xen/privcmd: add IOCTL_PRIVCMD_RESTRICT
The purpose if this ioctl is to allow a user of privcmd to restrict its operation such that it will no longer service arbitrary hypercalls via IOCTL_PRIVCMD_HYPERCALL, and will check for a matching domid when servicing IOCTL_PRIVCMD_DM_OP or IOCTL_PRIVCMD_MMAP*. The aim of this is to limit the attack surface for a compromised device model. Signed-off-by: Paul Durrant <paul.durrant@citrix.com> Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>hifive-unleashed-5.1
Paul Durrant
Boris Ostrovsky
parent
ab520be8cd
commit
4610d240d6
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@ -56,16 +56,25 @@ module_param_named(dm_op_buf_max_size, privcmd_dm_op_buf_max_size, uint,
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MODULE_PARM_DESC(dm_op_buf_max_size,
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"Maximum size of a dm_op hypercall buffer");
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struct privcmd_data {
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domid_t domid;
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};
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static int privcmd_vma_range_is_mapped(
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struct vm_area_struct *vma,
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unsigned long addr,
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unsigned long nr_pages);
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static long privcmd_ioctl_hypercall(void __user *udata)
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static long privcmd_ioctl_hypercall(struct file *file, void __user *udata)
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{
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struct privcmd_data *data = file->private_data;
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struct privcmd_hypercall hypercall;
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long ret;
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/* Disallow arbitrary hypercalls if restricted */
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if (data->domid != DOMID_INVALID)
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return -EPERM;
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if (copy_from_user(&hypercall, udata, sizeof(hypercall)))
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return -EFAULT;
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@ -242,8 +251,9 @@ static int mmap_gfn_range(void *data, void *state)
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return 0;
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}
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static long privcmd_ioctl_mmap(void __user *udata)
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static long privcmd_ioctl_mmap(struct file *file, void __user *udata)
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{
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struct privcmd_data *data = file->private_data;
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struct privcmd_mmap mmapcmd;
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struct mm_struct *mm = current->mm;
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struct vm_area_struct *vma;
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@ -258,6 +268,10 @@ static long privcmd_ioctl_mmap(void __user *udata)
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if (copy_from_user(&mmapcmd, udata, sizeof(mmapcmd)))
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return -EFAULT;
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/* If restriction is in place, check the domid matches */
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if (data->domid != DOMID_INVALID && data->domid != mmapcmd.dom)
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return -EPERM;
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rc = gather_array(&pagelist,
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mmapcmd.num, sizeof(struct privcmd_mmap_entry),
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mmapcmd.entry);
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@ -429,8 +443,10 @@ static int alloc_empty_pages(struct vm_area_struct *vma, int numpgs)
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static const struct vm_operations_struct privcmd_vm_ops;
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static long privcmd_ioctl_mmap_batch(void __user *udata, int version)
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static long privcmd_ioctl_mmap_batch(
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struct file *file, void __user *udata, int version)
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{
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struct privcmd_data *data = file->private_data;
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int ret;
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struct privcmd_mmapbatch_v2 m;
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struct mm_struct *mm = current->mm;
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@ -459,6 +475,10 @@ static long privcmd_ioctl_mmap_batch(void __user *udata, int version)
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return -EINVAL;
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}
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/* If restriction is in place, check the domid matches */
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if (data->domid != DOMID_INVALID && data->domid != m.dom)
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return -EPERM;
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nr_pages = DIV_ROUND_UP(m.num, XEN_PFN_PER_PAGE);
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if ((m.num <= 0) || (nr_pages > (LONG_MAX >> PAGE_SHIFT)))
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return -EINVAL;
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@ -603,8 +623,9 @@ static void unlock_pages(struct page *pages[], unsigned int nr_pages)
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}
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}
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static long privcmd_ioctl_dm_op(void __user *udata)
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static long privcmd_ioctl_dm_op(struct file *file, void __user *udata)
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{
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struct privcmd_data *data = file->private_data;
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struct privcmd_dm_op kdata;
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struct privcmd_dm_op_buf *kbufs;
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unsigned int nr_pages = 0;
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@ -616,6 +637,10 @@ static long privcmd_ioctl_dm_op(void __user *udata)
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if (copy_from_user(&kdata, udata, sizeof(kdata)))
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return -EFAULT;
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/* If restriction is in place, check the domid matches */
