linux-kernel - Re: [PATCH RESEND] scsi: sg: Prevent potential double frees in sg driver

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Date:   Mon, 01 Oct 2018 10:20:37 -0700
From:   Bart Van Assche <bvanassche@....org>
To:     Nick Desaulniers <ndesaulniers@...gle.com>, hch@...radead.org
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, LKML <linux-kernel@...r.kernel.org>,
        Robb Glasser <rglasser@...gle.com>, evgreen@...omium.org,
        stable@...r.kernel.org
Subject: Re: [PATCH RESEND] scsi: sg: Prevent potential double frees in sg
 driver

On Mon, 2018-10-01 at 10:12 -0700, Nick Desaulniers wrote:
> On Mon, Oct 1, 2018 at 9:16 AM Evan Green <evgreen@...omium.org> wrote:
> > 
> > From: Robb Glasser <rglasser@...gle.com>
> > 
> > sg_ioctl could be spammed by requests, leading to a double free in
> > __free_pages. This protects the entry points of sg_ioctl where the
> > memory could be corrupted by a double call to __free_pages if multiple
> > requests are happening concurrently.
> > 
> > Signed-off-by: Robb Glasser <rglasser@...gle.com>
> > Signed-off-by: Nick Desaulniers <ndesaulniers@...gle.com>
> > Signed-off-by: Evan Green <evgreen@...omium.org>
> > Cc: stable@...r.kernel.org
> > 
> > ---
> > Reposting this patch from last summer, as it looks like it fell in between
> > the cracks.
> 
> Christoph, do you still feel strongly about: https://lkml.org/lkml/2017/8/5/75 ?

I don't know how Christoph feels about it, but serializing all SG I/O seems
like a regression to me. If one sg command hangs I usually try to send
another sg command to the same SCSI device from another shell to get more
information about the nature of the hang. Serializing all SG I/O would make
that impossible.

Bart.