Re: [PATCH v4] media: mtk-vpu: avoid unaligned access to DTCM buffer.

[Hans Verkuil]

On 02/03/2020 05:40, Hsin-Yi Wang wrote:
> media: mtk-vpu: avoid unaligned access to DTCM buffer.
> 
> Previously, vpu->recv_buf and send_buf are forced cast from
> void __iomem *tcm. vpu->recv_buf->share_buf is passed to
> vpu_ipi_desc.handler(). It's not able to do unaligned access. Otherwise
> kernel would crash due to unable to handle kernel paging request.
> 
> struct vpu_run {
> 	u32 signaled;
> 	char fw_ver[VPU_FW_VER_LEN];
> 	unsigned int	dec_capability;
> 	unsigned int	enc_capability;
> 	wait_queue_head_t wq;
> };
> 
> fw_ver starts at 4 byte boundary. If system enables
> CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS, strscpy() will do
> read_word_at_a_time(), which tries to read 8-byte: *(unsigned long *)addr
> 
> vpu_init_ipi_handler() calls strscpy(), which would lead to crash.
> 
> vpu_init_ipi_handler() and several other handlers (eg.
> vpu_dec_ipi_handler) only do read access to this data, so they can be
> const, and we can use memcpy_fromio() to copy the buf to another non iomem
> buffer then pass to handler.
> 
> Fixes: 85709cbf1524 ("media: replace strncpy() by strscpy()")
> Signed-off-by: Hsin-Yi Wang <hsinyi@xxxxxxxxxxxx>
> ---
> Change in v4:
> - Remove forced casting recv_buf from tcm. Copy iomem data before passing
>   to handler.
> Change in v2, v3:
> - fix sparse warnings.
> ---
>  drivers/media/platform/mtk-mdp/mtk_mdp_vpu.c  |  9 ++--
>  .../media/platform/mtk-vcodec/vdec_vpu_if.c   |  6 +--
>  .../media/platform/mtk-vcodec/venc_vpu_if.c   | 12 ++---
>  drivers/media/platform/mtk-vpu/mtk_vpu.c      | 45 ++++++++++---------
>  drivers/media/platform/mtk-vpu/mtk_vpu.h      |  2 +-
>  5 files changed, 38 insertions(+), 36 deletions(-)
> 
> diff --git a/drivers/media/platform/mtk-mdp/mtk_mdp_vpu.c b/drivers/media/platform/mtk-mdp/mtk_mdp_vpu.c
> index 6720d11f50cf..dc95b8a44759 100644
> --- a/drivers/media/platform/mtk-mdp/mtk_mdp_vpu.c
> +++ b/drivers/media/platform/mtk-mdp/mtk_mdp_vpu.c
> @@ -15,7 +15,7 @@ static inline struct mtk_mdp_ctx *vpu_to_ctx(struct mtk_mdp_vpu *vpu)
>  	return container_of(vpu, struct mtk_mdp_ctx, vpu);
>  }
>  
> -static void mtk_mdp_vpu_handle_init_ack(struct mdp_ipi_comm_ack *msg)
> +static void mtk_mdp_vpu_handle_init_ack(const struct mdp_ipi_comm_ack *msg)
>  {
>  	struct mtk_mdp_vpu *vpu = (struct mtk_mdp_vpu *)
>  					(unsigned long)msg->ap_inst;
> @@ -26,10 +26,11 @@ static void mtk_mdp_vpu_handle_init_ack(struct mdp_ipi_comm_ack *msg)
>  	vpu->inst_addr = msg->vpu_inst_addr;
>  }
>  
> -static void mtk_mdp_vpu_ipi_handler(void *data, unsigned int len, void *priv)
> +static void mtk_mdp_vpu_ipi_handler(const void *data, unsigned int len,
> +				    void *priv)
>  {
> -	unsigned int msg_id = *(unsigned int *)data;
> -	struct mdp_ipi_comm_ack *msg = (struct mdp_ipi_comm_ack *)data;
> +	unsigned int msg_id = *(const unsigned int *)data;
> +	const struct mdp_ipi_comm_ack *msg = data;

Why not just do:

	const struct mdp_ipi_comm_ack *msg = data;
	unsigned int msg_id = msg->msg_id;

Much cleaner.

