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Date: Thu, 7 Dec 2017 13:48:37 +0100 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: linux-kernel@...r.kernel.org Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, stable@...r.kernel.org, Dan Carpenter <dan.carpenter@...cle.com>, Alan Stern <stern@...land.harvard.edu> Subject: [PATCH 3.18 24/26] USB: devio: Prevent integer overflow in proc_do_submiturb() 3.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Dan Carpenter <dan.carpenter@...cle.com> commit 57999d1107c1e60c2ca7088f2ac0f819e2f554b3 upstream. There used to be an integer overflow check in proc_do_submiturb() but we removed it. It turns out that it's still required. The uurb->buffer_length variable is a signed integer and it's controlled by the user. It can lead to an integer overflow when we do: num_sgs = DIV_ROUND_UP(uurb->buffer_length, USB_SG_SIZE); If we strip away the macro then that line looks like this: num_sgs = (uurb->buffer_length + USB_SG_SIZE - 1) / USB_SG_SIZE; ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ It's the first addition which can overflow. Fixes: 1129d270cbfb ("USB: Increase usbfs transfer limit") Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com> Acked-by: Alan Stern <stern@...land.harvard.edu> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org> --- drivers/usb/core/devio.c | 5 +++++ 1 file changed, 5 insertions(+) --- a/drivers/usb/core/devio.c +++ b/drivers/usb/core/devio.c @@ -118,6 +118,9 @@ 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 atomic64_t usbfs_memory_usage; /* Total memory currently allocated */ /* Check whether it's okay to allocate more memory for a transfer */ @@ -1295,6 +1298,8 @@ static int proc_do_submiturb(struct usb_ USBDEVFS_URB_ZERO_PACKET | USBDEVFS_URB_NO_INTERRUPT)) return -EINVAL; + if ((unsigned int)uurb->buffer_length >= USBFS_XFER_MAX) + return -EINVAL; if (uurb->buffer_length > 0 && !uurb->buffer) return -EINVAL; if (!(uurb->type == USBDEVFS_URB_TYPE_CONTROL &&
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