Re: [PATCH v4] drm/radeon/radeon_kms: Fix a NULL pointer dereference in radeon_driver_open_kms()

Am 01.12.21 um 04:22 schrieb Zhou Qingyang:

In radeon_driver_open_kms(), radeon_vm_bo_add() is assigned to vm->ib_bo_va and passes and used in radeon_vm_bo_set_addr(). In radeon_vm_bo_set_addr(), there is a dereference of vm->ib_bo_va, which could lead to a NULL pointer dereference on failure of radeon_vm_bo_add().

Fix this bug by adding a check of vm->ib_bo_va.

This bug was found by a static analyzer. The analysis employs differential checking to identify inconsistent security operations (e.g., checks or kfrees) between two code paths and confirms that the inconsistent operations are not recovered in the current function or the callers, so they constitute bugs.

Note that, as a bug found by static analysis, it can be a false positive or hard to trigger. Multiple researchers have cross-reviewed the bug.

Builds with CONFIG_DRM_RADEON=m show no new warnings, and our static analyzer no longer warns about this code.

Fixes: cc9e67e3d700 ("drm/radeon: fix VM IB handling") Reported-by: kernel test robot lkp@intel.com Signed-off-by: Zhou Qingyang zhou1615@umn.edu

---

Changes in v2:

• Initialize the variables to silence warning

What warning do you get? Double checking the code that shouldn't be necessary and is usually rather frowned upon.

Thanks, Christian.

Changes in v3:

• Fix the bug that good case will also be freed
• Improve code style

Changes in v2:

• Improve the error handling into goto style

drivers/gpu/drm/radeon/radeon_kms.c | 37 ++++++++++++++++------------- 1 file changed, 20 insertions(+), 17 deletions(-)

diff --git a/drivers/gpu/drm/radeon/radeon_kms.c b/drivers/gpu/drm/radeon/radeon_kms.c index 482fb0ae6cb5..9d0f840286a1 100644 --- a/drivers/gpu/drm/radeon/radeon_kms.c +++ b/drivers/gpu/drm/radeon/radeon_kms.c @@ -648,7 +648,9 @@ void radeon_driver_lastclose_kms(struct drm_device *dev) int radeon_driver_open_kms(struct drm_device *dev, struct drm_file *file_priv) { struct radeon_device *rdev = dev->dev_private;

• int r;

• struct radeon_fpriv *fpriv = NULL;

• struct radeon_vm *vm = NULL;

• int r = 0;

  file_priv->driver_priv = NULL;

@@ -660,8 +662,6 @@ int radeon_driver_open_kms(struct drm_device *dev, struct drm_file *file_priv)

/* new gpu have virtual address space support */ if (rdev->family >= CHIP_CAYMAN) {

• struct radeon_fpriv *fpriv;
  

• struct radeon_vm *vm;
  
  

  fpriv = kzalloc(sizeof(*fpriv), GFP_KERNEL); if (unlikely(!fpriv)) {

@@ -672,35 +672,38 @@ int radeon_driver_open_kms(struct drm_device *dev, struct drm_file *file_priv) if (rdev->accel_working) { vm = &fpriv->vm; r = radeon_vm_init(rdev, vm);

• 	if (r) {
  

• 		kfree(fpriv);
  

• 		goto out_suspend;
  

• 	}
  

• 	if (r)
  

• 		goto out_fpriv;
  
  r = radeon_bo_reserve(rdev->ring_tmp_bo.bo, false);
  

• 	if (r) {
  

• 		radeon_vm_fini(rdev, vm);
  

• 		kfree(fpriv);
  

• 		goto out_suspend;
  

• 	}
  

• 	if (r)
  

• 		goto out_vm_fini;
  
  /* map the ib pool buffer read only into
   * virtual address space */
  vm->ib_bo_va = radeon_vm_bo_add(rdev, vm,
  				rdev->ring_tmp_bo.bo);
  

• 	if (!vm->ib_bo_va) {
  

• 		r = -ENOMEM;
  

• 		goto out_vm_fini;
  

• 	}
  

• r = radeon_vm_bo_set_addr(rdev, vm->ib_bo_va,
  			  RADEON_VA_IB_OFFSET,
  			  RADEON_VM_PAGE_READABLE |
  			  RADEON_VM_PAGE_SNOOPED);
  

• 	if (r) {
  

• 		radeon_vm_fini(rdev, vm);
  

• 		kfree(fpriv);
  

• 		goto out_suspend;
  

• 	}
  

• 	if (r)
  

• 		goto out_vm_fini;
  

  } file_priv->driver_priv = fpriv; }

+out_vm_fini:

• if (r)

• radeon_vm_fini(rdev, vm);
  

+out_fpriv:

• if (r)

• kfree(fpriv);
  

  out_suspend: pm_runtime_mark_last_busy(dev->dev); pm_runtime_put_autosuspend(dev->dev);