Other than this small issue this patch looks nice. No more sparse/smatch warnings
and no more weird casts :-)

Regards,

	Hans

>  	struct mtk_mdp_vpu *vpu = (struct mtk_mdp_vpu *)
>  					(unsigned long)msg->ap_inst;
>  	struct mtk_mdp_ctx *ctx;
> diff --git a/drivers/media/platform/mtk-vcodec/vdec_vpu_if.c b/drivers/media/platform/mtk-vcodec/vdec_vpu_if.c
> index 70abfd4cd4b9..948a12fd9d46 100644
> --- a/drivers/media/platform/mtk-vcodec/vdec_vpu_if.c
> +++ b/drivers/media/platform/mtk-vcodec/vdec_vpu_if.c
> @@ -9,7 +9,7 @@
>  #include "vdec_ipi_msg.h"
>  #include "vdec_vpu_if.h"
>  
> -static void handle_init_ack_msg(struct vdec_vpu_ipi_init_ack *msg)
> +static void handle_init_ack_msg(const struct vdec_vpu_ipi_init_ack *msg)
>  {
>  	struct vdec_vpu_inst *vpu = (struct vdec_vpu_inst *)
>  					(unsigned long)msg->ap_inst_addr;
> @@ -34,9 +34,9 @@ static void handle_init_ack_msg(struct vdec_vpu_ipi_init_ack *msg)
>   * This function runs in interrupt context and it means there's an IPI MSG
>   * from VPU.
>   */
> -static void vpu_dec_ipi_handler(void *data, unsigned int len, void *priv)
> +static void vpu_dec_ipi_handler(const void *data, unsigned int len, void *priv)
>  {
> -	struct vdec_vpu_ipi_ack *msg = data;
> +	const struct vdec_vpu_ipi_ack *msg = data;
>  	struct vdec_vpu_inst *vpu = (struct vdec_vpu_inst *)
>  					(unsigned long)msg->ap_inst_addr;
>  
> diff --git a/drivers/media/platform/mtk-vcodec/venc_vpu_if.c b/drivers/media/platform/mtk-vcodec/venc_vpu_if.c
> index 3e931b0ed096..9540709c1905 100644
> --- a/drivers/media/platform/mtk-vcodec/venc_vpu_if.c
> +++ b/drivers/media/platform/mtk-vcodec/venc_vpu_if.c
> @@ -8,26 +8,26 @@
>  #include "venc_ipi_msg.h"
>  #include "venc_vpu_if.h"
>  
> -static void handle_enc_init_msg(struct venc_vpu_inst *vpu, void *data)
> +static void handle_enc_init_msg(struct venc_vpu_inst *vpu, const void *data)
>  {
> -	struct venc_vpu_ipi_msg_init *msg = data;
> +	const struct venc_vpu_ipi_msg_init *msg = data;
>  
>  	vpu->inst_addr = msg->vpu_inst_addr;
>  	vpu->vsi = vpu_mapping_dm_addr(vpu->dev, msg->vpu_inst_addr);
>  }
>  
> -static void handle_enc_encode_msg(struct venc_vpu_inst *vpu, void *data)
> +static void handle_enc_encode_msg(struct venc_vpu_inst *vpu, const void *data)
>  {
> -	struct venc_vpu_ipi_msg_enc *msg = data;
> +	const struct venc_vpu_ipi_msg_enc *msg = data;
>  
>  	vpu->state = msg->state;
>  	vpu->bs_size = msg->bs_size;
>  	vpu->is_key_frm = msg->is_key_frm;
>  }
>  
> -static void vpu_enc_ipi_handler(void *data, unsigned int len, void *priv)
> +static void vpu_enc_ipi_handler(const void *data, unsigned int len, void *priv)
>  {
> -	struct venc_vpu_ipi_msg_common *msg = data;
> +	const struct venc_vpu_ipi_msg_common *msg = data;
>  	struct venc_vpu_inst *vpu =
>  		(struct venc_vpu_inst *)(unsigned long)msg->venc_inst;
>  
> diff --git a/drivers/media/platform/mtk-vpu/mtk_vpu.c b/drivers/media/platform/mtk-vpu/mtk_vpu.c
> index a768707abb94..2fbccc9b247b 100644
> --- a/drivers/media/platform/mtk-vpu/mtk_vpu.c
> +++ b/drivers/media/platform/mtk-vpu/mtk_vpu.c
> @@ -203,8 +203,8 @@ struct mtk_vpu {
>  	struct vpu_run run;
>  	struct vpu_wdt wdt;
>  	struct vpu_ipi_desc ipi_desc[IPI_MAX];
> -	struct share_obj *recv_buf;
> -	struct share_obj *send_buf;
> +	struct share_obj __iomem *recv_buf;
> +	struct share_obj __iomem *send_buf;
>  	struct device *dev;
>  	struct clk *clk;
>  	bool fw_loaded;
