re: libnvdimm: remove else after return in nsio_rw_bytes()

re: libnvdimm: remove else after return in nsio_rw_bytes()

[Colin Ian King]

Hi there,

While performing some bi-weekly static analysis on linux-next I
discovered a potential -ve sized memcpy in drivers/nvdimm/claim.c in
nsio_rw_bytes() which probably some attention.

CoverityScan found this issue, I think it stems from commit
d37806dc37b42b05515849b0444f09f493cb4cba ("libnvdimm: remove else after
return in nsio_rw_bytes()").

This issue occurs when nvdimm_clear_poison can return a -ve error such
as -ENXIO as follows:

	cleared = nvdimm_clear_poison(&ndns->dev, offset, size);
	if (cleared != size) {
		size = cleared;
		rc = -EIO;
	}

a little later a memcpy_to_pmem() occurs using the -ve size:

	memcpy_to_pmem(nsio->addr + offset, buf, size);

..which doesn't look sane to me.  I'm not sure what the default behavior
should be for this kind of error handling, so I'm drawing this issue to
your attention.

Colin
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