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Date: Wed, 11 Sep 2013 13:08:45 -0700
From: Kees Cook <keescook@...omium.org>
To: Benjamin Tissoires <benjamin.tissoires@...hat.com>
Cc: Benjamin Tissoires <benjamin.tissoires@...il.com>,
Henrik Rydberg <rydberg@...omail.se>,
Jiri Kosina <jkosina@...e.cz>,
linux-input <linux-input@...r.kernel.org>,
LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 08/10] HID: validate feature and input report details
On Wed, Sep 11, 2013 at 12:56 PM, Benjamin Tissoires
<benjamin.tissoires@...hat.com> wrote:
> When dealing with usage_index, be sure to properly use unsigned instead of
> int to avoid overflows.
>
> When working on report fields, always validate that their report_counts are
> in bounds.
> Without this, a HID device could report a malicious feature report that
> could trick the driver into a heap overflow:
>
> [ 634.885003] usb 1-1: New USB device found, idVendor=0596, idProduct=0500
> ...
> [ 676.469629] BUG kmalloc-192 (Tainted: G W ): Redzone overwritten
>
> CVE-2013-2897
>
> Cc: stable@...r.kernel.org
> Signed-off-by: Benjamin Tissoires <benjamin.tissoires@...hat.com>
Acked-by: Kees Cook <keescook@...omium.org>
> ---
> v3:
> - new patch: extract from the hid-multitouch patch, the generic checks so that
> every hid drivers will benefit from them
>
> drivers/hid/hid-core.c | 16 +++++++---------
> drivers/hid/hid-input.c | 11 ++++++++++-
> 2 files changed, 17 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
> index 44b6c68..329e24e 100644
> --- a/drivers/hid/hid-core.c
> +++ b/drivers/hid/hid-core.c
> @@ -94,7 +94,6 @@ EXPORT_SYMBOL_GPL(hid_register_report);
> static struct hid_field *hid_register_field(struct hid_report *report, unsigned usages, unsigned values)
> {
> struct hid_field *field;
> - int i;
>
> if (report->maxfield == HID_MAX_FIELDS) {
> hid_err(report->device, "too many fields in report\n");
> @@ -113,9 +112,6 @@ static struct hid_field *hid_register_field(struct hid_report *report, unsigned
> field->value = (s32 *)(field->usage + usages);
> field->report = report;
>
> - for (i = 0; i < usages; i++)
> - field->usage[i].usage_index = i;
> -
> return field;
> }
>
> @@ -226,9 +222,9 @@ static int hid_add_field(struct hid_parser *parser, unsigned report_type, unsign
> {
> struct hid_report *report;
> struct hid_field *field;
> - int usages;
> + unsigned usages;
> unsigned offset;
> - int i;
> + unsigned i;
>
> report = hid_register_report(parser->device, report_type, parser->global.report_id);
> if (!report) {
> @@ -255,7 +251,8 @@ static int hid_add_field(struct hid_parser *parser, unsigned report_type, unsign
> if (!parser->local.usage_index) /* Ignore padding fields */
> return 0;
>
> - usages = max_t(int, parser->local.usage_index, parser->global.report_count);
> + usages = max_t(unsigned, parser->local.usage_index,
> + parser->global.report_count);
>
> field = hid_register_field(report, usages, parser->global.report_count);
> if (!field)
> @@ -266,13 +263,14 @@ static int hid_add_field(struct hid_parser *parser, unsigned report_type, unsign
> field->application = hid_lookup_collection(parser, HID_COLLECTION_APPLICATION);
>
> for (i = 0; i < usages; i++) {
> - int j = i;
> + unsigned j = i;
> /* Duplicate the last usage we parsed if we have excess values */
> if (i >= parser->local.usage_index)
> j = parser->local.usage_index - 1;
> field->usage[i].hid = parser->local.usage[j];
> field->usage[i].collection_index =
> parser->local.collection_index[j];
> + field->usage[i].usage_index = i;
> }
>
> field->maxusage = usages;
> @@ -1354,7 +1352,7 @@ int hid_report_raw_event(struct hid_device *hid, int type, u8 *data, int size,
> goto out;
> }
>
> - if (hid->claimed != HID_CLAIMED_HIDRAW) {
> + if (hid->claimed != HID_CLAIMED_HIDRAW && report->maxfield) {
> for (a = 0; a < report->maxfield; a++)
> hid_input_field(hid, report->field[a], cdata, interrupt);
> hdrv = hid->driver;
> diff --git a/drivers/hid/hid-input.c b/drivers/hid/hid-input.c
> index b420f4a..8741d95 100644
> --- a/drivers/hid/hid-input.c
> +++ b/drivers/hid/hid-input.c
> @@ -485,6 +485,10 @@ static void hidinput_configure_usage(struct hid_input *hidinput, struct hid_fiel
> if (field->flags & HID_MAIN_ITEM_CONSTANT)
> goto ignore;
>
> + /* Ignore if report count is out of bounds. */
> + if (field->report_count < 1)
> + goto ignore;
> +
> /* only LED usages are supported in output fields */
> if (field->report_type == HID_OUTPUT_REPORT &&
> (usage->hid & HID_USAGE_PAGE) != HID_UP_LED) {
> @@ -1236,7 +1240,11 @@ static void report_features(struct hid_device *hid)
>
> rep_enum = &hid->report_enum[HID_FEATURE_REPORT];
> list_for_each_entry(rep, &rep_enum->report_list, list)
> - for (i = 0; i < rep->maxfield; i++)
> + for (i = 0; i < rep->maxfield; i++) {
> + /* Ignore if report count is out of bounds. */
> + if (rep->field[i]->report_count < 1)
> + continue;
> +
> for (j = 0; j < rep->field[i]->maxusage; j++) {
> /* Verify if Battery Strength feature is available */
> hidinput_setup_battery(hid, HID_FEATURE_REPORT, rep->field[i]);
> @@ -1245,6 +1253,7 @@ static void report_features(struct hid_device *hid)
> drv->feature_mapping(hid, rep->field[i],
> rep->field[i]->usage + j);
> }
> + }
> }
>
> static struct hid_input *hidinput_allocate(struct hid_device *hid)
> --
> 1.8.3.1
>
--
Kees Cook
Chrome OS Security
--
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