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authorHans de Goede <hdegoede@redhat.com>2017-10-16 17:21:19 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-10-17 11:53:20 +0300
commit845d584f41eac3475c21e4a7d5e88d0f6e410cf7 (patch)
tree5aa1a5a99b4e41160a50917f84aaf36046188117 /drivers/usb
parent283776e9b72502c71c34f489e1015841bd8681ab (diff)
downloadlinux-845d584f41eac3475c21e4a7d5e88d0f6e410cf7.tar.xz
USB: devio: Revert "USB: devio: Don't corrupt user memory"
Taking the uurb->buffer_length userspace passes in as a maximum for the actual urbs transfer_buffer_length causes 2 serious issues: 1) It breaks isochronous support for all userspace apps using libusb, as existing libusb versions pass in 0 for uurb->buffer_length, relying on the kernel using the lenghts of the usbdevfs_iso_packet_desc descriptors passed in added together as buffer length. This for example causes redirection of USB audio and Webcam's into virtual machines using qemu-kvm to no longer work. This is a userspace ABI break and as such must be reverted. Note that the original commit does not protect other users / the kernels memory, it only stops the userspace process making the call from shooting itself in the foot. 2) It may cause the kernel to program host controllers to DMA over random memory. Just as the devio code used to only look at the iso_packet_desc lenghts, the host drivers do the same, relying on the submitter of the urbs to make sure the entire buffer is large enough and not checking transfer_buffer_length. But the "USB: devio: Don't corrupt user memory" commit now takes the userspace provided uurb->buffer_length for the buffer-size while copying over the user-provided iso_packet_desc lengths 1:1, allowing the user to specify a small buffer size while programming the host controller to dma a lot more data. (Atleast the ohci, uhci, xhci and fhci drivers do not check transfer_buffer_length for isoc transfers.) This reverts commit fa1ed74eb1c2 ("USB: devio: Don't corrupt user memory") fixing both these issues. Cc: Dan Carpenter <dan.carpenter@oracle.com> Cc: stable@vger.kernel.org Signed-off-by: Hans de Goede <hdegoede@redhat.com> Acked-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/usb')
-rw-r--r--drivers/usb/core/devio.c6
1 files changed, 1 insertions, 5 deletions
diff --git a/drivers/usb/core/devio.c b/drivers/usb/core/devio.c
index 4664e543cf2f..e9326f31db8d 100644
--- a/drivers/usb/core/devio.c
+++ b/drivers/usb/core/devio.c
@@ -1576,11 +1576,7 @@ static int proc_do_submiturb(struct usb_dev_state *ps, struct usbdevfs_urb *uurb
totlen += isopkt[u].length;
}
u *= sizeof(struct usb_iso_packet_descriptor);
- if (totlen <= uurb->buffer_length)
- uurb->buffer_length = totlen;
- else
- WARN_ONCE(1, "uurb->buffer_length is too short %d vs %d",
- totlen, uurb->buffer_length);
+ uurb->buffer_length = totlen;
break;
default: