[PATCH] drm/vgem: Restore mmap functionality

[Daniel Vetter]

On Fri, Jul 9, 2021 at 1:47 PM Thomas Zimmermann <tzimmermann at suse.de> wrote:
>
> Commit 375cca1cfeb5 ("drm/vgem: Implement mmap as GEM object function")
> accidentally removed the actual mmap functionality from vgem. Restore
> the original implementation and VMA flags.

Ah yes that explains things.

Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch>
>
> Fixes access to unmapped memory:
>
> [  106.591744] BUG: KASAN: vmalloc-out-of-bounds in do_fault+0x38/0x480
> [  106.598154] Read of size 8 at addr ffffffffc10c44a8 by task vgem_basic/1514
> [  106.605173]
> [  106.606678] CPU: 1 PID: 1514 Comm: vgem_basic Tainted: G            E     5.13.0-1-default+ #990
> [  106.615535] Hardware name: Dell Inc. OptiPlex 9020/0N4YC8, BIOS A24 10/24/2018
> [  106.622818] Call Trace:
> [  106.625289]  dump_stack+0xa5/0xdc
> [  106.628642]  print_address_description.constprop.0+0x18/0x100
> [  106.634439]  ? do_fault+0x38/0x480
> [  106.637872]  kasan_report.cold+0x7c/0xd8
> [  106.641834]  ? do_fault+0x38/0x480
> [  106.645274]  do_fault+0x38/0x480
> [  106.648535]  __handle_mm_fault+0x935/0xb00
> [  106.652676]  ? vm_iomap_memory+0xe0/0xe0
> [  106.656634]  ? __lock_release+0x12f/0x4e0
> [  106.660696]  ? count_memcg_event_mm.part.0+0xb9/0x190
> [  106.665799]  handle_mm_fault+0xd0/0x370
> [  106.669675]  do_user_addr_fault+0x2a0/0x8c0
> [  106.673908]  exc_page_fault+0x64/0xf0
> [  106.677604]  ? asm_exc_page_fault+0x8/0x30
> [  106.681739]  asm_exc_page_fault+0x1e/0x30
> [  106.685782] RIP: 0033:0x402e12
> ...
>
> Signed-off-by: Thomas Zimmermann <tzimmermann at suse.de>
> Fixes: 375cca1cfeb5 ("drm/vgem: Implement mmap as GEM object function")
> Cc: Thomas Zimmermann <tzimmermann at suse.de>
> Cc: Christian König <christian.koenig at amd.com>
> Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
> Cc: "Christian König" <christian.koenig at amd.com>
> Cc: Melissa Wen <melissa.srw at gmail.com>
> Cc: Jason Gunthorpe <jgg at ziepe.ca>
> Cc: Gerd Hoffmann <kraxel at redhat.com>
> Cc: Lee Jones <lee.jones at linaro.org>
> ---
>  drivers/gpu/drm/vgem/vgem_drv.c | 11 ++++++++++-
>  1 file changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/vgem/vgem_drv.c b/drivers/gpu/drm/vgem/vgem_drv.c
> index df634aa52638..f50fd10c4fad 100644
> --- a/drivers/gpu/drm/vgem/vgem_drv.c
> +++ b/drivers/gpu/drm/vgem/vgem_drv.c
> @@ -364,8 +364,17 @@ static void vgem_prime_vunmap(struct drm_gem_object *obj, struct dma_buf_map *ma
>
>  static int vgem_prime_mmap(struct drm_gem_object *obj, struct vm_area_struct *vma)
>  {
> +       int ret;
> +
> +       if (!obj->filp)
> +               return -ENODEV;
> +
> +       ret = call_mmap(obj->filp, vma);
> +       if (ret)
> +               return ret;
> +
>         vma_set_file(vma, obj->filp);
> -       vma->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP;
> +       vma->vm_flags |= VM_IO | VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP;
>         vma->vm_page_prot = pgprot_writecombine(vm_get_page_prot(vma->vm_flags));
>         vma->vm_page_prot = pgprot_decrypted(vma->vm_page_prot);
>
> --
> 2.32.0
>


-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch