[Nouveau] [PATCH] nouveau/gem: fix user-after-free in nouveau_gem_new

[Jeremy Cline]

On Tue, May 11, 2021 at 06:35:53PM +0200, Karol Herbst wrote:
> If ttm_bo_init fails it will already call ttm_bo_put, so we don't have to
> do it through nouveau_bo_ref.
> 
> ==================================================================
> BUG: KFENCE: use-after-free write in ttm_bo_put+0x11/0x40 [ttm]
> 
> Use-after-free write at 0x000000004dc4663c (in kfence-#44):
>  ttm_bo_put+0x11/0x40 [ttm]
>  nouveau_gem_new+0xc1/0xf0 [nouveau]
>  nouveau_gem_ioctl_new+0x53/0xf0 [nouveau]
>  drm_ioctl_kernel+0xb2/0x100 [drm]
>  drm_ioctl+0x215/0x390 [drm]
>  nouveau_drm_ioctl+0x55/0xa0 [nouveau]
>  __x64_sys_ioctl+0x83/0xb0
>  do_syscall_64+0x33/0x40
>  entry_SYSCALL_64_after_hwframe+0x44/0xae
> 
> kfence-#44 [0x00000000c0593b31-0x000000002e74122b, size=792, cache=kmalloc-1k] allocated by task 2657:
>  nouveau_bo_alloc+0x63/0x4c0 [nouveau]
>  nouveau_gem_new+0x38/0xf0 [nouveau]
>  nouveau_gem_ioctl_new+0x53/0xf0 [nouveau]
>  drm_ioctl_kernel+0xb2/0x100 [drm]
>  drm_ioctl+0x215/0x390 [drm]
>  nouveau_drm_ioctl+0x55/0xa0 [nouveau]
>  __x64_sys_ioctl+0x83/0xb0
>  do_syscall_64+0x33/0x40
>  entry_SYSCALL_64_after_hwframe+0x44/0xae
> 
> freed by task 2657:
>  ttm_bo_release+0x1cc/0x300 [ttm]
>  ttm_bo_init_reserved+0x2ec/0x300 [ttm]
>  ttm_bo_init+0x5e/0xd0 [ttm]
>  nouveau_bo_init+0xaf/0xc0 [nouveau]
>  nouveau_gem_new+0x7f/0xf0 [nouveau]
>  nouveau_gem_ioctl_new+0x53/0xf0 [nouveau]
>  drm_ioctl_kernel+0xb2/0x100 [drm]
>  drm_ioctl+0x215/0x390 [drm]
>  nouveau_drm_ioctl+0x55/0xa0 [nouveau]
>  __x64_sys_ioctl+0x83/0xb0
>  do_syscall_64+0x33/0x40
>  entry_SYSCALL_64_after_hwframe+0x44/0xae
> 
> Fixes: 019cbd4a4feb3 "drm/nouveau: Initialize GEM object before TTM object"
> Cc: Thierry Reding <treding at nvidia.com>
> Signed-off-by: Karol Herbst <kherbst at redhat.com>
> ---
>  drivers/gpu/drm/nouveau/nouveau_gem.c | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/nouveau/nouveau_gem.c b/drivers/gpu/drm/nouveau/nouveau_gem.c
> index c88cbb85f101..1165ff990fb5 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_gem.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_gem.c
> @@ -212,7 +212,6 @@ nouveau_gem_new(struct nouveau_cli *cli, u64 size, int align, uint32_t domain,
>  
>  	ret = nouveau_bo_init(nvbo, size, align, domain, NULL, NULL);
>  	if (ret) {
> -		nouveau_bo_ref(NULL, &nvbo);
>  		return ret;
>  	}
>  

I submitted a patch for this in the beginning of December, it got
reviewed and it's languished ever since[0]. It's frustrating that these
issues have to get fixed multiple times by multiple developers because
bug fixes (with reviews!) aren't being accepted.

[0] https://lists.freedesktop.org/archives/nouveau/2020-December/037571.html

Anyway, for whatever it's worth:

Reviewed-by: Jeremy Cline <jcline at redhat.com>