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HID: hiddev: fix potential Spectre v1

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uref->usage_index can be indirectly controlled by userspace, hence leading
to a potential exploitation of the Spectre variant 1 vulnerability.

This field is used as an array index by the hiddev_ioctl_usage() function,
when 'cmd' is either HIDIOCGCOLLECTIONINDEX, HIDIOCGUSAGES or
HIDIOCSUSAGES.

For cmd == HIDIOCGCOLLECTIONINDEX case, uref->usage_index is compared to
field->maxusage and then used as an index to dereference field->usage
array. The same thing happens to the cmd == HIDIOC{G,S}USAGES cases, where
uref->usage_index is checked against an array maximum value and then it is
used as an index in an array.

This is a summary of the HIDIOCGCOLLECTIONINDEX case, which matches the
traditional Spectre V1 first load:

	copy_from_user(uref, user_arg, sizeof(*uref))
	if (uref->usage_index >= field->maxusage)
		goto inval;
	i = field->usage[uref->usage_index].collection_index;
	return i;

This patch fixes this by sanitizing field uref->usage_index before using it
to index field->usage (HIDIOCGCOLLECTIONINDEX) or field->value in
HIDIOC{G,S}USAGES arrays, thus, avoiding speculation in the first load.

Cc: <stable@vger.kernel.org>
Signed-off-by: Breno Leitao <leitao@debian.org>
--

v2: Contemplate cmd == HIDIOC{G,S}USAGES case
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
This commit is contained in:
Breno Leitao 2018-10-19 17:01:33 -03:00 committed by Jiri Kosina
parent 96f2f66a98
commit f11274396a
1 changed files with 14 additions and 4 deletions
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18
drivers/hid/usbhid/hiddev.c
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@ -512,14 +512,24 @@ static noinline int hiddev_ioctl_usage(struct hiddev *hiddev, unsigned int cmd,
if (cmd == HIDIOCGCOLLECTIONINDEX) {
if (uref->usage_index >= field->maxusage)
goto inval;
uref->usage_index =
array_index_nospec(uref->usage_index,
field->maxusage);
} else if (uref->usage_index >= field->report_count)
goto inval;
}
if ((cmd == HIDIOCGUSAGES || cmd == HIDIOCSUSAGES) &&
(uref_multi->num_values > HID_MAX_MULTI_USAGES ||
uref->usage_index + uref_multi->num_values > field->report_count))
goto inval;
if (cmd == HIDIOCGUSAGES || cmd == HIDIOCSUSAGES) {
if (uref_multi->num_values > HID_MAX_MULTI_USAGES ||
uref->usage_index + uref_multi->num_values >
field->report_count)
goto inval;
uref->usage_index =
array_index_nospec(uref->usage_index,
field->report_count -
uref_multi->num_values);
}
switch (cmd) {
case HIDIOCGUSAGE: