On 7/2/19 11:45 AM, Greg KH wrote:
On Tue, Jul 02, 2019 at 07:49:26AM +0700, Phong Tran wrote:
Hello,

I did a checking for this report of syzbot [1]
 From the call stack of dump log:

There shows that a problem within technisat_usb2_get_ir()

BUG: KASAN: slab-out-of-bounds in technisat_usb2_get_ir
drivers/media/usb/dvb-usb/technisat-usb2.c:664 [inline]
BUG: KASAN: slab-out-of-bounds in technisat_usb2_rc_query+0x5fa/0x660
drivers/media/usb/dvb-usb/technisat-usb2.c:679
Read of size 1 at addr ffff8880a8791ea8 by task kworker/0:1/12

Take a look into while loop in technisat_usb2_get_ir().
I recognized that a problem. The loop will not break out with the condition
doesn't reach. Then "b++" will go wrong and buffer will be overflow.

while (1) {
[...]
        b++;
        if (*b == 0xff) {
                ev.pulse = 0;
                ev.duration = 888888*2;
                ir_raw_event_store(d->rc_dev, &ev);
                break;
        }
}

I would propose changing the loop condition by checking the address of the
buffer. If acceptable, I will send this patch to the mailing-list.
eg:

-       while (1) {
+       while (b != (buf + 63)) {
[...]
}

Tested with syzbot, result is good [2].

[1] https://syzkaller.appspot.com/bug?extid=eaaaf38a95427be88f4b
[2] https://groups.google.com/d/msg/syzkaller-bugs/CySBCKuUOOs/0hKq1CdjCwAJ

Great, can you submit a patch for this?


Yes, sent a patch
https://lore.kernel.org/lkml/20190702140211.28399-1-tranmanph...@gmail.com/

Phong.

thanks,

greg k-h

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