SELinux: implement the new sb_remount LSM hook
For SELinux we do not allow security information to change during a remount
operation. Thus this hook simply strips the security module options from
the data and verifies that those are the same options as exist on the
current superblock.
Signed-off-by: Eric Paris <eparis@redhat.com>
Reviewed-by: James Morris <jmorris@namei.org>
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 3decf07..f2f3cf2 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -2363,6 +2363,91 @@
return rc;
}
+static int selinux_sb_remount(struct super_block *sb, void *data)
+{
+ int rc, i, *flags;
+ struct security_mnt_opts opts;
+ char *secdata, **mount_options;
+ struct superblock_security_struct *sbsec = sb->s_security;
+
+ if (!(sbsec->flags & SE_SBINITIALIZED))
+ return 0;
+
+ if (!data)
+ return 0;
+
+ if (sb->s_type->fs_flags & FS_BINARY_MOUNTDATA)
+ return 0;
+
+ security_init_mnt_opts(&opts);
+ secdata = alloc_secdata();
+ if (!secdata)
+ return -ENOMEM;
+ rc = selinux_sb_copy_data(data, secdata);
+ if (rc)
+ goto out_free_secdata;
+
+ rc = selinux_parse_opts_str(secdata, &opts);
+ if (rc)
+ goto out_free_secdata;
+
+ mount_options = opts.mnt_opts;
+ flags = opts.mnt_opts_flags;
+
+ for (i = 0; i < opts.num_mnt_opts; i++) {
+ u32 sid;
+ size_t len;
+
+ if (flags[i] == SE_SBLABELSUPP)
+ continue;
+ len = strlen(mount_options[i]);
+ rc = security_context_to_sid(mount_options[i], len, &sid);
+ if (rc) {
+ printk(KERN_WARNING "SELinux: security_context_to_sid"
+ "(%s) failed for (dev %s, type %s) errno=%d\n",
+ mount_options[i], sb->s_id, sb->s_type->name, rc);
+ goto out_free_opts;
+ }
+ rc = -EINVAL;
+ switch (flags[i]) {
+ case FSCONTEXT_MNT:
+ if (bad_option(sbsec, FSCONTEXT_MNT, sbsec->sid, sid))
+ goto out_bad_option;
+ break;
+ case CONTEXT_MNT:
+ if (bad_option(sbsec, CONTEXT_MNT, sbsec->mntpoint_sid, sid))
+ goto out_bad_option;
+ break;
+ case ROOTCONTEXT_MNT: {
+ struct inode_security_struct *root_isec;
+ root_isec = sb->s_root->d_inode->i_security;
+
+ if (bad_option(sbsec, ROOTCONTEXT_MNT, root_isec->sid, sid))
+ goto out_bad_option;
+ break;
+ }
+ case DEFCONTEXT_MNT:
+ if (bad_option(sbsec, DEFCONTEXT_MNT, sbsec->def_sid, sid))
+ goto out_bad_option;
+ break;
+ default:
+ goto out_free_opts;
+ }
+ }
+
+ rc = 0;
+out_free_opts:
+ security_free_mnt_opts(&opts);
+out_free_secdata:
+ free_secdata(secdata);
+ return rc;
+out_bad_option:
+ printk(KERN_WARNING "SELinux: unable to change security options "
+ "during remount (dev %s, type=%s)\n", sb->s_id,
+ sb->s_type->name);
+ goto out_free_opts;
+}
+
static int selinux_sb_kern_mount(struct super_block *sb, int flags, void *data)
{
const struct cred *cred = current_cred();
@@ -5356,6 +5441,7 @@
.sb_alloc_security = selinux_sb_alloc_security,
.sb_free_security = selinux_sb_free_security,
.sb_copy_data = selinux_sb_copy_data,
+ .sb_remount = selinux_sb_remount,
.sb_kern_mount = selinux_sb_kern_mount,
.sb_show_options = selinux_sb_show_options,
.sb_statfs = selinux_sb_statfs,