Re: target: Add support for EXTENDED_COPY copy offload emulation

From: Dave Jones
Date: Fri Sep 13 2013 - 16:44:12 EST


On Fri, Sep 13, 2013 at 12:01:21AM +0000, Linux Kernel wrote:
> Gitweb: http://git.kernel.org/linus/;a=commit;h=cbf031f425fd0b30ff10ba83b612753189a6bbbf
> Commit: cbf031f425fd0b30ff10ba83b612753189a6bbbf
> Parent: 89c12cc925a7d0982dc53b743a42108acc76aef4
> Author: Nicholas Bellinger <nab@xxxxxxxxxxxxx>
> AuthorDate: Tue Aug 20 15:38:55 2013 -0700
> Committer: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>
> CommitDate: Tue Sep 10 16:48:43 2013 -0700
>
> target: Add support for EXTENDED_COPY copy offload emulation

...

> +static int target_xcopy_parse_segdesc_02(struct se_cmd *se_cmd, struct xcopy_op *xop,
> + unsigned char *p)
> +{
> + unsigned char *desc = p;
> + int dc = (desc[1] & 0x02);
> + unsigned short desc_len;
> +
> + desc_len = get_unaligned_be16(&desc[2]);
> + if (desc_len != 0x18) {
> + pr_err("XCOPY segment desc 0x02: Illegal desc_len:"
> + " %hu\n", desc_len);
> + return -EINVAL;
> + }
> +
> + xop->stdi = get_unaligned_be16(&desc[4]);
> + xop->dtdi = get_unaligned_be16(&desc[6]);
> + pr_debug("XCOPY seg desc 0x02: desc_len: %hu stdi: %hu dtdi: %hu, DC: %d\n",
> + desc_len, xop->stdi, xop->dtdi, dc);
> +
> + xop->nolb = get_unaligned_be16(&desc[10]);
> + xop->src_lba = get_unaligned_be64(&desc[12]);
> + xop->dst_lba = get_unaligned_be64(&desc[20]);
> + pr_debug("XCOPY seg desc 0x02: nolb: %hu src_lba: %llu dst_lba: %llu\n",
> + xop->nolb, (unsigned long long)xop->src_lba,
> + (unsigned long long)xop->dst_lba);
> +
> + if (dc != 0) {
> + xop->dbl = (desc[29] << 16) & 0xff;
> + xop->dbl |= (desc[30] << 8) & 0xff;
> + xop->dbl |= desc[31] & 0xff;
> +
> + pr_debug("XCOPY seg desc 0x02: DC=1 w/ dbl: %u\n", xop->dbl);
> + }
> + return 0;
> +}

Coverity picked up a new warning in this code.
It notes that (desc[30] << 8) & 0xff is always zero.

Did you want

xop->dbl = (desc[29] >> 16) & 0xff;

instead maybe ?

The << 16 looks suspect too, though it didn't warn on that.

Dave


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