From d611b4a0907cece060699f2fd347c492451cd2aa Mon Sep 17 00:00:00 2001 From: Neil Roberts Date: Tue, 23 Feb 2021 16:51:24 +0100 Subject: drm/shmem-helper: Check for purged buffers in fault handler 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 Reviewed-by: Steven Price Signed-off-by: Steven Price Link: https://patchwork.freedesktop.org/patch/msgid/20210223155125.199577-2-nroberts@igalia.com Signed-off-by: Maarten Lankhorst --- drivers/gpu/drm/drm_gem_shmem_helper.c | 18 ++++++++++++++---- 1 file changed, 14 insertions(+), 4 deletions(-) (limited to 'drivers') 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) -- cgit v1.2.3