From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7A6DA2FE58F; Mon, 3 Nov 2025 11:00:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762167607; cv=none; b=cXAWPq7dBYMEOwfBemA3whRxiPxHQB0D9Mye0S010xJMVkQ5qZB+eOv8v5HeXtDMvjZK0AfGN/AYoBTv2VhaoSVIiIRRYBdKEAPJm7pnaucPfHSFtbCrZPgtAR3mgF9pdE1fVzn89XDMFgNzLdR8MBOQzWTGv4NkoEuw6JXstj0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762167607; c=relaxed/simple; bh=O3PGyy62CpQtmQKFEa1ztQogpTFwHYoyl2KgzbZ7biM=; h=Message-ID:Date:MIME-Version:From:Subject:To:Cc:References: In-Reply-To:Content-Type; b=u1TnL3cBFUa56guBVsAvraabCyae4qeEFVGUUGRAhZGHEZAv8eCXaotHfUyRCl2714pW2l7gpPcbBRuhVLDg0QhYhYEgWWzg3kb0tQU09r3hkASQqT7NKY0jxOyjPlq1dQZzl1zP0y9bA7PY7AW6dfQfP2Pknq9LN6+6Oxics9c= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=MX6mUw5q; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="MX6mUw5q" Received: by smtp.kernel.org (Postfix) with ESMTPSA id AB343C4CEFD; Mon, 3 Nov 2025 11:00:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1762167607; bh=O3PGyy62CpQtmQKFEa1ztQogpTFwHYoyl2KgzbZ7biM=; h=Date:From:Subject:To:Cc:References:In-Reply-To:From; b=MX6mUw5qB9OHkhzfmKLi2wgalP4ZfRRUKB5Nwk46RjSm6SKWbMxLM8s157Bub2Ksa IIDpCvtCD+78xLDE/gNa83GUOkH9zsjtDlhjyB30roPGiJv3IJ7HxzRiJLor51RRJe E+E9QXo4PlihMlIcnqzAA0GO0wSUN0PFn+1wBtUumxtmB8fQOo/oykrO0nohh/Mo9H n325OFjMKzF2j+WwrPXwLcsSvRGdNI7LzSwrpuH6zX6AHUNQyD0xBrs9E6J5Ew+Q4l GYXgVqBa/iJX0XhOT02IpcpTaQqyanFLiByGHG5F+9FSWmhSS8LulrQvLq+4nwX8+4 c6frT+C4VkCdQ== Message-ID: <24d04c2c-50b1-48ec-8ba9-c09ef29fd3fd@kernel.org> Date: Mon, 3 Nov 2025 12:00:04 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird From: Hans Verkuil Subject: Re: [PATCH V2] media: dvb-usb: Optimizing err() output To: Edward Adam Davis Cc: linux-kernel@vger.kernel.org, linux-media@vger.kernel.org, mchehab@kernel.org, syzbot+480edd2cadb85ddb4bbe@syzkaller.appspotmail.com, syzkaller-bugs@googlegroups.com References: Content-Language: en-US, nl In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 14/10/2025 02:30, Edward Adam Davis wrote: > syzbot reported a uninit-value in pctv452e_i2c_msg. [1] > > When the snd_len or rcv_len check fails and jumps to failed, buf is > uninitialized, triggering the uninit-value issue. > > Setting the err() output buf byte count to 0 before jumping to failed > before initializing buf and setting it to 7 after initializing buf avoids > this warning. > > [1] > BUG: KMSAN: uninit-value in hex_string+0x681/0x740 lib/vsprintf.c:1220 > pctv452e_i2c_msg+0x82a/0x8f0 drivers/media/usb/dvb-usb/pctv452e.c:467 > pctv452e_i2c_xfer+0x2e6/0x4c0 drivers/media/usb/dvb-usb/pctv452e.c:502 > > Reported-by: syzbot+480edd2cadb85ddb4bbe@syzkaller.appspotmail.com > Closes: https://syzkaller.appspot.com/bug?extid=480edd2cadb85ddb4bbe > Signed-off-by: Edward Adam Davis > --- > V1 -> V2: subject typos > > drivers/media/usb/dvb-usb/pctv452e.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/drivers/media/usb/dvb-usb/pctv452e.c b/drivers/media/usb/dvb-usb/pctv452e.c > index 5094de9a312e..3b6e86a8e9ff 100644 > --- a/drivers/media/usb/dvb-usb/pctv452e.c > +++ b/drivers/media/usb/dvb-usb/pctv452e.c > @@ -420,7 +420,7 @@ static int pctv452e_i2c_msg(struct dvb_usb_device *d, u8 addr, > struct pctv452e_state *state = d->priv; > u8 *buf; > u8 id; > - int ret; > + int ret, plen = 0; Adding a plen variable isn't the right fix... > > buf = kmalloc(64, GFP_KERNEL); > if (!buf) > @@ -432,6 +432,7 @@ static int pctv452e_i2c_msg(struct dvb_usb_device *d, u8 addr, > if (snd_len > 64 - 7 || rcv_len > 64 - 7) > goto failed; ...this check should be moved up to before the kmalloc and just return -EINVAL. That also avoids incrementing state->c in that case. Regards, Hans > > + plen = 7; > buf[0] = SYNC_BYTE_OUT; > buf[1] = id; > buf[2] = PCTV_CMD_I2C; > @@ -466,7 +467,7 @@ static int pctv452e_i2c_msg(struct dvb_usb_device *d, u8 addr, > failed: > err("I2C error %d; %02X %02X %02X %02X %02X -> %*ph", > ret, SYNC_BYTE_OUT, id, addr << 1, snd_len, rcv_len, > - 7, buf); > + plen, buf); > > kfree(buf); > return ret;