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if (data->domid != DOMID_INVALID && data->domid != kdata.dom)
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return -EPERM;
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if (kdata.num == 0)
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return 0;
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@ -683,6 +708,23 @@ out:
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return rc;
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}
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static long privcmd_ioctl_restrict(struct file *file, void __user *udata)
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{
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struct privcmd_data *data = file->private_data;
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domid_t dom;
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if (copy_from_user(&dom, udata, sizeof(dom)))
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return -EFAULT;
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/* Set restriction to the specified domain, or check it matches */
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if (data->domid == DOMID_INVALID)
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data->domid = dom;
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else if (data->domid != dom)
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return -EINVAL;
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return 0;
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}
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static long privcmd_ioctl(struct file *file,
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unsigned int cmd, unsigned long data)
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{
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@ -691,23 +733,27 @@ static long privcmd_ioctl(struct file *file,
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switch (cmd) {
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case IOCTL_PRIVCMD_HYPERCALL:
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ret = privcmd_ioctl_hypercall(udata);
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ret = privcmd_ioctl_hypercall(file, udata);
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break;
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case IOCTL_PRIVCMD_MMAP:
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ret = privcmd_ioctl_mmap(udata);
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ret = privcmd_ioctl_mmap(file, udata);
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break;
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case IOCTL_PRIVCMD_MMAPBATCH:
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ret = privcmd_ioctl_mmap_batch(udata, 1);
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ret = privcmd_ioctl_mmap_batch(file, udata, 1);
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break;
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case IOCTL_PRIVCMD_MMAPBATCH_V2:
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ret = privcmd_ioctl_mmap_batch(udata, 2);
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ret = privcmd_ioctl_mmap_batch(file, udata, 2);
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break;
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case IOCTL_PRIVCMD_DM_OP:
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ret = privcmd_ioctl_dm_op(udata);
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ret = privcmd_ioctl_dm_op(file, udata);
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break;
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case IOCTL_PRIVCMD_RESTRICT:
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ret = privcmd_ioctl_restrict(file, udata);
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break;
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default:
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@ -717,6 +763,28 @@ static long privcmd_ioctl(struct file *file,
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return ret;
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}
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static int privcmd_open(struct inode *ino, struct file *file)
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{
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struct privcmd_data *data = kzalloc(sizeof(*data), GFP_KERNEL);
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if (!data)
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return -ENOMEM;
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/* DOMID_INVALID implies no restriction */
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data->domid = DOMID_INVALID;
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file->private_data = data;
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return 0;
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}
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static int privcmd_release(struct inode *ino, struct file *file)
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{
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struct privcmd_data *data = file->private_data;
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kfree(data);
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return 0;
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}
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static void privcmd_close(struct vm_area_struct *vma)
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{
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struct page **pages = vma->vm_private_data;
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@ -785,6 +853,8 @@ static int privcmd_vma_range_is_mapped(
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const struct file_operations xen_privcmd_fops = {
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.owner = THIS_MODULE,
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.unlocked_ioctl = privcmd_ioctl,
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.open = privcmd_open,
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.release = privcmd_release,
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.mmap = privcmd_mmap,
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};
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EXPORT_SYMBOL_GPL(xen_privcmd_fops);
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@ -111,5 +111,7 @@ struct privcmd_dm_op {
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_IOC(_IOC_NONE, 'P', 4, sizeof(struct privcmd_mmapbatch_v2))
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#define IOCTL_PRIVCMD_DM_OP \
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_IOC(_IOC_NONE, 'P', 5, sizeof(struct privcmd_dm_op))
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#define IOCTL_PRIVCMD_RESTRICT \
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_IOC(_IOC_NONE, 'P', 6, sizeof(domid_t))
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#endif /* __LINUX_PUBLIC_PRIVCMD_H__ */
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