Re: [PATCH v1 3/6] virtio 9p: Fix an overflow

From: Alexander Shishkin <alexander.shishkin@linux.intel.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: jasowang@redhat.com, virtualization@lists.linux-foundation.org,
	linux-kernel@vger.kernel.org, elena.reshetova@intel.com,
	kirill.shutemov@linux.intel.com, Andi Kleen <ak@linux.intel.com>,
	Christian Schoenebeck <linux_oss@crudebyte.com>,
	Eric Van Hensbergen <ericvh@gmail.com>,
	Latchesar Ionkov <lucho@ionkov.net>,
	Dominique Martinet <asmadeus@codewreck.org>,
	v9fs-developer@lists.sourceforge.net,
	alexander.shishkin@linux.intel.com
Subject: Re: [PATCH v1 3/6] virtio 9p: Fix an overflow
Date: Fri, 20 Jan 2023 18:29:11 +0200	[thread overview]
Message-ID: <871qnpqieg.fsf@ubik.fi.intel.com> (raw)
In-Reply-To: <20230120074817-mutt-send-email-mst@kernel.org>

"Michael S. Tsirkin" <mst@redhat.com> writes:

> On Thu, Jan 19, 2023 at 03:57:18PM +0200, Alexander Shishkin wrote:
>> From: Andi Kleen <ak@linux.intel.com>
>> 
>> diff --git a/net/9p/trans_virtio.c b/net/9p/trans_virtio.c
>> index 3c27ffb781e3..a78e4d80e5ba 100644
>> --- a/net/9p/trans_virtio.c
>> +++ b/net/9p/trans_virtio.c
>> @@ -629,7 +629,7 @@ static int p9_virtio_probe(struct virtio_device *vdev)
>>  		err = -EINVAL;
>>  		goto out_free_vq;
>>  	}
>> -	tag = kzalloc(tag_len + 1, GFP_KERNEL);
>> +	tag = kzalloc((u32)tag_len + 1, GFP_KERNEL);
>>  	if (!tag) {
>>  		err = -ENOMEM;
>>  		goto out_free_vq;
>
> Hmm are you sure there's a difference in behaviour? I thought C will just
> extend the integer to int.

Actually, you're right, integer promotion would extend the original
expression to int. I'll drop this patch also.

Thanks,
--
Alex