[ 055/147] usb: host: xhci: Fix Null pointer dereferencing with 71c731a fornon-x86 systems

[Ben Hutchings]

3.2-stable review patch.  If anyone has any objections, please let me know.

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

From: Vivek Gautam <gautam.vivek@xxxxxxxxxxx>

commit 457a73d346187c2cc5d599072f38676f18f130e0 upstream.

In 71c731a: usb: host: xhci: Fix Compliance Mode on SN65LVPE502CP Hardware
when extracting DMI strings (vendor or product_name) to mark them as quirk
we may get NULL pointer in case of non-x86 systems which won't define
CONFIG_DMI. Hence susbsequent strstr() calls crash while driver probing.

So, returning 'false' here in case we get a NULL vendor or product_name.

This is tested with ARM (exynos) system.

This patch should be backported to stable kernels as old as 3.6, that
contain the commit 71c731a296f1b08a3724bd1b514b64f1bda87a23 "usb: host:
xhci: Fix Compliance Mode on SN65LVPE502CP Hardware"

Signed-off-by: Vivek Gautam <gautam.vivek@xxxxxxxxxxx>
Signed-off-by: Sarah Sharp <sarah.a.sharp@xxxxxxxxxxxxxxx>
Reported-by: Sebastian Gottschall (DD-WRT) <s.gottschall@xxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 drivers/usb/host/xhci.c |    2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
index 52b04b0..8d7fcbb 100644
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -471,6 +471,8 @@ static bool compliance_mode_recovery_timer_quirk_check(void)
 
 	dmi_product_name = dmi_get_system_info(DMI_PRODUCT_NAME);
 	dmi_sys_vendor = dmi_get_system_info(DMI_SYS_VENDOR);
+	if (!dmi_product_name || !dmi_sys_vendor)
+		return false;
 
 	if (!(strstr(dmi_sys_vendor, "Hewlett-Packard")))
 		return false;


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