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Subject[PATCH] Fix stack corruption on some architectures
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Date
There is no need to get an interface specification if we know it's the
wrong one; trivial change. The big thing, though, was explained in the
#mipslinux IRC channel:
[Mon 2013-08-19 12:28:21 PM PDT] <headless> guys, are you sure it's not "DMA off stack" case?
[Mon 2013-08-19 12:28:35 PM PDT] <headless> it's a known stack corruptor on non-coherent arches
[Mon 2013-08-19 12:31:48 PM PDT] <DonkeyHotei> headless: for usb/ehci?
[Mon 2013-08-19 12:34:11 PM PDT] <DonkeyHotei> headless: explain
[Mon 2013-08-19 12:35:38 PM PDT] <headless> usb_control_msg() (or other such func) should not use buffer on stack. DMA from/to stack is prohibited
[Mon 2013-08-19 12:35:58 PM PDT] <headless> and EHCI uses DMA on control xfers (as well as all the others)

Signed-off-by: Daniel Gimpelevich <daniel@gimpelevich.san-francisco.ca.us>
---
drivers/net/usb/hso.c | 15 ++++++++++-----
1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/drivers/net/usb/hso.c b/drivers/net/usb/hso.c
index cba1d46..86292e6 100644
--- a/drivers/net/usb/hso.c
+++ b/drivers/net/usb/hso.c
@@ -2816,13 +2816,16 @@ exit:
static int hso_get_config_data(struct usb_interface *interface)
{
struct usb_device *usbdev = interface_to_usbdev(interface);
- u8 config_data[17];
+ u8 *config_data = kmalloc(17, GFP_KERNEL);
u32 if_num = interface->altsetting->desc.bInterfaceNumber;
s32 result;

+ if (!config_data)
+ return -ENOMEM;
if (usb_control_msg(usbdev, usb_rcvctrlpipe(usbdev, 0),
0x86, 0xC0, 0, 0, config_data, 17,
USB_CTRL_SET_TIMEOUT) != 0x11) {
+ kfree(config_data);
return -EIO;
}

@@ -2873,6 +2876,7 @@ static int hso_get_config_data(struct usb_interface *interface)
if (config_data[16] & 0x1)
result |= HSO_INFO_CRC_BUG;

+ kfree(config_data);
return result;
}

@@ -2886,6 +2890,11 @@ static int hso_probe(struct usb_interface *interface,
struct hso_shared_int *shared_int;
struct hso_device *tmp_dev = NULL;

+ if (interface->cur_altsetting->desc.bInterfaceClass != 0xFF) {
+ dev_err(&interface->dev, "Not our interface\n");
+ return -ENODEV;
+ }
+
if_num = interface->altsetting->desc.bInterfaceNumber;

/* Get the interface/port specification from either driver_info or from
@@ -2895,10 +2904,6 @@ static int hso_probe(struct usb_interface *interface,
else
port_spec = hso_get_config_data(interface);

- if (interface->cur_altsetting->desc.bInterfaceClass != 0xFF) {
- dev_err(&interface->dev, "Not our interface\n");
- return -ENODEV;
- }
/* Check if we need to switch to alt interfaces prior to port
* configuration */
if (interface->num_altsetting > 1)
--
1.7.9.5


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