Re: [PATCH] scsi: 3w-sas: Replace 1-element arrays with flexible array members

["Gustavo A. R. Silva" <gustavoars@kernel.org>]

On Wed, Jan 04, 2023 at 04:48:01PM -0800, Kees Cook wrote:
> One-element arrays (and multi-element arrays being treated as
> dynamically sized) are deprecated[1] and are being replaced with
> flexible array members in support of the ongoing efforts to tighten the
> FORTIFY_SOURCE routines on memcpy(), correctly instrument array indexing
> with UBSAN_BOUNDS, and to globally enable -fstrict-flex-arrays=3.
> 
> Replace one-element arrays with flexible-array member in TW_Ioctl_Buf_Apache
> and TW_Param_Apache, adjusting the explicit sizing calculations at the
> same time.
> 
> This results in no differences in binary output.
> 
> [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#zero-length-and-one-element-arrays
> 
> Cc: Adam Radford <aradford@gmail.com>
> Cc: "James E.J. Bottomley" <jejb@linux.ibm.com>
> Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
> Cc: "Gustavo A. R. Silva" <gustavoars@kernel.org>
> Cc: linux-scsi@vger.kernel.org
> Signed-off-by: Kees Cook <keescook@chromium.org>

This is great. :) It's quite similar to this other commit:

	44c5027bb5c8 ("scsi: 3w-9xxx: Use flexible array members to avoid struct padding")

Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>

Thanks!
--
Gustavo

> ---
>  drivers/scsi/3w-sas.c | 12 ++++++------
>  drivers/scsi/3w-sas.h |  4 ++--
>  2 files changed, 8 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/scsi/3w-sas.c b/drivers/scsi/3w-sas.c
> index 3ebe66151dcb..f41c93454f0c 100644
> --- a/drivers/scsi/3w-sas.c
> +++ b/drivers/scsi/3w-sas.c
> @@ -690,7 +690,7 @@ static void twl_load_sgl(TW_Device_Extension *tw_dev, TW_Command_Full *full_comm
>  		newcommand->request_id__lunl =
>  			cpu_to_le16(TW_REQ_LUN_IN(TW_LUN_OUT(newcommand->request_id__lunl), request_id));
>  		if (length) {
> -			newcommand->sg_list[0].address = TW_CPU_TO_SGL(dma_handle + sizeof(TW_Ioctl_Buf_Apache) - 1);
> +			newcommand->sg_list[0].address = TW_CPU_TO_SGL(dma_handle + sizeof(TW_Ioctl_Buf_Apache));
>  			newcommand->sg_list[0].length = TW_CPU_TO_SGL(length);
>  		}
>  		newcommand->sgl_entries__lunh =
> @@ -702,7 +702,7 @@ static void twl_load_sgl(TW_Device_Extension *tw_dev, TW_Command_Full *full_comm
>  		if (TW_SGL_OUT(oldcommand->opcode__sgloffset)) {
>  			/* Load the sg list */
>  			sgl = (TW_SG_Entry_ISO *)((u32 *)oldcommand+oldcommand->size - (sizeof(TW_SG_Entry_ISO)/4) + pae + (sizeof(dma_addr_t) > 4 ? 1 : 0));
> -			sgl->address = TW_CPU_TO_SGL(dma_handle + sizeof(TW_Ioctl_Buf_Apache) - 1);
> +			sgl->address = TW_CPU_TO_SGL(dma_handle + sizeof(TW_Ioctl_Buf_Apache));
>  			sgl->length = TW_CPU_TO_SGL(length);
>  			oldcommand->size += pae;
>  			oldcommand->size += sizeof(dma_addr_t) > 4 ? 1 : 0;
> @@ -748,7 +748,7 @@ static long twl_chrdev_ioctl(struct file *file, unsigned int cmd, unsigned long
>  	data_buffer_length_adjusted = (driver_command.buffer_length + 511) & ~511;
>  
>  	/* Now allocate ioctl buf memory */
> -	cpu_addr = dma_alloc_coherent(&tw_dev->tw_pci_dev->dev, data_buffer_length_adjusted+sizeof(TW_Ioctl_Buf_Apache) - 1, &dma_handle, GFP_KERNEL);
> +	cpu_addr = dma_alloc_coherent(&tw_dev->tw_pci_dev->dev, data_buffer_length_adjusted + sizeof(TW_Ioctl_Buf_Apache), &dma_handle, GFP_KERNEL);
>  	if (!cpu_addr) {
>  		retval = -ENOMEM;
>  		goto out2;
> @@ -757,7 +757,7 @@ static long twl_chrdev_ioctl(struct file *file, unsigned int cmd, unsigned long
>  	tw_ioctl = (TW_Ioctl_Buf_Apache *)cpu_addr;
>  
>  	/* Now copy down the entire ioctl */
> -	if (copy_from_user(tw_ioctl, argp, driver_command.buffer_length + sizeof(TW_Ioctl_Buf_Apache) - 1))
> +	if (copy_from_user(tw_ioctl, argp, driver_command.buffer_length + sizeof(TW_Ioctl_Buf_Apache)))
>  		goto out3;
>  
>  	/* See which ioctl we are doing */
> @@ -815,11 +815,11 @@ static long twl_chrdev_ioctl(struct file *file, unsigned int cmd, unsigned long
>  	}
>  
>  	/* Now copy the entire response to userspace */
> -	if (copy_to_user(argp, tw_ioctl, sizeof(TW_Ioctl_Buf_Apache) + driver_command.buffer_length - 1) == 0)
> +	if (copy_to_user(argp, tw_ioctl, sizeof(TW_Ioctl_Buf_Apache) + driver_command.buffer_length) == 0)
>  		retval = 0;
>  out3:
>  	/* Now free ioctl buf memory */
> -	dma_free_coherent(&tw_dev->tw_pci_dev->dev, data_buffer_length_adjusted+sizeof(TW_Ioctl_Buf_Apache) - 1, cpu_addr, dma_handle);
> +	dma_free_coherent(&tw_dev->tw_pci_dev->dev, data_buffer_length_adjusted + sizeof(TW_Ioctl_Buf_Apache), cpu_addr, dma_handle);
>  out2:
>  	mutex_unlock(&tw_dev->ioctl_lock);
>  out:
> diff --git a/drivers/scsi/3w-sas.h b/drivers/scsi/3w-sas.h
> index b0508039a280..096dec29e2ac 100644
> --- a/drivers/scsi/3w-sas.h
> +++ b/drivers/scsi/3w-sas.h
> @@ -335,7 +335,7 @@ typedef struct TAG_TW_Ioctl_Apache {
>  	TW_Ioctl_Driver_Command driver_command;
>  	char padding[488];
>  	TW_Command_Full firmware_command;
> -	char data_buffer[1];
> +	char data_buffer[];
>  } TW_Ioctl_Buf_Apache;
>  
>  /* GetParam descriptor */
> @@ -344,7 +344,7 @@ typedef struct {
>  	unsigned short	parameter_id;
>  	unsigned short	parameter_size_bytes;
>  	unsigned short  actual_parameter_size_bytes;
> -	unsigned char	data[1];
> +	unsigned char	data[];
>  } TW_Param_Apache;
>  
>  /* Compatibility information structure */
> -- 
> 2.34.1
>