nfs: update has_sec_mnt_opts after cloning lsm options from parent

After calling security_sb_clone_mnt_opts() in nfs_get_root(), it's
necessary to copy the value of has_sec_mnt_opts from the cloned
super_block's nfs_server.  Otherwise, calls to nfs_compare_super()
using this super_block may not return the correct result, leading to
mount failures.

For example, mounting an nfs server with the following in /etc/exports:
/export *(rw,insecure,crossmnt,no_root_squash,security_label)
and having /export/scratch on a separate block device.

mount -o v4.2,context=system_u:object_r:root_t:s0 server:/export/test /mnt/test
mount -o v4.2,context=system_u:object_r:swapfile_t:s0 server:/export/scratch /mnt/scratch

The second mount would fail with "mount.nfs: /mnt/scratch is busy or
already mounted or sharecache fail" and "SELinux: mount invalid.  Same
superblock, different security settings for..." would appear in the
syslog.

Also while we're in there, replace several instances of "NFS_SB(s)"
with "server", which was already declared at the top of the
nfs_get_root().

Fixes: ec1ade6a0448 ("nfs: account for selinux security context when deciding to share superblock")
Signed-off-by: Scott Mayhew <smayhew@redhat.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

diff --git a/fs/nfs/getroot.c b/fs/nfs/getroot.c
index aaeeb46..59355c1 100644 (file)
--- a/fs/nfs/getroot.c
+++ b/fs/nfs/getroot.c
@@ -67,7 +67,7 @@ static int nfs_superblock_set_dummy_root(struct super_block *sb, struct inode *i
 int nfs_get_root(struct super_block *s, struct fs_context *fc)
 {
        struct nfs_fs_context *ctx = nfs_fc2context(fc);
-       struct nfs_server *server = NFS_SB(s);
+       struct nfs_server *server = NFS_SB(s), *clone_server;
        struct nfs_fsinfo fsinfo;
        struct dentry *root;
        struct inode *inode;
@@ -127,7 +127,7 @@ int nfs_get_root(struct super_block *s, struct fs_context *fc)
        }
        spin_unlock(&root->d_lock);
        fc->root = root;
-       if (NFS_SB(s)->caps & NFS_CAP_SECURITY_LABEL)
+       if (server->caps & NFS_CAP_SECURITY_LABEL)
                kflags |= SECURITY_LSM_NATIVE_LABELS;
        if (ctx->clone_data.sb) {
                if (d_inode(fc->root)->i_fop != &nfs_dir_operations) {
@@ -137,15 +137,19 @@ int nfs_get_root(struct super_block *s, struct fs_context *fc)
                /* clone lsm security options from the parent to the new sb */
                error = security_sb_clone_mnt_opts(ctx->clone_data.sb,
                                                   s, kflags, &kflags_out);
+               if (error)
+                       goto error_splat_root;
+               clone_server = NFS_SB(ctx->clone_data.sb);
+               server->has_sec_mnt_opts = clone_server->has_sec_mnt_opts;
        } else {
                error = security_sb_set_mnt_opts(s, fc->security,
                                                        kflags, &kflags_out);
        }
        if (error)
                goto error_splat_root;
-       if (NFS_SB(s)->caps & NFS_CAP_SECURITY_LABEL &&
+       if (server->caps & NFS_CAP_SECURITY_LABEL &&
                !(kflags_out & SECURITY_LSM_NATIVE_LABELS))
-               NFS_SB(s)->caps &= ~NFS_CAP_SECURITY_LABEL;
+               server->caps &= ~NFS_CAP_SECURITY_LABEL;
 
        nfs_setsecurity(inode, fsinfo.fattr, fsinfo.fattr->label);
        error = 0;