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authorScott Mayhew <smayhew@redhat.com>2017-06-05 11:45:04 -0400
committerPaul Moore <paul@paul-moore.com>2017-06-09 16:17:47 -0400
commit0b4d3452b8b4a5309b4445b900e3cec022cca95a (patch)
tree3c758827bc8bab1cd36f9c551840cdae00636e97 /security/selinux
parentb4958c892e02241b9bd121f3397b76225ff6f4a3 (diff)
downloadlinux-0b4d3452b8b4a5309b4445b900e3cec022cca95a.tar.bz2
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 <smayhew@redhat.com> Reviewed-by: Stephen Smalley <sds@tycho.nsa.gov> Tested-by: Stephen Smalley <sds@tycho.nsa.gov> Signed-off-by: Paul Moore <paul@paul-moore.com>
Diffstat (limited to 'security/selinux')
-rw-r--r--security/selinux/hooks.c35
1 files changed, 33 insertions, 2 deletions
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 9926adbd50a9..9cc042df10d1 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 @@ mismatch:
}
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,