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usb: devio: Add ioctl to disallow detaching kernel USB drivers.
The new USBDEVFS_DROP_PRIVILEGES ioctl allows a process to voluntarily
relinquish the ability to issue other ioctls that may interfere with
other processes and drivers that have claimed an interface on the
device.
This commit also includes a simple utility to be able to test the
ioctl, located at Documentation/usb/usbdevfs-drop-permissions.c
Example (with qemu-kvm's input device):
$ lsusb
...
Bus 001 Device 002: ID 0627:0001 Adomax Technology Co., Ltd
$ usb-devices
...
C: #Ifs= 1 Cfg#= 1 Atr=a0 MxPwr=100mA
I: If#= 0 Alt= 0 #EPs= 1 Cls=03(HID ) Sub=00 Prot=02 Driver=usbhid
$ sudo ./usbdevfs-drop-permissions /dev/bus/usb/001/002
OK: privileges dropped!
Available options:
[0] Exit now
[1] Reset device. Should fail if device is in use
[2] Claim 4 interfaces. Should succeed where not in use
[3] Narrow interface permission mask
Which option shall I run?: 1
ERROR: USBDEVFS_RESET failed! (1 - Operation not permitted)
Which test shall I run next?: 2
ERROR claiming if 0 (1 - Operation not permitted)
ERROR claiming if 1 (1 - Operation not permitted)
ERROR claiming if 2 (1 - Operation not permitted)
ERROR claiming if 3 (1 - Operation not permitted)
Which test shall I run next?: 0
After unbinding usbhid:
$ usb-devices
...
I: If#= 0 Alt= 0 #EPs= 1 Cls=03(HID ) Sub=00 Prot=02 Driver=(none)
$ sudo ./usbdevfs-drop-permissions /dev/bus/usb/001/002
...
Which option shall I run?: 2
OK: claimed if 0
ERROR claiming if 1 (1 - Operation not permitted)
ERROR claiming if 2 (1 - Operation not permitted)
ERROR claiming if 3 (1 - Operation not permitted)
Which test shall I run next?: 1
OK: USBDEVFS_RESET succeeded
Which test shall I run next?: 0
After unbinding usbhid and restricting the mask:
$ sudo ./usbdevfs-drop-permissions /dev/bus/usb/001/002
...
Which option shall I run?: 3
Insert new mask: 0
OK: privileges dropped!
Which test shall I run next?: 2
ERROR claiming if 0 (1 - Operation not permitted)
ERROR claiming if 1 (1 - Operation not permitted)
ERROR claiming if 2 (1 - Operation not permitted)
ERROR claiming if 3 (1 - Operation not permitted)
Signed-off-by: Reilly Grant <reillyg@chromium.org>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Emilio López <emilio.lopez@collabora.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Reilly Grant
Greg Kroah-Hartman
parent
3d0712deb0
commit
d883f52e1f
@ -732,6 +732,18 @@ usbdev_ioctl (int fd, int ifno, unsigned request, void *param)
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or SET_INTERFACE.
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</para></warning></listitem></varlistentry>
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<varlistentry><term>USBDEVFS_DROP_PRIVILEGES</term>
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<listitem><para>This is used to relinquish the ability
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to do certain operations which are considered to be
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privileged on a usbfs file descriptor.
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This includes claiming arbitrary interfaces, resetting
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a device on which there are currently claimed interfaces
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from other users, and issuing USBDEVFS_IOCTL calls.
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The ioctl parameter is a 32 bit mask of interfaces
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the user is allowed to claim on this file descriptor.
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You may issue this ioctl more than one time to narrow
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said mask.
