libnvdimm: fix mishandled nvdimm_clear_poison() return value

Colin, via static analysis, reports that the length could be negative
from nvdimm_clear_poison() in the error case. There was a similar
problem with commit 0a3f27b9a6a8 "libnvdimm, namespace: avoid multiple
sector calculations" that I noticed when merging the for-4.10/libnvdimm
topic branch into libnvdimm-for-next, but I missed this one. Fix both of
them to the following procedure:

* if we clear a block's worth of media, clear that many blocks in
  badblocks

* if we clear less than the requested size of the transfer return an
  error

* always invalidate cache after any non-error / non-zero
  nvdimm_clear_poison result

Fixes: 82bf1037f2ca ("libnvdimm: check and clear poison before writing to pmem")
Fixes: 0a3f27b9a6a8 ("libnvdimm, namespace: avoid multiple sector calculations")
Cc: Fabian Frederick <fabf@skynet.be>
Cc: Dave Jiang <dave.jiang@intel.com>
Reported-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

2 files changed, 19 insertions, 11 deletions

diff --git a/drivers/nvdimm/claim.c b/drivers/nvdimm/claim.c
index 97d1772774a8..b3323c0697f6 100644
--- a/drivers/nvdimm/claim.c
+++ b/drivers/nvdimm/claim.c
@@ -247,12 +247,13 @@ static int nsio_rw_bytes(struct nd_namespace_common *ndns,
                         long cleared;
 
                         cleared = nvdimm_clear_poison(&ndns->dev, offset, size);
-                        if (cleared != size) {
-                                size = cleared;
+                        if (cleared < size)
                                 rc = -EIO;
+                        if (cleared > 0 && cleared / 512) {
+                                cleared /= 512;
+                                badblocks_clear(&nsio->bb, sector, cleared);
                         }
-
-                        badblocks_clear(&nsio->bb, sector, cleared >> 9);
+                        invalidate_pmem(nsio->addr + offset, size);
                 } else
                         rc = -EIO;
         }
diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index bcc359a4e64d..ecf79fd64517 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -47,22 +47,29 @@ static struct nd_region *to_region(struct pmem_device *pmem)
         return to_nd_region(to_dev(pmem)->parent);
 }
 
-static void pmem_clear_poison(struct pmem_device *pmem, phys_addr_t offset,
+static int pmem_clear_poison(struct pmem_device *pmem, phys_addr_t offset,
                 unsigned int len)
 {
         struct device *dev = to_dev(pmem);
-        sector_t sector, cleared;
+        sector_t sector;
+        long cleared;
+        int rc = 0;
 
         sector = (offset - pmem->data_offset) / 512;
-        cleared = nvdimm_clear_poison(dev, pmem->phys_addr + offset, len) / 512;
 
-        if (cleared) {
-                dev_dbg(dev, "%s: %#llx clear %ld sector%s\n",
-                                __func__, (unsigned long long) sector,
-                                cleared, cleared > 1 ? "s" : "");
+        cleared = nvdimm_clear_poison(dev, pmem->phys_addr + offset, len);
+        if (cleared < len)
+                rc = -EIO;
+        if (cleared > 0 && cleared / 512) {
+                cleared /= 512;
+                dev_dbg(dev, "%s: %#llx clear %ld sector%s\n", __func__,
+                                (unsigned long long) sector, cleared,
+                                cleared > 1 ? "s" : "");
                 badblocks_clear(&pmem->bb, sector, cleared);
         }
         invalidate_pmem(pmem->virt_addr + offset, len);
+
+        return rc;
 }
 
 static void write_pmem(void *pmem_addr, struct page *page,