From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Fri, 2 Jun 2017 09:09:18 -0400 From: Scott Mayhew To: Stephen Smalley Cc: selinux@tycho.nsa.gov, linux-nfs@vger.kernel.org, Paul Moore , Eric Paris , Trond Myklebust , "J . Bruce Fields" Subject: Re: [PATCH v2] security/selinux: allow security_sb_clone_mnt_opts to enable/disable native labeling behavior Message-ID: <20170602130918.gu22wnbd35idaurf@tonberry.usersys.redhat.com> References: <1496341807.27759.15.camel@tycho.nsa.gov> <20170601205947.4917-1-smayhew@redhat.com> <1496408108.19674.1.camel@tycho.nsa.gov> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 In-Reply-To: <1496408108.19674.1.camel@tycho.nsa.gov> List-Id: "Security-Enhanced Linux \(SELinux\) mailing list" List-Post: List-Help: On Fri, 02 Jun 2017, Stephen Smalley wrote: > On Thu, 2017-06-01 at 16:59 -0400, 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            | 18 +++++++++++++++++- > >  include/linux/lsm_hooks.h |  4 +++- > >  include/linux/security.h  |  8 ++++++-- > >  security/security.c       |  7 +++++-- > >  security/selinux/hooks.c  | 35 +++++++++++++++++++++++++++++++++-- > >  5 files changed, 64 insertions(+), 8 deletions(-) > > What tree is this against? Doesn't apply cleanly on selinux #next. It's against Linus' mainline tree. > > > > > diff --git a/fs/nfs/super.c b/fs/nfs/super.c > > index 2f3822a..ffded39 100644 > > --- a/fs/nfs/super.c > > +++ b/fs/nfs/super.c > > @@ -2544,10 +2544,26 @@ 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 error; > > This can just be return 0, right? Yes. > > > + > >  } > >  EXPORT_SYMBOL_GPL(nfs_clone_sb_security); > >   > > diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h > > index 080f34e..2f54bfb 100644 > > --- a/include/linux/lsm_hooks.h > > +++ b/include/linux/lsm_hooks.h > > @@ -1388,7 +1388,9 @@ 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 af675b5..a55ae9c 100644 > > --- a/include/linux/security.h > > +++ b/include/linux/security.h > > @@ -240,7 +240,9 @@ 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, > > @@ -581,7 +583,9 @@ 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 b9fea39..7b70ea2 100644 > > --- a/security/security.c > > +++ b/security/security.c > > @@ -380,9 +380,12 @@ 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 e67a526..d8d5d35 100644 > > --- a/security/selinux/hooks.c > > +++ b/security/selinux/hooks.c > > @@ -529,8 +529,16 @@ static int sb_finish_set_opts(struct super_block > > *sb) > >          sb->s_id, sb->s_type->name); > >   > >   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); > > @@ -963,8 +971,11 @@ 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; > >   > > @@ -979,6 +990,13 @@ 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)); > >   > > @@ -994,6 +1012,18 @@ 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; > >   > > @@ -1013,8 +1043,9 @@ 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,