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</para></listitem></varlistentry>
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</variablelist>
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</sect2>
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120
Documentation/usb/usbdevfs-drop-permissions.c
Normal file
120
Documentation/usb/usbdevfs-drop-permissions.c
Normal file
@ -0,0 +1,120 @@
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#include <sys/ioctl.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <fcntl.h>
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#include <stdio.h>
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#include <errno.h>
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#include <string.h>
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#include <inttypes.h>
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#include <unistd.h>
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#include <linux/usbdevice_fs.h>
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/* For building without an updated set of headers */
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#ifndef USBDEVFS_DROP_PRIVILEGES
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#define USBDEVFS_DROP_PRIVILEGES _IOW('U', 30, __u32)
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#define USBDEVFS_CAP_DROP_PRIVILEGES 0x40
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#endif
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void drop_privileges(int fd, uint32_t mask)
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{
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int res;
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res = ioctl(fd, USBDEVFS_DROP_PRIVILEGES, &mask);
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if (res)
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printf("ERROR: USBDEVFS_DROP_PRIVILEGES returned %d\n", res);
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else
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printf("OK: privileges dropped!\n");
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}
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void reset_device(int fd)
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{
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int res;
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res = ioctl(fd, USBDEVFS_RESET);
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if (!res)
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printf("OK: USBDEVFS_RESET succeeded\n");
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else
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printf("ERROR: reset failed! (%d - %s)\n",
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-res, strerror(-res));
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}
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void claim_some_intf(int fd)
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{
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int i, res;
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for (i = 0; i < 4; i++) {
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res = ioctl(fd, USBDEVFS_CLAIMINTERFACE, &i);
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if (!res)
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printf("OK: claimed if %d\n", i);
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else
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printf("ERROR claiming if %d (%d - %s)\n",
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i, -res, strerror(-res));
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}
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}
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int main(int argc, char *argv[])
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{
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uint32_t mask, caps;
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int c, fd;
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fd = open(argv[1], O_RDWR);
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if (fd < 0) {
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printf("Failed to open file\n");
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goto err_fd;
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}
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/*
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* check if dropping privileges is supported,
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* bail on systems where the capability is not present
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*/
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ioctl(fd, USBDEVFS_GET_CAPABILITIES, &caps);
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if (!(caps & USBDEVFS_CAP_DROP_PRIVILEGES)) {
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printf("DROP_PRIVILEGES not supported\n");
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goto err;
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}
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/*
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* Drop privileges but keep the ability to claim all
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* free interfaces (i.e., those not used by kernel drivers)
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*/
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drop_privileges(fd, -1U);
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printf("Available options:\n"
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"[0] Exit now\n"
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"[1] Reset device. Should fail if device is in use\n"
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"[2] Claim 4 interfaces. Should succeed where not in use\n"
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"[3] Narrow interface permission mask\n"
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"Which option shall I run?: ");
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while (scanf("%d", &c) == 1) {
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switch (c) {
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case 0:
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goto exit;
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case 1:
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reset_device(fd);
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break;
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case 2:
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claim_some_intf(fd);
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break;
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case 3:
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printf("Insert new mask: ");
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scanf("%x", &mask);
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drop_privileges(fd, mask);
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break;
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default:
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printf("I don't recognize that\n");
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}
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printf("Which test shall I run next?: ");
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}
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exit:
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close(fd);
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return 0;
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err:
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close(fd);
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err_fd:
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return 1;
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}
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@ -79,6 +79,8 @@ struct usb_dev_state {
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unsigned long ifclaimed;
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u32 secid;
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u32 disabled_bulk_eps;
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bool privileges_dropped;
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unsigned long interface_allowed_mask;
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};
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struct usb_memory {
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@ -748,6 +750,10 @@ static int claimintf(struct usb_dev_state *ps, unsigned int ifnum)
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if (test_bit(ifnum, &ps->ifclaimed))
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return 0;
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if (ps->privileges_dropped &&
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!test_bit(ifnum, &ps->interface_allowed_mask))
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return -EACCES;
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intf = usb_ifnum_to_if(dev, ifnum);
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if (!intf)
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err = -ENOENT;
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@ -985,7 +991,7 @@ static int usbdev_open(struct inode *inode, struct file *file)
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int ret;
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ret = -ENOMEM;
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ps = kmalloc(sizeof(struct usb_dev_state), GFP_KERNEL);
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ps = kzalloc(sizeof(struct usb_dev_state), GFP_KERNEL);
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if (!ps)
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goto out_free_ps;
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@ -1013,17 +1019,15 @@ static int usbdev_open(struct inode *inode, struct file *file)
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ps->dev = dev;
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ps->file = file;
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ps->interface_allowed_mask = 0xFFFFFFFF; /* 32 bits */
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spin_lock_init(&ps->lock);
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INIT_LIST_HEAD(&ps->list);
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INIT_LIST_HEAD(&ps->async_pending);
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INIT_LIST_HEAD(&ps->async_completed);
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INIT_LIST_HEAD(&ps->memory_list);
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init_waitqueue_head(&ps->wait);
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ps->discsignr = 0;
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ps->disc_pid = get_pid(task_pid(current));
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ps->cred = get_current_cred();
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ps->disccontext = NULL;
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ps->ifclaimed = 0;
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security_task_getsecid(current, &ps->secid);
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smp_wmb();
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list_add_tail(&ps->list, &dev->filelist);
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@ -1324,6 +1328,28 @@ static int proc_connectinfo(struct usb_dev_state *ps, void __user *arg)
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static int proc_resetdevice(struct usb_dev_state *ps)
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{
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struct usb_host_config *actconfig = ps->dev->actconfig;
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struct usb_interface *interface;
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int i, number;
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/* Don't allow a device reset if the process has dropped the
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* privilege to do such things and any of the interfaces are
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* currently claimed.
