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

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Date:   Mon, 1 Oct 2018 10:12:32 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     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, 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 ?

>
>  drivers/scsi/sg.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
> index 8a254bb46a9b..25579d8a16b5 100644
> --- a/drivers/scsi/sg.c
> +++ b/drivers/scsi/sg.c
> @@ -924,8 +924,10 @@ sg_ioctl(struct file *filp, unsigned int cmd_in, unsigned long arg)
>                         return -ENXIO;
>                 if (!access_ok(VERIFY_WRITE, p, SZ_SG_IO_HDR))
>                         return -EFAULT;
> +               mutex_lock(&sfp->parentdp->open_rel_lock);
>                 result = sg_new_write(sfp, filp, p, SZ_SG_IO_HDR,
>                                  1, read_only, 1, &srp);
> +               mutex_unlock(&sfp->parentdp->open_rel_lock);
>                 if (result < 0)
>                         return result;
>                 result = wait_event_interruptible(sfp->read_wait,
> --
> 2.19.0.605.g01d371f741-goog
>


-- 
Thanks,
~Nick Desaulniers