[PATCH] drm: Add the mutex protection in drm_do_vm_fault.

[Jun Chen]

There are no mutex protection for the dev->map_hash while calling
the drm_ht_find_item in the function drm_do_vm_fault. So try to
mutex firstly and then find the list for using to avoid this race
condition.

Signed-off-by: Chen Jun <jun.d.c...@intel.com>
---
 drivers/gpu/drm/drm_vm.c |   11 +++++++++--
 1 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/drm_vm.c b/drivers/gpu/drm/drm_vm.c
index b5c5af7..1d95221 100644
--- a/drivers/gpu/drm/drm_vm.c
+++ b/drivers/gpu/drm/drm_vm.c
@@ -107,8 +107,11 @@ static int drm_do_vm_fault(struct vm_area_struct *vma, 
struct vm_fault *vmf)
        if (!dev->agp || !dev->agp->cant_use_aperture)
                goto vm_fault_error;
 
-       if (drm_ht_find_item(&dev->map_hash, vma->vm_pgoff, &hash))
+       mutex_lock(&dev->struct_mutex);
+       if (drm_ht_find_item(&dev->map_hash, vma->vm_pgoff, &hash)) {
+               mutex_unlock(&dev->struct_mutex);
                goto vm_fault_error;
+       }
 
        r_list = drm_hash_entry(hash, struct drm_map_list, hash);
        map = r_list->map;
@@ -140,8 +143,10 @@ static int drm_do_vm_fault(struct vm_area_struct *vma, 
struct vm_fault *vmf)
                                break;
                }
 
-               if (&agpmem->head == &dev->agp->memory)
+               if (&agpmem->head == &dev->agp->memory) {
+                       mutex_unlock(&dev->struct_mutex);
                        goto vm_fault_error;
+               }
 
                /*
                 * Get the page, inc the use count, and return it
@@ -151,6 +156,7 @@ static int drm_do_vm_fault(struct vm_area_struct *vma, 
struct vm_fault *vmf)
                get_page(page);
                vmf->page = page;
 
+               mutex_unlock(&dev->struct_mutex);
                DRM_DEBUG
                    ("baddr = 0x%llx page = 0x%p, offset = 0x%llx, count=%d\n",
                     (unsigned long long)baddr,
@@ -159,6 +165,7 @@ static int drm_do_vm_fault(struct vm_area_struct *vma, 
struct vm_fault *vmf)
                     page_count(page));
                return 0;
        }
+       mutex_unlock(&dev->struct_mutex);
 vm_fault_error:
        return VM_FAULT_SIGBUS; /* Disallow mremap */
 }
-- 
1.7.4.1



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