HID: core: Sanitize event code and type when mapping input

commit 35556bed836f8dc07ac55f69c8d17dce3e7f0e25 upstream.

When calling into hid_map_usage(), the passed event code is
blindly stored as is, even if it doesn't fit in the associated bitmap.

This event code can come from a variety of sources, including devices
masquerading as input devices, only a bit more "programmable".

Instead of taking the event code at face value, check that it actually
fits the corresponding bitmap, and if it doesn't:
- spit out a warning so that we know which device is acting up
- NULLify the bitmap pointer so that we catch unexpected uses

Code paths that can make use of untrusted inputs can now check
that the mapping was indeed correct and bail out if not.

Mot-CRs-fixed: (CR)
CVE-Fixed: CVE-2020-0465
Bug: 162844689

Cc: stable@vger.kernel.org
Signed-off-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Change-Id: Ida234c943583d8b0274e1eff8bf419ba18978191
Signed-off-by: Jignesh Patel <jignesh@motorola.com>
Reviewed-on: https://gerrit.mot.com/1796758
SME-Granted: SME Approvals Granted
SLTApproved: Slta Waiver
Tested-by: Jira Key
Reviewed-by: Xiangpo Zhao <zhaoxp3@motorola.com>
Submit-Approved: Jira Key

diff --git a/drivers/hid/hid-input.c b/drivers/hid/hid-input.c
index a9c4a34746f3e5549727d4419edf73271c9ed5f5..385db19d0cdad6e70c7eb68920e2688061f869a4 100644 (file)
--- a/drivers/hid/hid-input.c
+++ b/drivers/hid/hid-input.c
@@ -1100,6 +1100,10 @@ static void hidinput_configure_usage(struct hid_input *hidinput, struct hid_fiel
        }
 
 mapped:
+       /* Mapping failed, bail out */
+       if (!bit)
+               return;
+
        if (device->driver->input_mapped && device->driver->input_mapped(device,
                                hidinput, field, usage, &bit, &max) < 0)
                goto ignore;

diff --git a/drivers/hid/hid-multitouch.c b/drivers/hid/hid-multitouch.c
index 07d92d4a9f7c8ca4a6bb4b93f4a08237d220aae1..2f7e2c018ddbf3f63ee697dbbf8198bf4eefa80c 100644 (file)
--- a/drivers/hid/hid-multitouch.c
+++ b/drivers/hid/hid-multitouch.c
@@ -616,6 +616,8 @@ static int mt_touch_input_mapping(struct hid_device *hdev, struct hid_input *hi,
                    (usage->hid & HID_USAGE) > 1)
                        code--;
                hid_map_usage(hi, usage, bit, max, EV_KEY, code);
+               if (!*bit)
+                       return -1;
                input_set_capability(hi->input, EV_KEY, code);
                return 1;
 

diff --git a/include/linux/hid.h b/include/linux/hid.h
index 06e6e04e6c11cb1009fb136637daaaba5264e485..7ab7c59e480d2edd932f1eec8cbb8929dcaae756 100644 (file)
--- a/include/linux/hid.h
+++ b/include/linux/hid.h
@@ -918,34 +918,49 @@ static inline void hid_device_io_stop(struct hid_device *hid) {
  * @max: maximal valid usage->code to consider later (out parameter)
  * @type: input event type (EV_KEY, EV_REL, ...)
  * @c: code which corresponds to this usage and type
+ *
+ * The value pointed to by @bit will be set to NULL if either @type is
+ * an unhandled event type, or if @c is out of range for @type. This
+ * can be used as an error condition.
  */
 static inline void hid_map_usage(struct hid_input *hidinput,
                struct hid_usage *usage, unsigned long **bit, int *max,
-               __u8 type, __u16 c)
+               __u8 type, unsigned int c)
 {
        struct input_dev *input = hidinput->input;
-
-       usage->type = type;
-       usage->code = c;
+       unsigned long *bmap = NULL;
+       unsigned int limit = 0;
 
        switch (type) {
        case EV_ABS:
-               *bit = input->absbit;
-               *max = ABS_MAX;
+               bmap = input->absbit;
+               limit = ABS_MAX;
                break;
        case EV_REL:
-               *bit = input->relbit;
-               *max = REL_MAX;
+               bmap = input->relbit;
+               limit = REL_MAX;
                break;
        case EV_KEY:
-               *bit = input->keybit;
-               *max = KEY_MAX;
+               bmap = input->keybit;
+               limit = KEY_MAX;
                break;
        case EV_LED:
-               *bit = input->ledbit;
-               *max = LED_MAX;
+               bmap = input->ledbit;
+               limit = LED_MAX;
                break;
        }
+
+       if (unlikely(c > limit || !bmap)) {
+               pr_warn_ratelimited("%s: Invalid code %d type %d\n",
+                                   input->name, c, type);
+               *bit = NULL;
+               return;
+       }
+
+       usage->type = type;
+       usage->code = c;
+       *max = limit;
+       *bit = bmap;
 }
 
 /**
@@ -959,7 +974,8 @@ static inline void hid_map_usage_clear(struct hid_input *hidinput,
                __u8 type, __u16 c)
 {
        hid_map_usage(hidinput, usage, bit, max, type, c);
-       clear_bit(c, *bit);
+       if (*bit)
+               clear_bit(usage->code, *bit);
 }
 
 /**