> @@ -292,7 +292,7 @@ int vpu_ipi_send(struct platform_device *pdev,
>  		 unsigned int len)
>  {
>  	struct mtk_vpu *vpu = platform_get_drvdata(pdev);
> -	struct share_obj *send_obj = vpu->send_buf;
> +	struct share_obj __iomem *send_obj = vpu->send_buf;
>  	unsigned long timeout;
>  	int ret = 0;
>  
> @@ -325,9 +325,9 @@ int vpu_ipi_send(struct platform_device *pdev,
>  		}
>  	} while (vpu_cfg_readl(vpu, HOST_TO_VPU));
>  
> -	memcpy((void *)send_obj->share_buf, buf, len);
> -	send_obj->len = len;
> -	send_obj->id = id;
> +	memcpy_toio(send_obj->share_buf, buf, len);
> +	writel(len, &send_obj->len);
> +	writel(id, &send_obj->id);
>  
>  	vpu->ipi_id_ack[id] = false;
>  	/* send the command to VPU */
> @@ -600,10 +600,10 @@ int vpu_load_firmware(struct platform_device *pdev)
>  }
>  EXPORT_SYMBOL_GPL(vpu_load_firmware);
>  
> -static void vpu_init_ipi_handler(void *data, unsigned int len, void *priv)
> +static void vpu_init_ipi_handler(const void *data, unsigned int len, void *priv)
>  {
> -	struct mtk_vpu *vpu = (struct mtk_vpu *)priv;
> -	struct vpu_run *run = (struct vpu_run *)data;
> +	struct mtk_vpu *vpu = priv;
> +	const struct vpu_run *run = data;
>  
>  	vpu->run.signaled = run->signaled;
>  	strscpy(vpu->run.fw_ver, run->fw_ver, sizeof(vpu->run.fw_ver));
> @@ -700,19 +700,21 @@ static int vpu_alloc_ext_mem(struct mtk_vpu *vpu, u32 fw_type)
>  
>  static void vpu_ipi_handler(struct mtk_vpu *vpu)
>  {
> -	struct share_obj *rcv_obj = vpu->recv_buf;
> +	struct share_obj __iomem *rcv_obj = vpu->recv_buf;
>  	struct vpu_ipi_desc *ipi_desc = vpu->ipi_desc;
> -
> -	if (rcv_obj->id < IPI_MAX && ipi_desc[rcv_obj->id].handler) {
> -		ipi_desc[rcv_obj->id].handler(rcv_obj->share_buf,
> -					      rcv_obj->len,
> -					      ipi_desc[rcv_obj->id].priv);
> -		if (rcv_obj->id > IPI_VPU_INIT) {
> -			vpu->ipi_id_ack[rcv_obj->id] = true;
> +	unsigned char data[SHARE_BUF_SIZE];
> +	s32 id = readl(&rcv_obj->id);
> +
> +	memcpy_fromio(data, rcv_obj->share_buf, sizeof(data));
> +	if (id < IPI_MAX && ipi_desc[id].handler) {
> +		ipi_desc[id].handler(data, readl(&rcv_obj->len),
> +				     ipi_desc[id].priv);
> +		if (id > IPI_VPU_INIT) {
> +			vpu->ipi_id_ack[id] = true;
>  			wake_up(&vpu->ack_wq);
>  		}
>  	} else {
> -		dev_err(vpu->dev, "No such ipi id = %d\n", rcv_obj->id);
> +		dev_err(vpu->dev, "No such ipi id = %d\n", id);
>  	}
>  }
>  
> @@ -722,11 +724,10 @@ static int vpu_ipi_init(struct mtk_vpu *vpu)
>  	vpu_cfg_writel(vpu, 0x0, VPU_TO_HOST);
>  
>  	/* shared buffer initialization */
> -	vpu->recv_buf = (__force struct share_obj *)(vpu->reg.tcm +
> -						     VPU_DTCM_OFFSET);
> +	vpu->recv_buf = vpu->reg.tcm + VPU_DTCM_OFFSET;
>  	vpu->send_buf = vpu->recv_buf + 1;
> -	memset(vpu->recv_buf, 0, sizeof(struct share_obj));
> -	memset(vpu->send_buf, 0, sizeof(struct share_obj));
> +	memset_io(vpu->recv_buf, 0, sizeof(struct share_obj));
> +	memset_io(vpu->send_buf, 0, sizeof(struct share_obj));
>  
>  	return 0;
>  }
> diff --git a/drivers/media/platform/mtk-vpu/mtk_vpu.h b/drivers/media/platform/mtk-vpu/mtk_vpu.h
> index d4453b4bcee9..ee7c552ce928 100644
> --- a/drivers/media/platform/mtk-vpu/mtk_vpu.h
> +++ b/drivers/media/platform/mtk-vpu/mtk_vpu.h
> @@ -15,7 +15,7 @@
>   * VPU interfaces with other blocks by share memory and interrupt.
>   **/
>  
> -typedef void (*ipi_handler_t) (void *data,
> +typedef void (*ipi_handler_t) (const void *data,
>  			       unsigned int len,
>  			       void *priv);
>  
>