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On 2020/6/20 14:21, Jia Yang wrote:
> 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>
> Signed-off-by: Jia Yang <jiayang5@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 8b2d5c945c95..1d85af9a481a 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);
>
>
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