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Subject[PATCH 3.18 23/26] USB: Increase usbfs transfer limit
Date
3.18-stable review patch.  If anyone has any objections, please let me know.

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

From: Mateusz Berezecki <mateuszb@fastmail.fm>

commit 1129d270cbfbb7e2b1ec3dede4a13930bdd10e41 upstream.

Promote a variable keeping track of USB transfer memory usage to a
wider data type and allow for higher bandwidth transfers from a large
number of USB devices connected to a single host.

Signed-off-by: Mateusz Berezecki <mateuszb@fastmail.fm>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/usb/core/devio.c | 43 ++++++++++++++++---------------------------
1 file changed, 16 insertions(+), 27 deletions(-)

--- a/drivers/usb/core/devio.c
+++ b/drivers/usb/core/devio.c
@@ -113,42 +113,35 @@ enum snoop_when {
#define USB_DEVICE_DEV MKDEV(USB_DEVICE_MAJOR, 0)

/* Limit on the total amount of memory we can allocate for transfers */
-static unsigned usbfs_memory_mb = 16;
+static u32 usbfs_memory_mb = 16;
module_param(usbfs_memory_mb, uint, 0644);
MODULE_PARM_DESC(usbfs_memory_mb,
"maximum MB allowed for usbfs buffers (0 = no limit)");

-/* Hard limit, necessary to avoid arithmetic overflow */
-#define USBFS_XFER_MAX (UINT_MAX / 2 - 1000000)
-
-static atomic_t usbfs_memory_usage; /* Total memory currently allocated */
+static atomic64_t usbfs_memory_usage; /* Total memory currently allocated */

/* Check whether it's okay to allocate more memory for a transfer */
-static int usbfs_increase_memory_usage(unsigned amount)
+static int usbfs_increase_memory_usage(u64 amount)
{
- unsigned lim;
+ u64 lim;

- /*
- * Convert usbfs_memory_mb to bytes, avoiding overflows.
- * 0 means use the hard limit (effectively unlimited).
- */
lim = ACCESS_ONCE(usbfs_memory_mb);
- if (lim == 0 || lim > (USBFS_XFER_MAX >> 20))
- lim = USBFS_XFER_MAX;
- else
- lim <<= 20;
+ lim <<= 20;

- atomic_add(amount, &usbfs_memory_usage);
- if (atomic_read(&usbfs_memory_usage) <= lim)
- return 0;
- atomic_sub(amount, &usbfs_memory_usage);
- return -ENOMEM;
+ atomic64_add(amount, &usbfs_memory_usage);
+
+ if (lim > 0 && atomic64_read(&usbfs_memory_usage) > lim) {
+ atomic64_sub(amount, &usbfs_memory_usage);
+ return -ENOMEM;
+ }
+
+ return 0;
}

/* Memory for a transfer is being deallocated */
-static void usbfs_decrease_memory_usage(unsigned amount)
+static void usbfs_decrease_memory_usage(u64 amount)
{
- atomic_sub(amount, &usbfs_memory_usage);
+ atomic64_sub(amount, &usbfs_memory_usage);
}

static int connected(struct usb_dev_state *ps)
@@ -1077,7 +1070,7 @@ static int proc_bulk(struct usb_dev_stat
if (!usb_maxpacket(dev, pipe, !(bulk.ep & USB_DIR_IN)))
return -EINVAL;
len1 = bulk.len;
- if (len1 >= USBFS_XFER_MAX)
+ if (len1 >= (INT_MAX - sizeof(struct urb)))
return -EINVAL;
ret = usbfs_increase_memory_usage(len1 + sizeof(struct urb));
if (ret)
@@ -1420,10 +1413,6 @@ static int proc_do_submiturb(struct usb_
return -EINVAL;
}

- if (uurb->buffer_length >= USBFS_XFER_MAX) {
- ret = -EINVAL;
- goto error;
- }
if (uurb->buffer_length > 0 &&
!access_ok(is_in ? VERIFY_WRITE : VERIFY_READ,
uurb->buffer, uurb->buffer_length)) {

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