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USB HID descriptors may push/pop the current state to allow

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description of items residing in a so-called union. FreeBSD currently
only supports 4 such pop 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)
MFC after:	3 days
Sponsored by:	Mellanox Technologies
This commit is contained in:
Hans Petter Selasky 2020-06-05 07:57:16 +00:00
parent 48f25cc3c2
commit eff8154913
2 changed files with 44 additions and 42 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
lib/libusbhid/parse.c
View File

@ -403,26 +403,28 @@ 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];
}
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;
}
break;
default:
break;

20
sys/dev/usb/usb_hid.c
View File

@ -436,22 +436,26 @@ hid_get_item(struct hid_data *s, struct hid_item *h)
s->loc_count = dval & mask;
break;
case 10: /* Push */
/* stop parsing, if invalid push level */
if ((s->pushlevel + 1) >= MAXPUSH) {
DPRINTFN(0, "Cannot push item @ %d\n", s->pushlevel);
return (0);
}
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);
}
break;
case 11: /* Pop */
/* stop parsing, if invalid push level */
if (s->pushlevel == 0) {
DPRINTFN(0, "Cannot pop item @ 0\n");
return (0);
}
s->pushlevel --;
if (s->pushlevel < MAXPUSH) {
/* preserve position */
oldpos = c->loc.pos;
c = &s->cur[s->pushlevel];
@ -462,10 +466,6 @@ hid_get_item(struct hid_data *s, struct hid_item *h)
c->loc.pos = oldpos;
c->loc.size = 0;
c->loc.count = 0;
} else {
DPRINTFN(0, "Cannot pop "
"item @ %d\n", s->pushlevel);
}
break;
default:
DPRINTFN(0, "Global bTag=%d\n", bTag);