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

Gustavo A. R. Silva
2021-05-04T00:40:35Z

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@intel.com>
> Link: https://lore.kernel.org/lkml/60414244.ur4%2FkI+fBF1ohKZs%25lkp@intel.com/
> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
> ---
> 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
>