svn commit: r361921 - in stable/10: lib/libusbhid sys/dev/usb

[Hans Petter Selasky]

Author: hselasky
Date: Mon Jun  8 09:34:16 2020
New Revision: 361921
URL: https://svnweb.freebsd.org/changeset/base/361921

Log:
  MFC r361827:
  USB HID descriptors may push/pop the current state to allow
  description of items residing in a so-called union. FreeBSD currently
  only supports 4 such push levels.
  
  If the push level is not restored within the processing of the same
  HID item, an invalid memory location may be used for subsequent HID
  item processing.
  
  Verify that the push level is always valid when processing HID items.
  
  Reported by:	Andy Nguyen (Google)
  Sponsored by:	Mellanox Technologies

Modified:
  stable/10/lib/libusbhid/parse.c
  stable/10/sys/dev/usb/usb_hid.c
Directory Properties:
  stable/10/   (props changed)

Modified: stable/10/lib/libusbhid/parse.c
==============================================================================
--- stable/10/lib/libusbhid/parse.c	Mon Jun  8 09:33:45 2020	(r361920)
+++ stable/10/lib/libusbhid/parse.c	Mon Jun  8 09:34:16 2020	(r361921)
@@ -401,26 +401,28 @@ hid_get_item_raw(hid_data_t s, hid_item_t *h)
 				s->loc_count = dval & mask;
 				break;
 			case 10:	/* Push */
+				/* stop parsing, if invalid push level */
+				if ((s->pushlevel + 1) >= MAXPUSH)
+					return (0);
 				s->pushlevel ++;
-				if (s->pushlevel < MAXPUSH) {
-					s->cur[s->pushlevel] = *c;
-					/* store size and count */
-					c->report_size = s->loc_size;
-					c->report_count = s->loc_count;
-					/* update current item pointer */
-					c = &s->cur[s->pushlevel];
-				}
+				s->cur[s->pushlevel] = *c;
+				/* store size and count */
+				c->report_size = s->loc_size;
+				c->report_count = s->loc_count;
+				/* update current item pointer */
+				c = &s->cur[s->pushlevel];
 				break;
 			case 11:	/* Pop */
+				/* stop parsing, if invalid push level */
+				if (s->pushlevel == 0)
+					return (0);
 				s->pushlevel --;
-				if (s->pushlevel < MAXPUSH) {
-					c = &s->cur[s->pushlevel];
-					/* restore size and count */
-					s->loc_size = c->report_size;
-					s->loc_count = c->report_count;
-					c->report_size = 0;
-					c->report_count = 0;
-				}
+				c = &s->cur[s->pushlevel];
+				/* restore size and count */
+				s->loc_size = c->report_size;
+				s->loc_count = c->report_count;
+				c->report_size = 0;
+				c->report_count = 0;
 				break;
 			default:
 				break;

Modified: stable/10/sys/dev/usb/usb_hid.c
==============================================================================
--- stable/10/sys/dev/usb/usb_hid.c	Mon Jun  8 09:33:45 2020	(r361920)
+++ stable/10/sys/dev/usb/usb_hid.c	Mon Jun  8 09:34:16 2020	(r361921)
@@ -434,36 +434,36 @@ hid_get_item(struct hid_data *s, struct hid_item *h)
 				s->loc_count = dval & mask;
 				break;
 			case 10:	/* Push */
-				s->pushlevel ++;
-				if (s->pushlevel < MAXPUSH) {
-					s->cur[s->pushlevel] = *c;
-					/* store size and count */
-					c->loc.size = s->loc_size;
-					c->loc.count = s->loc_count;
-					/* update current item pointer */
-					c = &s->cur[s->pushlevel];
-				} else {
-					DPRINTFN(0, "Cannot push "
-					    "item @ %d\n", s->pushlevel);
+				/* stop parsing, if invalid push level */
+				if ((s->pushlevel + 1) >= MAXPUSH) {
+					DPRINTFN(0, "Cannot push item @ %d\n", s->pushlevel);
+					return (0);
 				}
+				s->pushlevel ++;
+				s->cur[s->pushlevel] = *c;
+				/* store size and count */
+				c->loc.size = s->loc_size;
+				c->loc.count = s->loc_count;
+				/* update current item pointer */
+				c = &s->cur[s->pushlevel];
 				break;
 			case 11:	/* Pop */
-				s->pushlevel --;
-				if (s->pushlevel < MAXPUSH) {
-					/* preserve position */
-					oldpos = c->loc.pos;
-					c = &s->cur[s->pushlevel];
-					/* restore size and count */
-					s->loc_size = c->loc.size;
-					s->loc_count = c->loc.count;
-					/* set default item location */
-					c->loc.pos = oldpos;
-					c->loc.size = 0;
-					c->loc.count = 0;
-				} else {
-					DPRINTFN(0, "Cannot pop "
-					    "item @ %d\n", s->pushlevel);
+				/* stop parsing, if invalid push level */
+				if (s->pushlevel == 0) {
+					DPRINTFN(0, "Cannot pop item @ 0\n");
+					return (0);
 				}
+				s->pushlevel --;
+				/* preserve position */
+				oldpos = c->loc.pos;
+				c = &s->cur[s->pushlevel];
+				/* restore size and count */
+				s->loc_size = c->loc.size;
+				s->loc_count = c->loc.count;
+				/* set default item location */
+				c->loc.pos = oldpos;
+				c->loc.size = 0;
+				c->loc.count = 0;
 				break;
 			default:
 				DPRINTFN(0, "Global bTag=%d\n", bTag);