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author | Reilly Grant <reillyg@chromium.org> | 2016-02-22 00:38:01 +0300 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2016-03-05 23:05:01 +0300 |
commit | d883f52e1f6d2eca8378e3795f333c1396943873 (patch) | |
tree | 849a84ea953f7adf6869229156f1b6bd97a77f4b /Documentation/usb/usbdevfs-drop-permissions.c | |
parent | 3d0712deb0a416021e55febc7ec7f6c24f460e06 (diff) | |
download | linux-d883f52e1f6d2eca8378e3795f333c1396943873.tar.xz |
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/usbdevfs-drop-permissions.c')
-rw-r--r-- | Documentation/usb/usbdevfs-drop-permissions.c | 120 |
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; +} |