linux-kernel - Re: [PATCH v3] sg: mitigate read/write abuse

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Message-ID: <yq1bmbx321v.fsf@oracle.com>
Date:   Tue, 26 Jun 2018 13:11:56 -0400
From:   "Martin K. Petersen" <martin.petersen@...cle.com>
To:     Jann Horn <jannh@...gle.com>
Cc:     Doug Gilbert <dgilbert@...erlog.com>,
        "James E.J. Bottomley" <jejb@...ux.vnet.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        linux-scsi@...r.kernel.org, Christoph Hellwig <hch@...radead.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Andy Lutomirski <luto@...nel.org>,
        linux-kernel@...r.kernel.org, Jens Axboe <axboe@...nel.dk>,
        FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>,
        kernel-hardening@...ts.openwall.com, security@...nel.org,
        Benjamin Block <bblock@...ux.vnet.ibm.com>
Subject: Re: [PATCH v3] sg: mitigate read/write abuse


Jann,

> As Al Viro noted in commit 128394eff343 ("sg_write()/bsg_write() is
> not fit to be called under KERNEL_DS"), sg improperly accesses
> userspace memory outside the provided buffer, permitting kernel memory
> corruption via splice().  But it doesn't just do it on ->write(), also
> on ->read().
>
> As a band-aid, make sure that the ->read() and ->write() handlers can
> not be called in weird contexts (kernel context or credentials
> different from file opener), like for ib_safe_file_access().

Applied to 4.18/scsi-fixes with the naming fix pointed out by Doug.

Thanks!

-- 
Martin K. Petersen	Oracle Linux Engineering