[PATCH 4.4 37/47] usb: max-3421: Prevent corruption of freed memory

Greg Kroah-Hartman
2021-07-26T15:41:59Z

From: Mark Tomlinson <mark.tomlinson@alliedtelesis.co.nz>

commit b5fdf5c6e6bee35837e160c00ac89327bdad031b upstream.

The MAX-3421 USB driver remembers the state of the USB toggles for a
device/endpoint. To save SPI writes, this was only done when a new
device/endpoint was being used. Unfortunately, if the old device was
removed, this would cause writes to freed memory.

To fix this, a simpler scheme is used. The toggles are read from
hardware when a URB is completed, and the toggles are always written to
hardware when any URB transaction is started. This will cause a few more
SPI transactions, but no causes kernel panics.

Fixes: 2d53139f3162 ("Add support for using a MAX3421E chip as a host driver.")
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Mark Tomlinson <mark.tomlinson@alliedtelesis.co.nz>
Link: https://lore.kernel.org/r/20210625031456.8632-1-mark.tomlinson@alliedtelesis.co.nz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/usb/host/max3421-hcd.c | 44 +++++++++++++----------------------------
1 file changed, 14 insertions(+), 30 deletions(-)

--- a/drivers/usb/host/max3421-hcd.c
+++ b/drivers/usb/host/max3421-hcd.c
@@ -149,8 +149,6 @@ struct max3421_hcd {
*/
struct urb *curr_urb;
enum scheduling_pass sched_pass;
- struct usb_device *loaded_dev; /* dev that's loaded into the chip */
- int loaded_epnum; /* epnum whose toggles are loaded */
int urb_done; /* > 0 -> no errors, < 0: errno */
size_t curr_len;
u8 hien;
@@ -488,39 +486,17 @@ max3421_set_speed(struct usb_hcd *hcd, s
* Caller must NOT hold HCD spinlock.
*/
static void
-max3421_set_address(struct usb_hcd *hcd, struct usb_device *dev, int epnum,
- int force_toggles)
+max3421_set_address(struct usb_hcd *hcd, struct usb_device *dev, int epnum)
{
- struct max3421_hcd *max3421_hcd = hcd_to_max3421(hcd);
- int old_epnum, same_ep, rcvtog, sndtog;
- struct usb_device *old_dev;
+ int rcvtog, sndtog;
u8 hctl;

- old_dev = max3421_hcd->loaded_dev;
- old_epnum = max3421_hcd->loaded_epnum;
-
- same_ep = (dev == old_dev && epnum == old_epnum);
- if (same_ep && !force_toggles)
- return;
-
- if (old_dev && !same_ep) {
- /* save the old end-points toggles: */
- u8 hrsl = spi_rd8(hcd, MAX3421_REG_HRSL);
-
- rcvtog = (hrsl >> MAX3421_HRSL_RCVTOGRD_BIT) & 1;
- sndtog = (hrsl >> MAX3421_HRSL_SNDTOGRD_BIT) & 1;
-
- /* no locking: HCD (i.e., we) own toggles, don't we? */
- usb_settoggle(old_dev, old_epnum, 0, rcvtog);
- usb_settoggle(old_dev, old_epnum, 1, sndtog);
- }
/* setup new endpoint's toggle bits: */
rcvtog = usb_gettoggle(dev, epnum, 0);
sndtog = usb_gettoggle(dev, epnum, 1);
hctl = (BIT(rcvtog + MAX3421_HCTL_RCVTOG0_BIT) |
BIT(sndtog + MAX3421_HCTL_SNDTOG0_BIT));

- max3421_hcd->loaded_epnum = epnum;
spi_wr8(hcd, MAX3421_REG_HCTL, hctl);

/*
@@ -528,7 +504,6 @@ max3421_set_address(struct usb_hcd *hcd,
* address-assignment so it's best to just always load the
* address whenever the end-point changed/was forced.
*/
- max3421_hcd->loaded_dev = dev;
spi_wr8(hcd, MAX3421_REG_PERADDR, dev->devnum);
}

@@ -663,7 +638,7 @@ max3421_select_and_start_urb(struct usb_
struct max3421_hcd *max3421_hcd = hcd_to_max3421(hcd);
struct urb *urb, *curr_urb = NULL;
struct max3421_ep *max3421_ep;
- int epnum, force_toggles = 0;
+ int epnum;
struct usb_host_endpoint *ep;
struct list_head *pos;
unsigned long flags;
@@ -773,7 +748,6 @@ done:
usb_settoggle(urb->dev, epnum, 0, 1);
usb_settoggle(urb->dev, epnum, 1, 1);
max3421_ep->pkt_state = PKT_STATE_SETUP;
- force_toggles = 1;
} else
max3421_ep->pkt_state = PKT_STATE_TRANSFER;
}
@@ -781,7 +755,7 @@ done:
spin_unlock_irqrestore(&max3421_hcd->lock, flags);

max3421_ep->last_active = max3421_hcd->frame_number;
- max3421_set_address(hcd, urb->dev, epnum, force_toggles);
+ max3421_set_address(hcd, urb->dev, epnum);
max3421_set_speed(hcd, urb->dev);
max3421_next_transfer(hcd, 0);
return 1;
@@ -1382,6 +1356,16 @@ max3421_urb_done(struct usb_hcd *hcd)
status = 0;
urb = max3421_hcd->curr_urb;
if (urb) {
+ /* save the old end-points toggles: */
+ u8 hrsl = spi_rd8(hcd, MAX3421_REG_HRSL);
+ int rcvtog = (hrsl >> MAX3421_HRSL_RCVTOGRD_BIT) & 1;
+ int sndtog = (hrsl >> MAX3421_HRSL_SNDTOGRD_BIT) & 1;
+ int epnum = usb_endpoint_num(&urb->ep->desc);
+
+ /* no locking: HCD (i.e., we) own toggles, don't we? */
+ usb_settoggle(urb->dev, epnum, 0, rcvtog);
+ usb_settoggle(urb->dev, epnum, 1, sndtog);
+
max3421_hcd->curr_urb = NULL;
spin_lock_irqsave(&max3421_hcd->lock, flags);
usb_hcd_unlink_urb_from_ep(hcd, urb);