From: Jia Yang <jiayang5@xxxxxxxxxx> [ Upstream commit da62cb7230f0871c30dc9789071f63229158d261 ] I got a use-after-free report when doing some fuzz test: If ttm_bo_init() fails, the "gbo" and "gbo->bo.base" will be freed by ttm_buffer_object_destroy() in ttm_bo_init(). But then drm_gem_vram_create() and drm_gem_vram_init() will free "gbo" and "gbo->bo.base" again. BUG: KMSAN: use-after-free in drm_vma_offset_remove+0xb3/0x150 CPU: 0 PID: 24282 Comm: syz-executor.1 Tainted: G B W 5.7.0-rc4-msan #2 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014 Call Trace: __dump_stack dump_stack+0x1c9/0x220 kmsan_report+0xf7/0x1e0 __msan_warning+0x58/0xa0 drm_vma_offset_remove+0xb3/0x150 drm_gem_free_mmap_offset drm_gem_object_release+0x159/0x180 drm_gem_vram_init drm_gem_vram_create+0x7c5/0x990 drm_gem_vram_fill_create_dumb drm_gem_vram_driver_dumb_create+0x238/0x590 drm_mode_create_dumb drm_mode_create_dumb_ioctl+0x41d/0x450 drm_ioctl_kernel+0x5a4/0x710 drm_ioctl+0xc6f/0x1240 vfs_ioctl ksys_ioctl __do_sys_ioctl __se_sys_ioctl+0x2e9/0x410 __x64_sys_ioctl+0x4a/0x70 do_syscall_64+0xb8/0x160 entry_SYSCALL_64_after_hwframe+0x44/0xa9 RIP: 0033:0x4689b9 Code: fd e0 fa ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 cb e0 fa ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007f368fa4dc98 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 000000000076bf00 RCX: 00000000004689b9 RDX: 0000000020000240 RSI: 00000000c02064b2 RDI: 0000000000000003 RBP: 0000000000000004 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00000000004d17e0 R14: 00007f368fa4e6d4 R15: 000000000076bf0c Uninit was created at: kmsan_save_stack_with_flags kmsan_internal_poison_shadow+0x66/0xd0 kmsan_slab_free+0x6e/0xb0 slab_free_freelist_hook slab_free kfree+0x571/0x30a0 drm_gem_vram_destroy ttm_buffer_object_destroy+0xc8/0x130 ttm_bo_release kref_put ttm_bo_put+0x117d/0x23e0 ttm_bo_init_reserved+0x11c0/0x11d0 ttm_bo_init+0x289/0x3f0 drm_gem_vram_init drm_gem_vram_create+0x775/0x990 drm_gem_vram_fill_create_dumb drm_gem_vram_driver_dumb_create+0x238/0x590 drm_mode_create_dumb drm_mode_create_dumb_ioctl+0x41d/0x450 drm_ioctl_kernel+0x5a4/0x710 drm_ioctl+0xc6f/0x1240 vfs_ioctl ksys_ioctl __do_sys_ioctl __se_sys_ioctl+0x2e9/0x410 __x64_sys_ioctl+0x4a/0x70 do_syscall_64+0xb8/0x160 entry_SYSCALL_64_after_hwframe+0x44/0xa9 If ttm_bo_init() fails, the "gbo" will be freed by ttm_buffer_object_destroy() in ttm_bo_init(). But then drm_gem_vram_create() and drm_gem_vram_init() will free "gbo" again. Reported-by: Hulk Robot <hulkci@xxxxxxxxxx> Reported-by: butt3rflyh4ck <butterflyhuangxx@xxxxxxxxx> Signed-off-by: Jia Yang <jiayang5@xxxxxxxxxx> Signed-off-by: Thomas Zimmermann <tzimmermann@xxxxxxx> Reviewed-by: Thomas Zimmermann <tzimmermann@xxxxxxx> Link: https://patchwork.freedesktop.org/patch/msgid/20200714083238.28479-2-tzimmermann@xxxxxxx Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- drivers/gpu/drm/drm_gem_vram_helper.c | 28 +++++++++++++++------------ 1 file changed, 16 insertions(+), 12 deletions(-) diff --git a/drivers/gpu/drm/drm_gem_vram_helper.c b/drivers/gpu/drm/drm_gem_vram_helper.c index 8b2d5c945c95c..1d85af9a481ac 100644 --- a/drivers/gpu/drm/drm_gem_vram_helper.c +++ b/drivers/gpu/drm/drm_gem_vram_helper.c @@ -175,6 +175,10 @@ static void drm_gem_vram_placement(struct drm_gem_vram_object *gbo, } } +/* + * Note that on error, drm_gem_vram_init will free the buffer object. + */ + static int drm_gem_vram_init(struct drm_device *dev, struct drm_gem_vram_object *gbo, size_t size, unsigned long pg_align) @@ -184,15 +188,19 @@ static int drm_gem_vram_init(struct drm_device *dev, int ret; size_t acc_size; - if (WARN_ONCE(!vmm, "VRAM MM not initialized")) + if (WARN_ONCE(!vmm, "VRAM MM not initialized")) { + kfree(gbo); return -EINVAL; + } bdev = &vmm->bdev; gbo->bo.base.funcs = &drm_gem_vram_object_funcs; ret = drm_gem_object_init(dev, &gbo->bo.base, size); - if (ret) + if (ret) { + kfree(gbo); return ret; + } acc_size = ttm_bo_dma_acc_size(bdev, size, sizeof(*gbo)); @@ -203,13 +211,13 @@ static int drm_gem_vram_init(struct drm_device *dev, &gbo->placement, pg_align, false, acc_size, NULL, NULL, ttm_buffer_object_destroy); if (ret) - goto err_drm_gem_object_release; + /* + * A failing ttm_bo_init will call ttm_buffer_object_destroy + * to release gbo->bo.base and kfree gbo. + */ + return ret; return 0; - -err_drm_gem_object_release: - drm_gem_object_release(&gbo->bo.base); - return ret; } /** @@ -243,13 +251,9 @@ struct drm_gem_vram_object *drm_gem_vram_create(struct drm_device *dev, ret = drm_gem_vram_init(dev, gbo, size, pg_align); if (ret < 0) - goto err_kfree; + return ERR_PTR(ret); return gbo; - -err_kfree: - kfree(gbo); - return ERR_PTR(ret); } EXPORT_SYMBOL(drm_gem_vram_create); -- 2.25.1
