Date:   Thu, 9 Feb 2023 16:12:23 +0100
From:   Jiri Pirko <jiri@resnulli.us>
To:     Miko Larsson <mikoxyzzz@gmail.com>
Cc:     "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>, linux-usb@vger.kernel.org,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
        Greg KH <gregkh@linuxfoundation.org>
Subject: Re: [PATCH v2] net/usb: kalmia: Fix uninit-value in
 kalmia_send_init_packet
Message-ID: <Y+UNV9xp/U+56Tlx@nanopsycho>
References: <7266fe67c835f90e5c257129014a63e79e849ef9.camel@gmail.com>
 <f0b62f38c042d2dcb8b8e83c827d76db2ac5d7ad.camel@gmail.com>
 <Y9pY61y1nwTuzMOa@nanopsycho>
 <23e899f83c4f05a18deb2f86047d57d941205374.camel@gmail.com>
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Precedence: bulk

Thu, Feb 09, 2023 at 03:47:12PM CET, mikoxyzzz@gmail.com wrote:
>On Wed, 2023-02-01 at 13:19 +0100, Jiri Pirko wrote:
>> Tue, Jan 31, 2023 at 03:20:33PM CET, mikoxyzzz@gmail.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@syzkaller.appspotmail.com
>> > Signed-off-by: Miko Larsson <mikoxyzzz@gmail.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.
>
>Something like this, then?

Yes.

>
>diff --git a/drivers/net/usb/kalmia.c b/drivers/net/usb/kalmia.c
>index 9f2b70ef39aa..613fc6910f14 100644
>--- a/drivers/net/usb/kalmia.c
>+++ b/drivers/net/usb/kalmia.c
>@@ -65,8 +65,8 @@ kalmia_send_init_packet(struct usbnet *dev, u8 *init_msg, u8 init_msg_len,
> 		init_msg, init_msg_len, &act_len, KALMIA_USB_TIMEOUT);
> 	if (status != 0) {
> 		netdev_err(dev->net,
>-			"Error sending init packet. Status %i, length %i\n",
>-			status, act_len);
>+			"Error sending init packet. Status %i\n",
>+			status);
> 		return status;
> 	}
> 	else if (act_len != init_msg_len) {
>@@ -83,8 +83,8 @@ kalmia_send_init_packet(struct usbnet *dev, u8 *init_msg, u8 init_msg_len,
> 
> 	if (status != 0)
> 		netdev_err(dev->net,
>-			"Error receiving init result. Status %i, length %i\n",
>-			status, act_len);
>+			"Error receiving init result. Status %i\n",
>+			status);
> 	else if (act_len != expected_len)
> 		netdev_err(dev->net, "Unexpected init result length: %i\n",
> 			act_len);
>
>-- 
>~miko