linux-kernel - Re: [PATCH v2] scsi: 3w-9xxx: fix a missing-check bug

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Message-ID: <yq1muxaww19.fsf@oracle.com>
Date:   Tue, 08 May 2018 01:34:10 -0400
From:   "Martin K. Petersen" <martin.petersen@...cle.com>
To:     Wenwen Wang <wang6495@....edu>
Cc:     Kangjie Lu <kjlu@....edu>, Adam Radford <aradford@...il.com>,
        "James E.J. Bottomley" <jejb@...ux.vnet.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        linux-scsi@...r.kernel.org,
        linux-kernel@...r.kernel.org (open list)
Subject: Re: [PATCH v2] scsi: 3w-9xxx: fix a missing-check bug


Wenwen,

> In twa_chrdev_ioctl(), the ioctl driver command is firstly copied from the
> userspace pointer 'argp' and saved to the kernel object 'driver_command'.
> Then a security check is performed on the data buffer size indicated by
> 'driver_command', which is 'driver_command.buffer_length'. If the security
> check is passed, the entire ioctl command is copied again from the 'argp'
> pointer and saved to the kernel object 'tw_ioctl'. Then, various operations
> are performed on 'tw_ioctl' according to the 'cmd'. Given that the 'argp'
> pointer resides in userspace, a malicious userspace process can race to
> change the buffer size between the two copies. This way, the user can
> bypass the security check and inject invalid data buffer size. This can
> cause potential security issues in the following execution.
>
> This patch checks for capable(CAP_SYS_ADMIN) in twa_chrdev_open()t o avoid
> the above issues.

Applied patch 1 + 2 to 4.18/scsi-queue. Thank you.

-- 
Martin K. Petersen	Oracle Linux Engineering