linux-kernel - Re: [PATCH v3] scsi: require CAP_SYS_ADMIN to write to procfs interface

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Date:   Sun, 5 Nov 2017 15:02:10 +1100
From:   Aleksa Sarai <asarai@...e.de>
To:     "James E.J. Bottomley" <jejb@...ux.vnet.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>
Cc:     linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
        containers@...ts.linux-foundation.org,
        Valentin Rothberg <vrothberg@...e.com>, cyphar@...har.com,
        stable@...r.kernel.org, "Eric W. Biederman" <ebiederm@...ssion.com>
Subject: Re: [PATCH v3] scsi: require CAP_SYS_ADMIN to write to procfs
 interface

On 11/05/2017 01:56 PM, Aleksa Sarai wrote:
> Previously, the only capability effectively required to operate on the
> /proc/scsi interface was CAP_DAC_OVERRIDE (or for some other files,
> having an fsuid of GLOBAL_ROOT_UID was enough). This means that
> semi-privileged processes could interfere with core components of a
> system (such as causing a DoS by removing the underlying SCSI device of
> the host's / mount).

An alternative to this patch would be to make the open(2) call fail, if 
you try to open it write-only or read-write. Not sure which would be 
preferred (should it be possible to pass /proc/scsi/scsi to a 
semi-privileged process to write to?).

-- 
Aleksa Sarai
Senior Software Engineer (Containers)
SUSE Linux GmbH
https://www.cyphar.com/