Return-Path: Received: from fieldses.org ([173.255.197.46]:33756 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751192AbdFFAqi (ORCPT ); Mon, 5 Jun 2017 20:46:38 -0400 Date: Mon, 5 Jun 2017 20:46:37 -0400 From: "J . Bruce Fields" To: Paul Moore Cc: Scott Mayhew , linux-nfs@vger.kernel.org, Trond Myklebust , selinux@tycho.nsa.gov, Stephen Smalley , Eric Paris , Anna Schumaker Subject: Re: [PATCH v3] security/selinux: allow security_sb_clone_mnt_opts to enable/disable native labeling behavior Message-ID: <20170606004637.GC5789@fieldses.org> References: <20170602130918.gu22wnbd35idaurf@tonberry.usersys.redhat.com> <20170605154504.3659-1-smayhew@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: Sender: linux-nfs-owner@vger.kernel.org List-ID: On Mon, Jun 05, 2017 at 05:21:55PM -0400, Paul Moore wrote: > On Mon, Jun 5, 2017 at 11:45 AM, Scott Mayhew wrote: > > 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. > > > > Signed-off-by: Scott Mayhew > > --- > > fs/nfs/super.c | 17 ++++++++++++++++- > > include/linux/lsm_hooks.h | 4 +++- > > include/linux/security.h | 8 ++++++-- > > security/security.c | 7 +++++-- > > security/selinux/hooks.c | 35 +++++++++++++++++++++++++++++++++-- > > 5 files changed, 63 insertions(+), 8 deletions(-) > > Thanks for sorting this out Scott and Stephen. > > NFS folks, any objections to this patch? If not, I'd like to pull > this into the SELinux tree but I'd like to have an ACK from you before > I do. Looks OK to me, but I think it's Trond or Anna (added to cc) that you want the ACK from. --b. > > > diff --git a/fs/nfs/super.c b/fs/nfs/super.c > > index 2f3822a..b8e0735 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); > > > > diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h > > index 68d91e4..3cc9d77 100644 > > --- a/include/linux/lsm_hooks.h > > +++ b/include/linux/lsm_hooks.h > > @@ -1409,7 +1409,9 @@ union security_list_options { > > unsigned long kern_flags, > > unsigned long *set_kern_flags); > > int (*sb_clone_mnt_opts)(const struct super_block *oldsb, > > - struct super_block *newsb); > > + struct super_block *newsb, > > + unsigned long kern_flags, > > + unsigned long *set_kern_flags); > > int (*sb_parse_opts_str)(char *options, struct security_mnt_opts *opts); > > int (*dentry_init_security)(struct dentry *dentry, int mode, > > const struct qstr *name, void **ctx, > > diff --git a/include/linux/security.h b/include/linux/security.h > > index 549cb82..b44e954 100644 > > --- a/include/linux/security.h > > +++ b/include/linux/security.h > > @@ -249,7 +249,9 @@ int security_sb_set_mnt_opts(struct super_block *sb, > > unsigned long kern_flags, > > unsigned long *set_kern_flags); > > int security_sb_clone_mnt_opts(const struct super_block *oldsb, > > - struct super_block *newsb); > > + struct super_block *newsb, > > + unsigned long kern_flags, > > + unsigned long *set_kern_flags); > > int security_sb_parse_opts_str(char *options, struct security_mnt_opts *opts); > > int security_dentry_init_security(struct dentry *dentry, int mode, > > const struct qstr *name, void **ctx, > > @@ -605,7 +607,9 @@ static inline int security_sb_set_mnt_opts(struct super_block *sb, > > } > > > > static inline int security_sb_clone_mnt_opts(const struct super_block *oldsb, > > - struct super_block *newsb) > > + struct super_block *newsb, > > + unsigned long kern_flags, > > + unsigned long *set_kern_flags) > > { > > return 0; > > } > > diff --git a/security/security.c b/security/security.c > > index 714433e..3013237 100644 > > --- a/security/security.c > > +++ b/security/security.c > > @@ -420,9 +420,12 @@ int security_sb_set_mnt_opts(struct super_block *sb, > > EXPORT_SYMBOL(security_sb_set_mnt_opts); > > > > int security_sb_clone_mnt_opts(const struct super_block *oldsb, > > - struct super_block *newsb) > > + struct super_block *newsb, > > + unsigned long kern_flags, > > + unsigned long *set_kern_flags) > > { > > - return call_int_hook(sb_clone_mnt_opts, 0, oldsb, newsb); > > + return call_int_hook(sb_clone_mnt_opts, 0, oldsb, newsb, > > + kern_flags, set_kern_flags); > > } > > EXPORT_SYMBOL(security_sb_clone_mnt_opts); > > > > diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c > > index 9926adb..9cc042d 100644 > > --- a/security/selinux/hooks.c > > +++ b/security/selinux/hooks.c > > @@ -525,8 +525,16 @@ static int sb_finish_set_opts(struct super_block *sb) > > } > > > > sbsec->flags |= SE_SBINITIALIZED; > > + > > + /* > > + * Explicitly set or clear SBLABEL_MNT. It's not sufficient to simply > > + * leave the flag untouched because sb_clone_mnt_opts might be handing > > + * us a superblock that needs the flag to be cleared. > > + */ > > if (selinux_is_sblabel_mnt(sb)) > > sbsec->flags |= SBLABEL_MNT; > > + else > > + sbsec->flags &= ~SBLABEL_MNT; > > > > /* Initialize the root inode. */ > > rc = inode_doinit_with_dentry(root_inode, root); > > @@ -959,8 +967,11 @@ static int selinux_cmp_sb_context(const struct super_block *oldsb, > > } > > > > static int selinux_sb_clone_mnt_opts(const struct super_block *oldsb, > > - struct super_block *newsb) > > + struct super_block *newsb, > > + unsigned long kern_flags, > > + unsigned long *set_kern_flags) > > { > > + int rc = 0; > > const struct superblock_security_struct *oldsbsec = oldsb->s_security; > > struct superblock_security_struct *newsbsec = newsb->s_security; > > > > @@ -975,6 +986,13 @@ static int selinux_sb_clone_mnt_opts(const struct super_block *oldsb, > > if (!ss_initialized) > > return 0; > > > > + /* > > + * Specifying internal flags without providing a place to > > + * place the results is not allowed. > > + */ > > + if (kern_flags && !set_kern_flags) > > + return -EINVAL; > > + > > /* how can we clone if the old one wasn't set up?? */ > > BUG_ON(!(oldsbsec->flags & SE_SBINITIALIZED)); > > > > @@ -990,6 +1008,18 @@ static int selinux_sb_clone_mnt_opts(const struct super_block *oldsb, > > newsbsec->def_sid = oldsbsec->def_sid; > > newsbsec->behavior = oldsbsec->behavior; > > > > + if (newsbsec->behavior == SECURITY_FS_USE_NATIVE && > > + !(kern_flags & SECURITY_LSM_NATIVE_LABELS) && !set_context) { > > + rc = security_fs_use(newsb); > > + if (rc) > > + goto out; > > + } > > + > > + if (kern_flags & SECURITY_LSM_NATIVE_LABELS && !set_context) { > > + newsbsec->behavior = SECURITY_FS_USE_NATIVE; > > + *set_kern_flags |= SECURITY_LSM_NATIVE_LABELS; > > + } > > + > > if (set_context) { > > u32 sid = oldsbsec->mntpoint_sid; > > > > @@ -1009,8 +1039,9 @@ static int selinux_sb_clone_mnt_opts(const struct super_block *oldsb, > > } > > > > sb_finish_set_opts(newsb); > > +out: > > mutex_unlock(&newsbsec->lock); > > - return 0; > > + return rc; > > } > > > > static int selinux_parse_opts_str(char *options, > > -- > > 2.9.3 > > > > > > -- > paul moore > www.paul-moore.com