From 0b4d3452b8b4a5309b4445b900e3cec022cca95a Mon Sep 17 00:00:00 2001 From: Scott Mayhew Date: Mon, 5 Jun 2017 11:45:04 -0400 Subject: security/selinux: allow security_sb_clone_mnt_opts to enable/disable native labeling behavior When an NFSv4 client performs a mount operation, it first mounts the NFSv4 root and then does path walk to the exported path and performs a submount on that, cloning the security mount options from the root's superblock to the submount's superblock in the process. Unless the NFS server has an explicit fsid=0 export with the "security_label" option, the NFSv4 root superblock will not have SBLABEL_MNT set, and neither will the submount superblock after cloning the security mount options. As a result, setxattr's of security labels over NFSv4.2 will fail. In a similar fashion, NFSv4.2 mounts mounted with the context= mount option will not show the correct labels because the nfs_server->caps flags of the cloned superblock will still have NFS_CAP_SECURITY_LABEL set. Allowing the NFSv4 client to enable or disable SECURITY_LSM_NATIVE_LABELS behavior will ensure that the SBLABEL_MNT flag has the correct value when the client traverses from an exported path without the "security_label" option to one with the "security_label" option and vice versa. Similarly, checking to see if SECURITY_LSM_NATIVE_LABELS is set upon return from security_sb_clone_mnt_opts() and clearing NFS_CAP_SECURITY_LABEL if necessary will allow the correct labels to be displayed for NFSv4.2 mounts mounted with the context= mount option. Resolves: https://github.com/SELinuxProject/selinux-kernel/issues/35 Signed-off-by: Scott Mayhew Reviewed-by: Stephen Smalley Tested-by: Stephen Smalley Signed-off-by: Paul Moore --- fs/nfs/super.c | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-) (limited to 'fs/nfs/super.c') diff --git a/fs/nfs/super.c b/fs/nfs/super.c index 2f3822a4a7d5..b8e073546507 100644 --- a/fs/nfs/super.c +++ b/fs/nfs/super.c @@ -2544,10 +2544,25 @@ EXPORT_SYMBOL_GPL(nfs_set_sb_security); int nfs_clone_sb_security(struct super_block *s, struct dentry *mntroot, struct nfs_mount_info *mount_info) { + int error; + unsigned long kflags = 0, kflags_out = 0; + /* clone any lsm security options from the parent to the new sb */ if (d_inode(mntroot)->i_op != NFS_SB(s)->nfs_client->rpc_ops->dir_inode_ops) return -ESTALE; - return security_sb_clone_mnt_opts(mount_info->cloned->sb, s); + + if (NFS_SB(s)->caps & NFS_CAP_SECURITY_LABEL) + kflags |= SECURITY_LSM_NATIVE_LABELS; + + error = security_sb_clone_mnt_opts(mount_info->cloned->sb, s, kflags, + &kflags_out); + if (error) + return error; + + if (NFS_SB(s)->caps & NFS_CAP_SECURITY_LABEL && + !(kflags_out & SECURITY_LSM_NATIVE_LABELS)) + NFS_SB(s)->caps &= ~NFS_CAP_SECURITY_LABEL; + return 0; } EXPORT_SYMBOL_GPL(nfs_clone_sb_security); -- cgit v1.2.3