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SubjectRe: KASAN: slab-out-of-bounds Read in hid_field_extract
On Mon, 9 Dec 2019, syzbot wrote:

> Hello,
>
> syzbot has tested the proposed patch but the reproducer still triggered
> crash:
> KASAN: slab-out-of-bounds Read in hid_field_extract
>
> microsoft 0003:045E:07DA.0001: Report rsize 4096 csize 1
> microsoft 0003:045E:07DA.0001: Field offset 0 size 12 count 4899
> ==================================================================
> BUG: KASAN: slab-out-of-bounds in __extract drivers/hid/hid-core.c:1345
> [inline]
> BUG: KASAN: slab-out-of-bounds in hid_field_extract+0x150/0x170
> drivers/hid/hid-core.c:1365
> Read of size 1 at addr ffff8881cc759000 by task swapper/1/0

Nobody bothers to check for ridiculously long reports? This field had
report_size = 12 and report_count = 4899!

Alan Stern

#syz test: https://github.com/google/kasan.git 1f22d15c

Index: usb-devel/drivers/hid/hid-core.c
===================================================================
--- usb-devel.orig/drivers/hid/hid-core.c
+++ usb-devel/drivers/hid/hid-core.c
@@ -267,6 +267,10 @@ static int hid_add_field(struct hid_pars

offset = report->size;
report->size += parser->global.report_size * parser->global.report_count;
+ if (report->size > HID_MAX_BUFFER_SIZE << 3) {
+ hid_err(parser->device, "report is too long\n");
+ return -1;
+ }

if (!parser->local.usage_index) /* Ignore padding fields */
return 0;
@@ -1488,6 +1492,7 @@ static void hid_input_field(struct hid_d
if (!value)
return;

+ hid_info(hid, "Field offset %u size %u count %u\n", offset, size, count);
for (n = 0; n < count; n++) {

value[n] = min < 0 ?
@@ -1712,6 +1717,7 @@ int hid_report_raw_event(struct hid_devi
}

if (hid->claimed != HID_CLAIMED_HIDRAW && report->maxfield) {
+ hid_info(hid, "Report rsize %u csize %u\n", rsize, csize);
for (a = 0; a < report->maxfield; a++)
hid_input_field(hid, report->field[a], cdata, interrupt);
hdrv = hid->driver;


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