On Mon, 2017-06-05 at 11:45 -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 <smayhew@xxxxxxxxxx> Reviewed-by: Stephen Smalley <sds@xxxxxxxxxxxxx> Tested-by: Stephen Smalley <sds@xxxxxxxxxxxxx> Resolves: https://github.com/SELinuxProject/selinux-kernel/issues/35 > --- > 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(-) > > 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, -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
