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SubjectRe: KMSAN: uninit-value in smsc75xx_bind
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Am Freitag, den 09.08.2019, 01:48 -0700 schrieb syzbot:
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit: beaab8a3 fix KASAN build
> git tree: kmsan

[..]
> Call Trace:
> __dump_stack lib/dump_stack.c:77 [inline]
> dump_stack+0x191/0x1f0 lib/dump_stack.c:113
> kmsan_report+0x162/0x2d0 mm/kmsan/kmsan_report.c:109
> __msan_warning+0x75/0xe0 mm/kmsan/kmsan_instr.c:294
> smsc75xx_wait_ready drivers/net/usb/smsc75xx.c:976 [inline]
> smsc75xx_bind+0x541/0x12d0 drivers/net/usb/smsc75xx.c:1483

>
> Local variable description: ----buf.i93@smsc75xx_bind
> Variable was created at:
> __smsc75xx_read_reg drivers/net/usb/smsc75xx.c:83 [inline]
> smsc75xx_wait_ready drivers/net/usb/smsc75xx.c:969 [inline]
> smsc75xx_bind+0x44c/0x12d0 drivers/net/usb/smsc75xx.c:1483
> usbnet_probe+0x10d3/0x3950 drivers/net/usb/usbnet.c:1722

Hi,

this looks like a false positive to me.
The offending code is likely this:

if (size) {
buf = kmalloc(size, GFP_KERNEL);
if (!buf)
goto out;
}

err = usb_control_msg(dev->udev, usb_rcvctrlpipe(dev->udev, 0),
cmd, reqtype, value, index, buf, size,
USB_CTRL_GET_TIMEOUT);

which uses 'buf' uninitialized. But it is used for input.
What is happening here?

Regards
Oliver



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