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),
> 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.
