linux-kernel - Re: [PATCH v2] net/usb: kalmia: Fix uninit-value in kalmia_send_init

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Date:   Wed, 1 Feb 2023 13:19:55 +0100
From:   Jiri Pirko <jiri@...nulli.us>
To:     Miko Larsson <mikoxyzzz@...il.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, linux-usb@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Greg KH <gregkh@...uxfoundation.org>
Subject: Re: [PATCH v2] net/usb: kalmia: Fix uninit-value in
 kalmia_send_init_packet

Tue, Jan 31, 2023 at 03:20:33PM CET, mikoxyzzz@...il.com wrote:
>syzbot reports that act_len in kalmia_send_init_packet() is
>uninitialized. Fix this by initializing it to 0.
>
>Fixes: d40261236e8e ("net/usb: Add Samsung Kalmia driver for Samsung GT-B3730")
>Reported-and-tested-by: syzbot+cd80c5ef5121bfe85b55@...kaller.appspotmail.com
>Signed-off-by: Miko Larsson <mikoxyzzz@...il.com>
>---
>v1 -> v2
>* Minor alteration of commit message.
>* Added 'reported-and-tested-by' which is attributed to syzbot.
>
> drivers/net/usb/kalmia.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
>diff --git a/drivers/net/usb/kalmia.c b/drivers/net/usb/kalmia.c
>index 9f2b70ef39aa..b158fb7bf66a 100644
>--- a/drivers/net/usb/kalmia.c
>+++ b/drivers/net/usb/kalmia.c
>@@ -56,7 +56,7 @@ static int
> kalmia_send_init_packet(struct usbnet *dev, u8 *init_msg, u8 init_msg_len,
> 	u8 *buffer, u8 expected_len)
> {
>-	int act_len;
>+	int act_len = 0;
> 	int status;
> 
> 	netdev_dbg(dev->net, "Sending init packet");

Hmm, this is not the right fix.

If the second call of usb_bulk_msg() in this function returns != 0, the
act_len printed out contains the value from previous usb_bulk_msg() call,
which does not make sense.

Printing act_len on error path is pointless, so rather remove it from
the error message entirely for both usb_bulk_msg() calls.