Re: [PATCH v3][next] scsi: aacraid: Replace one-element array with flexible-array member

[Gustavo A. R. Silva]

Hi Martin,

Friendly ping: could you take this patch, please? :)

Thanks!
--
Gustavo

On 4/21/21 13:56, Gustavo A. R. Silva wrote:
> There is a regular need in the kernel to provide a way to declare having
> a dynamically sized set of trailing elements in a structure. Kernel code
> should always use “flexible array members”[1] for these cases. The older
> style of one-element or zero-length arrays should no longer be used[2].
> 
> Refactor the code according to the use of a flexible-array member in
> struct aac_raw_io2 instead of one-element array, and use the
> struct_size() helper.
> 
> Also, this helps with the ongoing efforts to enable -Warray-bounds by
> fixing the following warnings:
> 
> drivers/scsi/aacraid/aachba.c: In function ‘aac_build_sgraw2’:
> drivers/scsi/aacraid/aachba.c:3970:18: warning: array subscript 1 is above array bounds of ‘struct sge_ieee1212[1]’ [-Warray-bounds]
>  3970 |     if (rio2->sge[j].length % (i*PAGE_SIZE)) {
>       |         ~~~~~~~~~^~~
> drivers/scsi/aacraid/aachba.c:3974:27: warning: array subscript 1 is above array bounds of ‘struct sge_ieee1212[1]’ [-Warray-bounds]
>  3974 |     nseg_new += (rio2->sge[j].length / (i*PAGE_SIZE));
>       |                  ~~~~~~~~~^~~
> drivers/scsi/aacraid/aachba.c:4011:28: warning: array subscript 1 is above array bounds of ‘struct sge_ieee1212[1]’ [-Warray-bounds]
>  4011 |   for (j = 0; j < rio2->sge[i].length / (pages * PAGE_SIZE); ++j) {
>       |                   ~~~~~~~~~^~~
> drivers/scsi/aacraid/aachba.c:4012:24: warning: array subscript 1 is above array bounds of ‘struct sge_ieee1212[1]’ [-Warray-bounds]
>  4012 |    addr_low = rio2->sge[i].addrLow + j * pages * PAGE_SIZE;
>       |               ~~~~~~~~~^~~
> drivers/scsi/aacraid/aachba.c:4014:33: warning: array subscript 1 is above array bounds of ‘struct sge_ieee1212[1]’ [-Warray-bounds]
>  4014 |    sge[pos].addrHigh = rio2->sge[i].addrHigh;
>       |                        ~~~~~~~~~^~~
> drivers/scsi/aacraid/aachba.c:4015:28: warning: array subscript 1 is above array bounds of ‘struct sge_ieee1212[1]’ [-Warray-bounds]
>  4015 |    if (addr_low < rio2->sge[i].addrLow)
>       |                   ~~~~~~~~~^~~
> 
> [1] https://en.wikipedia.org/wiki/Flexible_array_member
> [2] https://www.kernel.org/doc/html/v5.9/process/deprecated.html#zero-length-and-one-element-arrays
> 
> Link: https://github.com/KSPP/linux/issues/79
> Link: https://github.com/KSPP/linux/issues/109
> Build-tested-by: kernel test robot <lkp@xxxxxxxxx>
> Link: https://lore.kernel.org/lkml/60414244.ur4%2FkI+fBF1ohKZs%25lkp@xxxxxxxxx/
> Signed-off-by: Gustavo A. R. Silva <gustavoars@xxxxxxxxxx>
> ---
> Changes in v3:
>  - Use (nseg_new-1)*sizeof(struct sge_ieee1212) to calculate
>    size in call to memcpy() in order to avoid any confusion.
> 
> Changes in v2:
>  - Add code comment for clarification.
> 
>  drivers/scsi/aacraid/aachba.c  | 10 +++++-----
>  drivers/scsi/aacraid/aacraid.h |  2 +-
>  2 files changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/scsi/aacraid/aachba.c b/drivers/scsi/aacraid/aachba.c
> index f1f62b5da8b7..46b8dffce2dd 100644
> --- a/drivers/scsi/aacraid/aachba.c
> +++ b/drivers/scsi/aacraid/aachba.c
> @@ -1235,8 +1235,8 @@ static int aac_read_raw_io(struct fib * fib, struct scsi_cmnd * cmd, u64 lba, u3
>  		if (ret < 0)
>  			return ret;
>  		command = ContainerRawIo2;
> -		fibsize = sizeof(struct aac_raw_io2) +
> -			((le32_to_cpu(readcmd2->sgeCnt)-1) * sizeof(struct sge_ieee1212));
> +		fibsize = struct_size(readcmd2, sge,
> +				     le32_to_cpu(readcmd2->sgeCnt));
>  	} else {
>  		struct aac_raw_io *readcmd;
>  		readcmd = (struct aac_raw_io *) fib_data(fib);
> @@ -1366,8 +1366,8 @@ static int aac_write_raw_io(struct fib * fib, struct scsi_cmnd * cmd, u64 lba, u
>  		if (ret < 0)
>  			return ret;
>  		command = ContainerRawIo2;
> -		fibsize = sizeof(struct aac_raw_io2) +
> -			((le32_to_cpu(writecmd2->sgeCnt)-1) * sizeof(struct sge_ieee1212));
> +		fibsize = struct_size(writecmd2, sge,
> +				      le32_to_cpu(writecmd2->sgeCnt));
>  	} else {
>  		struct aac_raw_io *writecmd;
>  		writecmd = (struct aac_raw_io *) fib_data(fib);
> @@ -3998,7 +3998,7 @@ static int aac_convert_sgraw2(struct aac_raw_io2 *rio2, int pages, int nseg, int
>  	if (aac_convert_sgl == 0)
>  		return 0;
>  
> -	sge = kmalloc_array(nseg_new, sizeof(struct sge_ieee1212), GFP_ATOMIC);
> +	sge = kmalloc_array(nseg_new, sizeof(*sge), GFP_ATOMIC);
>  	if (sge == NULL)
>  		return -ENOMEM;
>  
> diff --git a/drivers/scsi/aacraid/aacraid.h b/drivers/scsi/aacraid/aacraid.h
> index e3e4ecbea726..3733df77bc65 100644
> --- a/drivers/scsi/aacraid/aacraid.h
> +++ b/drivers/scsi/aacraid/aacraid.h
> @@ -1929,7 +1929,7 @@ struct aac_raw_io2 {
>  	u8		bpComplete;	/* reserved for F/W use */
>  	u8		sgeFirstIndex;	/* reserved for F/W use */
>  	u8		unused[4];
> -	struct sge_ieee1212	sge[1];
> +	struct sge_ieee1212	sge[];
>  };
>  
>  #define CT_FLUSH_CACHE 129
>