From 2dbd9c27eda5cf83aa990266a3355960d860da71 Mon Sep 17 00:00:00 2001 From: Pavel Skripkin Date: Thu, 8 Jul 2021 14:25:18 +0300 Subject: drm/ttm: add missing NULL checks MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit My local syzbot instance hit GPF in ttm_bo_release(). Unfortunately, syzbot didn't produce a reproducer for this, but I found out possible scenario: drm_gem_vram_create() <-- drm_gem_vram_object kzalloced (bo embedded in this object) ttm_bo_init() ttm_bo_init_reserved() ttm_resource_alloc() man->func->alloc() <-- allocation failure ttm_bo_put() ttm_bo_release() ttm_mem_io_free() <-- bo->resource == NULL passed as second argument *GPF* Added NULL check inside ttm_mem_io_free() to prevent reported GPF and make this function NULL save in future. Same problem was in ttm_bo_move_to_lru_tail() as Christian reported. ttm_bo_move_to_lru_tail() is called in ttm_bo_release() and mem pointer can be NULL as well as in ttm_mem_io_free(). Fail log: KASAN: null-ptr-deref in range [0x0000000000000020-0x0000000000000027] ... RIP: 0010:ttm_mem_io_free+0x28/0x170 drivers/gpu/drm/ttm/ttm_bo_util.c:66 .. Call Trace: ttm_bo_release+0xd94/0x10a0 drivers/gpu/drm/ttm/ttm_bo.c:422 kref_put include/linux/kref.h:65 [inline] ttm_bo_put drivers/gpu/drm/ttm/ttm_bo.c:470 [inline] ttm_bo_init_reserved+0x7cb/0x960 drivers/gpu/drm/ttm/ttm_bo.c:1050 ttm_bo_init+0x105/0x270 drivers/gpu/drm/ttm/ttm_bo.c:1074 drm_gem_vram_create+0x332/0x4c0 drivers/gpu/drm/drm_gem_vram_helper.c:228 Fixes: d3116756a710 ("drm/ttm: rename bo->mem and make it a pointer") Signed-off-by: Pavel Skripkin Reviewed-by: Christian König Signed-off-by: Christian König Link: https://patchwork.freedesktop.org/patch/msgid/20210708112518.17271-1-paskripkin@gmail.com --- drivers/gpu/drm/ttm/ttm_bo.c | 3 +++ drivers/gpu/drm/ttm/ttm_bo_util.c | 3 +++ 2 files changed, 6 insertions(+) (limited to 'drivers/gpu/drm/ttm') diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c index 1b950b45cf4b..8d7fd65ccced 100644 --- a/drivers/gpu/drm/ttm/ttm_bo.c +++ b/drivers/gpu/drm/ttm/ttm_bo.c @@ -102,6 +102,9 @@ void ttm_bo_move_to_lru_tail(struct ttm_buffer_object *bo, return; } + if (!mem) + return; + man = ttm_manager_type(bdev, mem->mem_type); list_move_tail(&bo->lru, &man->lru[bo->priority]); diff --git a/drivers/gpu/drm/ttm/ttm_bo_util.c b/drivers/gpu/drm/ttm/ttm_bo_util.c index 2f57f824e6db..763fa6f4e07d 100644 --- a/drivers/gpu/drm/ttm/ttm_bo_util.c +++ b/drivers/gpu/drm/ttm/ttm_bo_util.c @@ -63,6 +63,9 @@ int ttm_mem_io_reserve(struct ttm_device *bdev, void ttm_mem_io_free(struct ttm_device *bdev, struct ttm_resource *mem) { + if (!mem) + return; + if (!mem->bus.offset && !mem->bus.addr) return; -- cgit v1.2.3-59-g8ed1b