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a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1619161227; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=3gXh3FGsXDlt+Rrt1Wsm/dUEJBcFCjrIm4/In1CZTGc=; b=CoTXtgLIjUHnzL1b7CsMnguagAfqih5iEU0WTUeGVW4ZdrlP5n2grb8OAsdeN3MRxSnaVw Uk5ukFz45myh2gUxahLgpj8Kio8qwESo+5N57AO0r/zZe62zKhYF4vxWPI+1CCJxREIyst 4YFdxBNteM7HJf1hKZzoLgVT9pfbV/g= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 6CAD5AFE2; Fri, 23 Apr 2021 07:00:27 +0000 (UTC) Subject: Re: [PATCH] xen/gntdev: fix gntdev_mmap() error exit path To: Luca Fancellu Cc: xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org, Boris Ostrovsky , Stefano Stabellini , stable@vger.kernel.org, =?UTF-8?Q?Marek_Marczykowski-G=c3=b3recki?= References: <20210423054038.26696-1-jgross@suse.com> <467B8109-C829-4755-8398-196E50090898@arm.com> From: Juergen Gross Message-ID: <9cb9bd6c-8185-9741-31b9-8f6baf3848a3@suse.com> Date: Fri, 23 Apr 2021 09:00:26 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.0 MIME-Version: 1.0 In-Reply-To: <467B8109-C829-4755-8398-196E50090898@arm.com> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="7ayNSUCrXn5ckIGGaFScYNp0p0tZKBGXJ" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --7ayNSUCrXn5ckIGGaFScYNp0p0tZKBGXJ Content-Type: multipart/mixed; boundary="LKCNSGiy0nLMI7qsYI7xNT6BUHoXvzqvv"; protected-headers="v1" From: Juergen Gross To: Luca Fancellu Cc: xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org, Boris Ostrovsky , Stefano Stabellini , stable@vger.kernel.org, =?UTF-8?Q?Marek_Marczykowski-G=c3=b3recki?= Message-ID: <9cb9bd6c-8185-9741-31b9-8f6baf3848a3@suse.com> Subject: Re: [PATCH] xen/gntdev: fix gntdev_mmap() error exit path References: <20210423054038.26696-1-jgross@suse.com> <467B8109-C829-4755-8398-196E50090898@arm.com> In-Reply-To: <467B8109-C829-4755-8398-196E50090898@arm.com> --LKCNSGiy0nLMI7qsYI7xNT6BUHoXvzqvv Content-Type: multipart/mixed; boundary="------------B36DB28A3BBCE5553396DB97" Content-Language: en-US This is a multi-part message in MIME format. --------------B36DB28A3BBCE5553396DB97 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: quoted-printable On 23.04.21 08:55, Luca Fancellu wrote: >=20 >=20 >> On 23 Apr 2021, at 06:40, Juergen Gross 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-G=C3=B3recki >> Tested-by: Marek Marczykowski-G=C3=B3recki >> Signed-off-by: Juergen Gross >> --- >> 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, struc= t vm_area_struct *vma) >> err =3D 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 =3D NULL; >> goto out_unlock_put; >> + } >> } >> mutex_unlock(&priv->lock); >> >> --=20 >> 2.26.2 >> >> >=20 > Hi Juergen, >=20 > I can see from the code that there is another path to out_unlock_put la= bel some lines before: >=20 > [=E2=80=A6] > vma->vm_private_data =3D map; > if (map->flags) { > if ((vma->vm_flags & VM_WRITE) && > (map->flags & GNTMAP_readonly)) > goto out_unlock_put; > } else { > map->flags =3D GNTMAP_host_map; > if (!(vma->vm_flags & VM_WRITE)) > map->flags |=3D GNTMAP_readonly; > } > [=E2=80=A6] >=20 > Can be the case that use_ptemod is !=3D 0 also for that path? map->vma will be NULL in this case, so there will be no problem resulting from that path. 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