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Fri, 23 Apr 2021 06:55:48 +0000 Content-Type: text/plain; charset=utf-8 Subject: Re: [PATCH] xen/gntdev: fix gntdev_mmap() error exit path From: Luca Fancellu In-Reply-To: <20210423054038.26696-1-jgross@suse.com> Date: Fri, 23 Apr 2021 07:55:38 +0100 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?= Content-Transfer-Encoding: quoted-printable Message-Id: <467B8109-C829-4755-8398-196E50090898@arm.com> References: <20210423054038.26696-1-jgross@suse.com> To: Juergen Gross X-Mailer: Apple Mail (2.3654.60.0.2.21) X-Originating-IP: [82.8.129.65] X-ClientProxiedBy: LO4P123CA0500.GBRP123.PROD.OUTLOOK.COM (2603:10a6:600:1ab::19) To VI1PR08MB3629.eurprd08.prod.outlook.com (2603:10a6:803:7f::25) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from a75445.arm.com (82.8.129.65) by LO4P123CA0500.GBRP123.PROD.OUTLOOK.COM (2603:10a6:600:1ab::19) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4042.21 via Frontend Transport; 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X-OriginatorOrg: arm.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 23 Apr 2021 06:55:57.1529 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 0ca6b551-6473-461a-90bf-08d90624d892 X-MS-Exchange-CrossTenant-Id: f34e5979-57d9-4aaa-ad4d-b122a662184d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=f34e5979-57d9-4aaa-ad4d-b122a662184d;Ip=[63.35.35.123];Helo=[64aa7808-outbound-1.mta.getcheckrecipient.com] X-MS-Exchange-CrossTenant-AuthSource: DB5EUR03FT054.eop-EUR03.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: AM0PR08MB4563 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > On 23 Apr 2021, at 06:40, Juergen Gross wrote: >=20 > 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. >=20 > One reason for failure is e.g. a signal pending for the running > process. >=20 > 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(-) >=20 > 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 v= m_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 > --=20 > 2.26.2 >=20 >=20 Hi Juergen, I can see from the code that there is another path to out_unlock_put label = some lines before: [=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] Can be the case that use_ptemod is !=3D 0 also for that path? Cheers, Luca=