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>
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@ -2363,6 +2363,91 @@ out:
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return rc;
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}
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static int selinux_sb_remount(struct super_block *sb, void *data)
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{
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int rc, i, *flags;
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struct security_mnt_opts opts;
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char *secdata, **mount_options;
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struct superblock_security_struct *sbsec = sb->s_security;
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if (!(sbsec->flags & SE_SBINITIALIZED))
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return 0;
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if (!data)
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return 0;
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if (sb->s_type->fs_flags & FS_BINARY_MOUNTDATA)
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return 0;
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security_init_mnt_opts(&opts);
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secdata = alloc_secdata();
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if (!secdata)
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return -ENOMEM;
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rc = selinux_sb_copy_data(data, secdata);
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if (rc)
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goto out_free_secdata;
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rc = selinux_parse_opts_str(secdata, &opts);
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if (rc)
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goto out_free_secdata;
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mount_options = opts.mnt_opts;
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flags = opts.mnt_opts_flags;
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for (i = 0; i < opts.num_mnt_opts; i++) {
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u32 sid;
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size_t len;
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if (flags[i] == SE_SBLABELSUPP)
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continue;
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len = strlen(mount_options[i]);
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rc = security_context_to_sid(mount_options[i], len, &sid);
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if (rc) {
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printk(KERN_WARNING "SELinux: security_context_to_sid"
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"(%s) failed for (dev %s, type %s) errno=%d\n",
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mount_options[i], sb->s_id, sb->s_type->name, rc);
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goto out_free_opts;
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}
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rc = -EINVAL;
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switch (flags[i]) {
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case FSCONTEXT_MNT:
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if (bad_option(sbsec, FSCONTEXT_MNT, sbsec->sid, sid))
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goto out_bad_option;
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break;
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case CONTEXT_MNT:
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if (bad_option(sbsec, CONTEXT_MNT, sbsec->mntpoint_sid, sid))
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goto out_bad_option;
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break;
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case ROOTCONTEXT_MNT: {
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struct inode_security_struct *root_isec;
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root_isec = sb->s_root->d_inode->i_security;
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if (bad_option(sbsec, ROOTCONTEXT_MNT, root_isec->sid, sid))
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goto out_bad_option;
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break;
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}
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case DEFCONTEXT_MNT:
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if (bad_option(sbsec, DEFCONTEXT_MNT, sbsec->def_sid, sid))
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goto out_bad_option;
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break;
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default:
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goto out_free_opts;
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}
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}
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rc = 0;
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out_free_opts:
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security_free_mnt_opts(&opts);
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out_free_secdata:
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free_secdata(secdata);
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return rc;
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out_bad_option:
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printk(KERN_WARNING "SELinux: unable to change security options "
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"during remount (dev %s, type=%s)\n", sb->s_id,
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sb->s_type->name);
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goto out_free_opts;
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}
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static int selinux_sb_kern_mount(struct super_block *sb, int flags, void *data)
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{
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const struct cred *cred = current_cred();
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@ -5356,6 +5441,7 @@ static struct security_operations selinux_ops = {
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.sb_alloc_security = selinux_sb_alloc_security,
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.sb_free_security = selinux_sb_free_security,
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.sb_copy_data = selinux_sb_copy_data,
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.sb_remount = selinux_sb_remount,
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.sb_kern_mount = selinux_sb_kern_mount,
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.sb_show_options = selinux_sb_show_options,
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.sb_statfs = selinux_sb_statfs,
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