Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Subject: Re: [Linux-kernel-mentees] [PATCH] block/scsi-ioctl: Prevent
 kernel-infoleak in scsi_put_cdrom_generic_arg()
To:     Peilin Ye <yepeilin.cs@gmail.com>
Cc:     Dan Carpenter <dan.carpenter@oracle.com>,
        Arnd Bergmann <arnd@arndb.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-kernel-mentees@lists.linuxfoundation.org,
        linux-block@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20200727161932.322955-1-yepeilin.cs@gmail.com>
From:   Jens Axboe <axboe@kernel.dk>
Message-ID: <78d90a98-7bd5-1604-cc27-90842c365ecf@kernel.dk>
Date:   Mon, 27 Jul 2020 10:25:42 -0600
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101
 Thunderbird/68.10.0
MIME-Version: 1.0
In-Reply-To: <20200727161932.322955-1-yepeilin.cs@gmail.com>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On 7/27/20 10:19 AM, Peilin Ye wrote:
> scsi_put_cdrom_generic_arg() is copying uninitialized stack memory to
> userspace due to the compiler not initializing holes in statically
> allocated structures. Fix it by initializing `cgc32` using memset().

Could also just add the appropriate pad, so the compiler does the
right thing.


diff --git a/block/scsi_ioctl.c b/block/scsi_ioctl.c
index ef722f04f88a..72108404718f 100644
--- a/block/scsi_ioctl.c
+++ b/block/scsi_ioctl.c
@@ -651,6 +651,7 @@ struct compat_cdrom_generic_command {
 	compat_int_t	stat;
 	compat_caddr_t	sense;
 	unsigned char	data_direction;
+	unsigned char	pad[3];
 	compat_int_t	quiet;
 	compat_int_t	timeout;
 	compat_caddr_t	reserved[1];

-- 
Jens Axboe