linux-kernel - Re: [Linux-kernel-mentees] [PATCH] block/scsi-ioctl: Prevent kernel-infoleak in scsi_put_cdrom_generic

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Message-ID: <78d90a98-7bd5-1604-cc27-90842c365ecf@kernel.dk>
Date:   Mon, 27 Jul 2020 10:25:42 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     Peilin Ye <yepeilin.cs@...il.com>
Cc:     Dan Carpenter <dan.carpenter@...cle.com>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [Linux-kernel-mentees] [PATCH] block/scsi-ioctl: Prevent
 kernel-infoleak in scsi_put_cdrom_generic_arg()

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