentry = %pd2, cookie = %Lu\n", __func__,
> > dentry,
> > (unsigned long long)cookie);
> > + if (!(NFS_SB(dentry->d_sb)->caps & NFS_CAP_SECURITY_LABEL))
> > + args.labels = false;
>
> Minor nit: you could initialize .labels directly in the initializer of
> "args" like this:
>
> .labels = !!(NFS_SB(dentry->d_sb)->caps & NFS_CAP_SECURITY_LABEL),
Thank you. v3 will have it.
>
> > nfs4_setup_readdir(cookie, NFS_I(dir)->cookieverf, dentry, &args);
> > res.pgbase = args.pgbase;
> > status = nfs4_call_sync(NFS_SERVER(dir)->client, NFS_SERVER(dir), &msg, &args.seq_args, &res.seq_res, 0);
> > diff --git a/fs/nfs/nfs4xdr.c b/fs/nfs/nfs4xdr.c
> > index c6dbfcae7517..585d5b5cc3dc 100644
> > --- a/fs/nfs/nfs4xdr.c
> > +++ b/fs/nfs/nfs4xdr.c
> > @@ -1605,7 +1605,8 @@ static void encode_readdir(struct xdr_stream *xdr, const struct nfs4_readdir_arg
> > FATTR4_WORD1_OWNER_GROUP|FATTR4_WORD1_RAWDEV|
> > FATTR4_WORD1_SPACE_USED|FATTR4_WORD1_TIME_ACCESS|
> > FATTR4_WORD1_TIME_METADATA|FATTR4_WORD1_TIME_MODIFY;
> > - attrs[2] |= FATTR4_WORD2_SECURITY_LABEL;
> > + if (readdir->labels)
> > + attrs[2] |= FATTR4_WORD2_SECURITY_LABEL;
> > dircount >>= 1;
> > }
> > /* Use mounted_on_fileid only if the server supports it */
> > diff --git a/include/linux/nfs_xdr.h b/include/linux/nfs_xdr.h
> > index d63cb862d58e..95f648b26525 100644
> > --- a/include/linux/nfs_xdr.h
> > +++ b/include/linux/nfs_xdr.h
> > @@ -1119,6 +1119,7 @@ struct nfs4_readdir_arg {
> > unsigned int pgbase; /* zero-copy data */
> > const u32 * bitmask;
> > bool plus;
> > + bool labels;
> > };
> >
> > struct nfs4_readdir_res {
> > --
> > 2.18.2
> >
>
> --
> Ondrej Mosnacek
> Software Engineer, Platform Security - SELinux kernel
> Red Hat, Inc.
>
