From: Luca Fancellu <luca.fancellu@arm.com>
To: Juergen Gross <jgross@suse.com>
Cc: xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org,
"Boris Ostrovsky" <boris.ostrovsky@oracle.com>,
"Stefano Stabellini" <sstabellini@kernel.org>,
stable@vger.kernel.org,
"Marek Marczykowski-Górecki" <marmarek@invisiblethingslab.com>
Subject: Re: [PATCH] xen/gntdev: fix gntdev_mmap() error exit path
Date: Fri, 23 Apr 2021 07:55:38 +0100 [thread overview]
Message-ID: <467B8109-C829-4755-8398-196E50090898@arm.com> (raw)
In-Reply-To: <20210423054038.26696-1-jgross@suse.com>
> On 23 Apr 2021, at 06:40, Juergen Gross <jgross@suse.com> wrote:
>
> Commit d3eeb1d77c5d0af ("xen/gntdev: use mmu_interval_notifier_insert")
> introduced an error in gntdev_mmap(): in case the call of
> mmu_interval_notifier_insert_locked() fails the exit path should not
> call mmu_interval_notifier_remove(), as this might result in NULL
> dereferences.
>
> One reason for failure is e.g. a signal pending for the running
> process.
>
> Fixes: d3eeb1d77c5d0af ("xen/gntdev: use mmu_interval_notifier_insert")
> Cc: stable@vger.kernel.org
> Reported-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
> Tested-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
> Signed-off-by: Juergen Gross <jgross@suse.com>
> ---
> drivers/xen/gntdev.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
> index f01d58c7a042..a3e7be96527d 100644
> --- a/drivers/xen/gntdev.c
> +++ b/drivers/xen/gntdev.c
> @@ -1017,8 +1017,10 @@ static int gntdev_mmap(struct file *flip, struct vm_area_struct *vma)
> err = mmu_interval_notifier_insert_locked(
> &map->notifier, vma->vm_mm, vma->vm_start,
> vma->vm_end - vma->vm_start, &gntdev_mmu_ops);
> - if (err)
> + if (err) {
> + map->vma = NULL;
> goto out_unlock_put;
> + }
> }
> mutex_unlock(&priv->lock);
>
> --
> 2.26.2
>
>
Hi Juergen,
I can see from the code that there is another path to out_unlock_put label some lines before:
[…]
vma->vm_private_data = map;
if (map->flags) {
if ((vma->vm_flags & VM_WRITE) &&
(map->flags & GNTMAP_readonly))
goto out_unlock_put;
} else {
map->flags = GNTMAP_host_map;
if (!(vma->vm_flags & VM_WRITE))
map->flags |= GNTMAP_readonly;
}
[…]
Can be the case that use_ptemod is != 0 also for that path?
Cheers,
Luca
next prev parent reply other threads:[~2021-04-23 6:56 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-23 5:40 [PATCH] xen/gntdev: fix gntdev_mmap() error exit path Juergen Gross
2021-04-23 6:55 ` Luca Fancellu [this message]
2021-04-23 7:00 ` Juergen Gross
2021-04-23 7:04 ` Luca Fancellu
2021-05-08 0:41 ` Marek Marczykowski-Górecki
2021-05-10 9:26 ` Juergen Gross
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