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authorReilly Grant <reillyg@chromium.org>2016-02-21 18:38:01 -0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2016-03-05 12:05:01 -0800
commitd883f52e1f6d2eca8378e3795f333c1396943873 (patch)
tree849a84ea953f7adf6869229156f1b6bd97a77f4b /Documentation/usb
parent3d0712deb0a416021e55febc7ec7f6c24f460e06 (diff)
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>
Diffstat (limited to 'Documentation/usb')
-rw-r--r--Documentation/usb/usbdevfs-drop-permissions.c120
1 files changed, 120 insertions, 0 deletions
diff --git a/Documentation/usb/usbdevfs-drop-permissions.c b/Documentation/usb/usbdevfs-drop-permissions.c
new file mode 100644
index 000000000000..6b8da6ef0c9a
--- /dev/null
+++ b/Documentation/usb/usbdevfs-drop-permissions.c
@@ -0,0 +1,120 @@
+#include <sys/ioctl.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <errno.h>
+#include <string.h>
+#include <inttypes.h>
+#include <unistd.h>
+
+#include <linux/usbdevice_fs.h>
+
+/* For building without an updated set of headers */
+#ifndef USBDEVFS_DROP_PRIVILEGES
+#define USBDEVFS_DROP_PRIVILEGES _IOW('U', 30, __u32)
+#define USBDEVFS_CAP_DROP_PRIVILEGES 0x40
+#endif
+
+void drop_privileges(int fd, uint32_t mask)
+{
+ int res;
+
+ res = ioctl(fd, USBDEVFS_DROP_PRIVILEGES, &mask);
+ if (res)
+ printf("ERROR: USBDEVFS_DROP_PRIVILEGES returned %d\n", res);
+ else
+ printf("OK: privileges dropped!\n");
+}
+
+void reset_device(int fd)
+{
+ int res;
+
+ res = ioctl(fd, USBDEVFS_RESET);
+ if (!res)
+ printf("OK: USBDEVFS_RESET succeeded\n");
+ else
+ printf("ERROR: reset failed! (%d - %s)\n",
+ -res, strerror(-res));
+}
+
+void claim_some_intf(int fd)
+{
+ int i, res;
+
+ for (i = 0; i < 4; i++) {
+ res = ioctl(fd, USBDEVFS_CLAIMINTERFACE, &i);
+ if (!res)
+ printf("OK: claimed if %d\n", i);
+ else
+ printf("ERROR claiming if %d (%d - %s)\n",
+ i, -res, strerror(-res));
+ }
+}
+
+int main(int argc, char *argv[])
+{
+ uint32_t mask, caps;
+ int c, fd;
+
+ fd = open(argv[1], O_RDWR);
+ if (fd < 0) {
+ printf("Failed to open file\n");
+ goto err_fd;
+ }
+
+ /*
+ * check if dropping privileges is supported,
+ * bail on systems where the capability is not present
+ */
+ ioctl(fd, USBDEVFS_GET_CAPABILITIES, &caps);
+ if (!(caps & USBDEVFS_CAP_DROP_PRIVILEGES)) {
+ printf("DROP_PRIVILEGES not supported\n");
+ goto err;
+ }
+
+ /*
+ * Drop privileges but keep the ability to claim all
+ * free interfaces (i.e., those not used by kernel drivers)
+ */
+ drop_privileges(fd, -1U);
+
+ printf("Available options:\n"
+ "[0] Exit now\n"
+ "[1] Reset device. Should fail if device is in use\n"
+ "[2] Claim 4 interfaces. Should succeed where not in use\n"
+ "[3] Narrow interface permission mask\n"
+ "Which option shall I run?: ");
+
+ while (scanf("%d", &c) == 1) {
+ switch (c) {
+ case 0:
+ goto exit;
+ case 1:
+ reset_device(fd);
+ break;
+ case 2:
+ claim_some_intf(fd);
+ break;
+ case 3:
+ printf("Insert new mask: ");
+ scanf("%x", &mask);
+ drop_privileges(fd, mask);
+ break;
+ default:
+ printf("I don't recognize that\n");
+ }
+
+ printf("Which test shall I run next?: ");
+ }
+
+exit:
+ close(fd);
+ return 0;
+
+err:
+ close(fd);
+err_fd:
+ return 1;
+}