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*/
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if (ps->privileges_dropped && actconfig) {
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for (i = 0; i < actconfig->desc.bNumInterfaces; ++i) {
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interface = actconfig->interface[i];
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number = interface->cur_altsetting->desc.bInterfaceNumber;
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if (usb_interface_claimed(interface) &&
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!test_bit(number, &ps->ifclaimed)) {
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dev_warn(&ps->dev->dev,
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"usbfs: interface %d claimed by %s while '%s' resets device\n",
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number, interface->dev.driver->name, current->comm);
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return -EACCES;
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}
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}
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}
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return usb_reset_device(ps->dev);
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}
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@ -2090,6 +2116,9 @@ static int proc_ioctl(struct usb_dev_state *ps, struct usbdevfs_ioctl *ctl)
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struct usb_interface *intf = NULL;
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struct usb_driver *driver = NULL;
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if (ps->privileges_dropped)
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return -EACCES;
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/* alloc buffer */
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size = _IOC_SIZE(ctl->ioctl_code);
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if (size > 0) {
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@ -2215,7 +2244,8 @@ static int proc_get_capabilities(struct usb_dev_state *ps, void __user *arg)
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__u32 caps;
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caps = USBDEVFS_CAP_ZERO_PACKET | USBDEVFS_CAP_NO_PACKET_SIZE_LIM |
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USBDEVFS_CAP_REAP_AFTER_DISCONNECT | USBDEVFS_CAP_MMAP;
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USBDEVFS_CAP_REAP_AFTER_DISCONNECT | USBDEVFS_CAP_MMAP |
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USBDEVFS_CAP_DROP_PRIVILEGES;
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if (!ps->dev->bus->no_stop_on_short)
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caps |= USBDEVFS_CAP_BULK_CONTINUATION;
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if (ps->dev->bus->sg_tablesize)
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@ -2242,6 +2272,9 @@ static int proc_disconnect_claim(struct usb_dev_state *ps, void __user *arg)
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if (intf->dev.driver) {
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struct usb_driver *driver = to_usb_driver(intf->dev.driver);
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if (ps->privileges_dropped)
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return -EACCES;
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if ((dc.flags & USBDEVFS_DISCONNECT_CLAIM_IF_DRIVER) &&
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strncmp(dc.driver, intf->dev.driver->name,
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sizeof(dc.driver)) != 0)
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@ -2298,6 +2331,23 @@ static int proc_free_streams(struct usb_dev_state *ps, void __user *arg)
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return r;
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}
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static int proc_drop_privileges(struct usb_dev_state *ps, void __user *arg)
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{
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u32 data;
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if (copy_from_user(&data, arg, sizeof(data)))
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return -EFAULT;
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/* This is an one way operation. Once privileges are
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* dropped, you cannot regain them. You may however reissue
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* this ioctl to shrink the allowed interfaces mask.
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*/
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ps->interface_allowed_mask &= data;
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ps->privileges_dropped = true;
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return 0;
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}
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/*
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* NOTE: All requests here that have interface numbers as parameters
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* are assuming that somehow the configuration has been prevented from
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@ -2486,6 +2536,9 @@ static long usbdev_do_ioctl(struct file *file, unsigned int cmd,
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case USBDEVFS_FREE_STREAMS:
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ret = proc_free_streams(ps, p);
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break;
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case USBDEVFS_DROP_PRIVILEGES:
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ret = proc_drop_privileges(ps, p);
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break;
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}
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done:
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@ -135,6 +135,7 @@ struct usbdevfs_hub_portinfo {
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#define USBDEVFS_CAP_BULK_SCATTER_GATHER 0x08
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#define USBDEVFS_CAP_REAP_AFTER_DISCONNECT 0x10
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#define USBDEVFS_CAP_MMAP 0x20
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#define USBDEVFS_CAP_DROP_PRIVILEGES 0x40
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/* USBDEVFS_DISCONNECT_CLAIM flags & struct */
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@ -188,5 +189,6 @@ struct usbdevfs_streams {
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#define USBDEVFS_DISCONNECT_CLAIM _IOR('U', 27, struct usbdevfs_disconnect_claim)
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#define USBDEVFS_ALLOC_STREAMS _IOR('U', 28, struct usbdevfs_streams)
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#define USBDEVFS_FREE_STREAMS _IOR('U', 29, struct usbdevfs_streams)
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#define USBDEVFS_DROP_PRIVILEGES _IOW('U', 30, __u32)
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#endif /* _UAPI_LINUX_USBDEVICE_FS_H */
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