linux-kernel - [212/244] pci: Dont crash when reading mpss from root complex

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Date:	Wed, 28 Sep 2011 15:02:56 -0700
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Jon Mason <mason@...i.com>
Subject: [212/244] pci: Dont crash when reading mpss from root complex

3.0-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Benjamin Herrenschmidt <benh@...nel.crashing.org>

commit 1a4b1a41b8a3d5256019854e851beed063b34344 upstream.

In pcie_find_smpss(), we have the following statement:

 	if (dev->is_hotplug_bridge && (!list_is_singular(&dev->bus->devices) ||
	    dev->bus->self->pcie_type != PCI_EXP_TYPE_ROOT_PORT))

The problem is that at least on my machine, this gets called for the
root complex (virtual P2P bridge), and dev->bus->self is NULL since
the parent bus for this is not itself anchor to a PCI device.

This adds the necessary NULL check.

Signed-off-by: Benjamin Herrenschmidt <benh@...nel.crashing.org>
Acked-by: Jon Mason <mason@...i.com>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 drivers/pci/probe.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -1352,7 +1352,8 @@ static int pcie_find_smpss(struct pci_de
 	 * will occur as normal.
 	 */
 	if (dev->is_hotplug_bridge && (!list_is_singular(&dev->bus->devices) ||
-	    dev->bus->self->pcie_type != PCI_EXP_TYPE_ROOT_PORT))
+	     (dev->bus->self &&
+	      dev->bus->self->pcie_type != PCI_EXP_TYPE_ROOT_PORT)))
 		*smpss = 0;
 
 	if (*smpss > dev->pcie_mpss)


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