Patch "device-dax: check devm_nsio_enable() return value" has been added to the 4.8-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    device-dax: check devm_nsio_enable() return value

to the 4.8-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     device-dax-check-devm_nsio_enable-return-value.patch
and it can be found in the queue-4.8 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 6a84fb4b4e439a8ef0ce19ec7e7661ad76f655c9 Mon Sep 17 00:00:00 2001
From: Dan Williams <dan.j.williams@intel.com>
Date: Fri, 28 Oct 2016 14:34:51 -0700
Subject: device-dax: check devm_nsio_enable() return value

From: Dan Williams <dan.j.williams@intel.com>

commit 6a84fb4b4e439a8ef0ce19ec7e7661ad76f655c9 upstream.

If the dax_pmem driver is passed a resource that is already busy the
driver probe attempt should fail with a message like the following:

  dax_pmem dax0.1: could not reserve region [mem 0x100000000-0x11fffffff]

However, if we do not catch the error we crash for the obvious reason of
accessing memory that is not mapped.

 BUG: unable to handle kernel paging request at ffffc90020001000
 IP: [<ffffffff81496712>] __memcpy+0x12/0x20
 [..]
 Call Trace:
  [<ffffffff815c4960>] ? nsio_rw_bytes+0x60/0x180
  [<ffffffff815c6045>] nd_pfn_validate+0x75/0x320
  [<ffffffff815c63a9>] nvdimm_setup_pfn+0xb9/0x5d0
  [<ffffffff815c48ef>] ? devm_nsio_enable+0xff/0x110
  [<ffffffff815cb699>] dax_pmem_probe+0x59/0x260

Fixes: ab68f2622136 ("/dev/dax, pmem: direct access to persistent memory")
Reported-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/dax/pmem.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/drivers/dax/pmem.c
+++ b/drivers/dax/pmem.c
@@ -77,7 +77,9 @@ static int dax_pmem_probe(struct device
 	nsio = to_nd_namespace_io(&ndns->dev);
 
 	/* parse the 'pfn' info block via ->rw_bytes */
-	devm_nsio_enable(dev, nsio);
+	rc = devm_nsio_enable(dev, nsio);
+	if (rc)
+		return rc;
 	altmap = nvdimm_setup_pfn(nd_pfn, &res, &__altmap);
 	if (IS_ERR(altmap))
 		return PTR_ERR(altmap);


Patches currently in stable-queue which might be from dan.j.williams@intel.com are

queue-4.8/device-dax-fail-all-private-mapping-attempts.patch
queue-4.8/device-dax-check-devm_nsio_enable-return-value.patch