On 27.02.2017 20:54, Jean-Philippe Brucker wrote:
Let the process that owns the device create an address space bond on
behalf of another process. We add a pid argument to the BIND_TASK ioctl,
allowing the caller to bind a foreign task. The expected program flow in
this case is:
* Process A creates the VFIO context and initializes the device.
* Process B asks A to bind its address space.
* Process A issues an ioctl to the VFIO device fd with BIND_TASK(pid).
It may communicate the given PASID back to process B or keep track of it
internally.
* Process B asks A to perform transactions on its virtual address.
* Process A launches transaction tagged with the given PASID.
Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker@xxxxxxx>
---
drivers/vfio/vfio.c | 35 +++++++++++++++++++++++++++++++++--
include/uapi/linux/vfio.h | 15 +++++++++++++++
2 files changed, 48 insertions(+), 2 deletions(-)
diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index c4505d8f4c61..ecc5d07e3dbb 100644
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -26,6 +26,7 @@
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/pci.h>
+#include <linux/ptrace.h>
#include <linux/rwsem.h>
#include <linux/sched.h>
#include <linux/slab.h>
@@ -1660,7 +1661,7 @@ static long vfio_svm_ioctl(struct vfio_device *device, unsigned int cmd,
struct vfio_device_svm svm;
struct vfio_task *vfio_task;
- minsz = offsetofend(struct vfio_device_svm, pasid);
+ minsz = offsetofend(struct vfio_device_svm, pid);
if (copy_from_user(&svm, (void __user *)arg, minsz))
return -EFAULT;
@@ -1669,9 +1670,39 @@ static long vfio_svm_ioctl(struct vfio_device *device, unsigned int cmd,
return -EINVAL;
if (cmd == VFIO_DEVICE_BIND_TASK) {
- struct task_struct *task = current;
+ struct mm_struct *mm;
+ struct task_struct *task;
+
+ if (svm.flags & ~VFIO_SVM_PID)
+ return -EINVAL;
+
+ if (svm.flags & VFIO_SVM_PID) {
+ rcu_read_lock();
+ task = find_task_by_vpid(svm.pid);
+ if (task)
+ get_task_struct(task);
+ rcu_read_unlock();
+ if (!task)
+ return -ESRCH;
+
+ /*
+ * Ensure process has RW access on the task's mm
+ * FIXME:
+ * - I think this ought to be in the IOMMU API
+ * - I'm assuming permission is never revoked during the
+ * task's lifetime. Might be mistaken.
+ */
+ mm = mm_access(task, PTRACE_MODE_ATTACH_REALCREDS);
+ if (!mm || IS_ERR(mm))
I know this is RFC patch but considering we will keep this as is, we
need here:
+put_task_struct(task);
+ return IS_ERR(mm) ? PTR_ERR(mm) : -ESRCH;
+ mmput(mm);
+ } else {
+ get_task_struct(current);
+ task = current;
+ }
ret = iommu_bind_task(device->dev, task, &svm.pasid, 0, NULL);
+ put_task_struct(task);
if (ret)
return ret;
Thanks,
Tomasz
