Re: [PATCH] drm/tegra: Check offsets of a submitted command buffer and of relocations

[Mikko Perttunen <cyndis-/1wQRMveznE@public.gmane.org>]

On 14.05.2017 23:47, Dmitry Osipenko wrote:
> If commands buffer claims a number of words that is higher than its BO can
> fit, a kernel OOPS will be fired on the out-of-bounds BO access. This was
> triggered by an opentegra Xorg driver that erroneously pushed too many
> commands to the pushbuf. The CMDA commands buffer address is 4 bytes
> aligned, so check the alignment as well.
>
> Add a sanity check for the relocations in a same way.
>
> [   46.829393] Unable to handle kernel paging request at virtual address f09b2000
> ...
> [<c04a3ba4>] (host1x_job_pin) from [<c04dfcd0>] (tegra_drm_submit+0x474/0x510)
> [<c04dfcd0>] (tegra_drm_submit) from [<c04deea0>] (tegra_submit+0x50/0x6c)
> [<c04deea0>] (tegra_submit) from [<c04c07c0>] (drm_ioctl+0x1e4/0x3ec)
> [<c04c07c0>] (drm_ioctl) from [<c02541a0>] (do_vfs_ioctl+0x9c/0x8e4)
> [<c02541a0>] (do_vfs_ioctl) from [<c0254a1c>] (SyS_ioctl+0x34/0x5c)
> [<c0254a1c>] (SyS_ioctl) from [<c0107640>] (ret_fast_syscall+0x0/0x3c)
>
> Signed-off-by: Dmitry Osipenko <digetx-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> Reviewed-by: Erik Faye-Lund <kusmabite-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> ---
>  drivers/gpu/drm/tegra/drm.c | 30 ++++++++++++++++++++++++++++++
>  drivers/gpu/drm/tegra/gem.c |  5 -----
>  drivers/gpu/drm/tegra/gem.h |  5 +++++
>  3 files changed, 35 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/tegra/drm.c b/drivers/gpu/drm/tegra/drm.c
> index 768750226452..c5844a065681 100644
> --- a/drivers/gpu/drm/tegra/drm.c
> +++ b/drivers/gpu/drm/tegra/drm.c
> @@ -362,6 +362,8 @@ int tegra_drm_submit(struct tegra_drm_context *context,
>  	while (num_cmdbufs) {
>  		struct drm_tegra_cmdbuf cmdbuf;
>  		struct host1x_bo *bo;
> +		struct tegra_bo *obj;
> +		u64 offset;
>
>  		if (copy_from_user(&cmdbuf, cmdbufs, sizeof(cmdbuf))) {
>  			err = -EFAULT;
> @@ -374,6 +376,14 @@ int tegra_drm_submit(struct tegra_drm_context *context,
>  			goto fail;
>  		}
>
> +		offset = (u64)cmdbuf.offset + (u64)cmdbuf.words * sizeof(u32);
> +		obj = host1x_to_tegra_bo(bo);
> +
> +		if (offset & 3 || offset > obj->gem.size) {
> +			err = -EINVAL;
> +			goto fail;
> +		}
> +
>  		host1x_job_add_gather(job, bo, cmdbuf.words, cmdbuf.offset);
>  		num_cmdbufs--;
>  		cmdbufs++;
> @@ -381,11 +391,31 @@ int tegra_drm_submit(struct tegra_drm_context *context,
>
>  	/* copy and resolve relocations from submit */
>  	while (num_relocs--) {
> +		struct host1x_reloc *reloc;
> +		struct tegra_bo *obj;
> +
>  		err = host1x_reloc_copy_from_user(&job->relocarray[num_relocs],
>  						  &relocs[num_relocs], drm,
>  						  file);
>  		if (err < 0)
>  			goto fail;
> +
> +		reloc = &job->relocarray[num_relocs];
> +		obj = host1x_to_tegra_bo(reloc->cmdbuf.bo);
> +
> +		if (reloc->cmdbuf.offset & 3 ||
> +		    reloc->cmdbuf.offset > obj->gem.size) {

This could still fail if the bo's size is not divisible by 4, even with 
 >= comparison (we would overwrite the buffer by 1 to 3 bytes). I would 
do the same as in the gather case, i.e. find out the address immediately 
after the write and compare using >. Perhaps add a helper function if it 
makes sense. I also don't think the "& 3" checks are needed.

> +			err = -EINVAL;
> +			goto fail;
> +		}
> +
> +		obj = host1x_to_tegra_bo(reloc->target.bo);
> +
> +		if (reloc->target.offset & 3 ||
> +		    reloc->target.offset > obj->gem.size) {
> +			err = -EINVAL;
> +			goto fail;
> +		}
>  	}
>
>  	if (copy_from_user(job->waitchk, waitchks,
> diff --git a/drivers/gpu/drm/tegra/gem.c b/drivers/gpu/drm/tegra/gem.c
> index b76d7ac75696..a0ff30c01ac1 100644
> --- a/drivers/gpu/drm/tegra/gem.c
> +++ b/drivers/gpu/drm/tegra/gem.c
> @@ -20,11 +20,6 @@
>  #include "drm.h"
>  #include "gem.h"
>
> -static inline struct tegra_bo *host1x_to_tegra_bo(struct host1x_bo *bo)
> -{
> -	return container_of(bo, struct tegra_bo, base);
> -}
> -
>  static void tegra_bo_put(struct host1x_bo *bo)
>  {
>  	struct tegra_bo *obj = host1x_to_tegra_bo(bo);
> diff --git a/drivers/gpu/drm/tegra/gem.h b/drivers/gpu/drm/tegra/gem.h
> index 6c5f12ac0087..8b32a6fd586d 100644
> --- a/drivers/gpu/drm/tegra/gem.h
> +++ b/drivers/gpu/drm/tegra/gem.h
> @@ -52,6 +52,11 @@ static inline struct tegra_bo *to_tegra_bo(struct drm_gem_object *gem)
>  	return container_of(gem, struct tegra_bo, gem);
>  }
>
> +static inline struct tegra_bo *host1x_to_tegra_bo(struct host1x_bo *bo)
> +{
> +	return container_of(bo, struct tegra_bo, base);
> +}
> +
>  struct tegra_bo *tegra_bo_create(struct drm_device *drm, size_t size,
>  				 unsigned long flags);
>  struct tegra_bo *tegra_bo_create_with_handle(struct drm_file *file,
>