On 23/02/2021 15:51, Neil Roberts wrote:
When a buffer is madvised as not needed and then purged, any attempts to access the buffer from user-space should cause a bus fault. This patch adds a check for that.
Cc: stable@vger.kernel.org Fixes: 17acb9f35ed7 ("drm/shmem: Add madvise state and purge helpers") Signed-off-by: Neil Roberts nroberts@igalia.com
Reviewed-by: Steven Price steven.price@arm.com
drivers/gpu/drm/drm_gem_shmem_helper.c | 18 ++++++++++++++---- 1 file changed, 14 insertions(+), 4 deletions(-)
diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c index 9825c378dfa6..b26139b1dc35 100644 --- a/drivers/gpu/drm/drm_gem_shmem_helper.c +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c @@ -525,14 +525,24 @@ static vm_fault_t drm_gem_shmem_fault(struct vm_fault *vmf) struct drm_gem_object *obj = vma->vm_private_data; struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj); loff_t num_pages = obj->size >> PAGE_SHIFT;
- vm_fault_t ret; struct page *page;
- if (vmf->pgoff >= num_pages || WARN_ON_ONCE(!shmem->pages))
return VM_FAULT_SIGBUS;
- mutex_lock(&shmem->pages_lock);
- if (vmf->pgoff >= num_pages ||
WARN_ON_ONCE(!shmem->pages) ||shmem->madv < 0) {ret = VM_FAULT_SIGBUS;- } else {
page = shmem->pages[vmf->pgoff];
- page = shmem->pages[vmf->pgoff];
ret = vmf_insert_page(vma, vmf->address, page);- }
- return vmf_insert_page(vma, vmf->address, page);
- mutex_unlock(&shmem->pages_lock);
- return ret; }
static void drm_gem_shmem_vm_open(struct vm_area_struct *vma)