3.16.61-rc1 review patch. If anyone has any objections, please let me know.
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From: "Gustavo A. R. Silva" gustavo@embeddedor.com
commit 4f65245f2d178b9cba48350620d76faa4a098841 upstream.
uref->field_index, uref->usage_index, finfo.field_index and cinfo.index can be indirectly controlled by user-space, hence leading to a potential exploitation of the Spectre variant 1 vulnerability.
This issue was detected with the help of Smatch:
drivers/hid/usbhid/hiddev.c:473 hiddev_ioctl_usage() warn: potential spectre issue 'report->field' (local cap) drivers/hid/usbhid/hiddev.c:477 hiddev_ioctl_usage() warn: potential spectre issue 'field->usage' (local cap) drivers/hid/usbhid/hiddev.c:757 hiddev_ioctl() warn: potential spectre issue 'report->field' (local cap) drivers/hid/usbhid/hiddev.c:801 hiddev_ioctl() warn: potential spectre issue 'hid->collection' (local cap)
Fix this by sanitizing such structure fields before using them to index report->field, field->usage and hid->collection
Notice that given that speculation windows are large, the policy is to kill the speculation on the first load and not worry if it can be completed with a dependent load/store [1].
[1] https://marc.info/?l=linux-kernel&m=152449131114778&w=2
Signed-off-by: Gustavo A. R. Silva gustavo@embeddedor.com Signed-off-by: Jiri Kosina jkosina@suse.cz Signed-off-by: Ben Hutchings ben@decadent.org.uk --- drivers/hid/usbhid/hiddev.c | 11 +++++++++++ 1 file changed, 11 insertions(+)
--- a/drivers/hid/usbhid/hiddev.c +++ b/drivers/hid/usbhid/hiddev.c @@ -35,6 +35,7 @@ #include <linux/hiddev.h> #include <linux/compat.h> #include <linux/vmalloc.h> +#include <linux/nospec.h> #include "usbhid.h"
#ifdef CONFIG_USB_DYNAMIC_MINORS @@ -478,10 +479,14 @@ static noinline int hiddev_ioctl_usage(s
if (uref->field_index >= report->maxfield) goto inval; + uref->field_index = array_index_nospec(uref->field_index, + report->maxfield);
field = report->field[uref->field_index]; if (uref->usage_index >= field->maxusage) goto inval; + uref->usage_index = array_index_nospec(uref->usage_index, + field->maxusage);
uref->usage_code = field->usage[uref->usage_index].hid;
@@ -508,6 +513,8 @@ static noinline int hiddev_ioctl_usage(s
if (uref->field_index >= report->maxfield) goto inval; + uref->field_index = array_index_nospec(uref->field_index, + report->maxfield);
field = report->field[uref->field_index];
@@ -761,6 +768,8 @@ static long hiddev_ioctl(struct file *fi
if (finfo.field_index >= report->maxfield) break; + finfo.field_index = array_index_nospec(finfo.field_index, + report->maxfield);
field = report->field[finfo.field_index]; memset(&finfo, 0, sizeof(finfo)); @@ -801,6 +810,8 @@ static long hiddev_ioctl(struct file *fi
if (cinfo.index >= hid->maxcollection) break; + cinfo.index = array_index_nospec(cinfo.index, + hid->maxcollection);
cinfo.type = hid->collection[cinfo.index].type; cinfo.usage = hid->collection[cinfo.index].usage;