Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
From:   Nadav Amit <namit@vmware.com>
To:     Arnd Bergmann <arnd@arndb.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>
CC:     Xavier Deguillard <xdeguillard@vmware.com>,
        pv-drivers <pv-drivers@vmware.com>,
        LKML <linux-kernel@vger.kernel.org>,
        Gil Kupfer <gilkup@gmail.com>,
        Oleksandr Natalenko <onatalen@redhat.com>,
        "ldu@redhat.com" <ldu@redhat.com>,
        "stable@vger.kernel.org" <stable@vger.kernel.org>
Subject: Re: [PATCH v3] vmw_balloon: fixing double free when batching mode is
 off
Thread-Topic: [PATCH v3] vmw_balloon: fixing double free when batching mode is
 off
Thread-Index: AQHT2Argu2pZ34klIkGamyuxGjdz+KQZodaAgC4XGICAAtrGAA==
Date:   Thu, 31 May 2018 20:56:52 +0000
Message-ID: <4D5BA2F0-377D-4959-9786-95E195EE2D22@vmware.com>
References: <20180419063856.GA7643@kroah.com>
 <20180419181722.12273-1-namit@vmware.com>
 <162DEB66-373B-4E01-8D64-3CE7BEF47920@vmware.com>
 <7B3793E8-8DD9-4566-9CCB-6D1B0C364754@vmware.com>
In-Reply-To: <7B3793E8-8DD9-4566-9CCB-6D1B0C364754@vmware.com>
Accept-Language: en-US
Content-Language: en-US
received-spf: None (protection.outlook.com: vmware.com does not designate
 permitted sender hosts)
spamdiagnosticoutput: 1:99
spamdiagnosticmetadata: NSPM
Content-Type: text/plain; charset="us-ascii"
Content-ID: <F614B3A79F02014D8639638865050C13@namprd05.prod.outlook.com>
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0
X-MS-Exchange-CrossTenant-Network-Message-Id: 3c2e5fae-7654-400d-fdaa-08d5c7390992
X-MS-Exchange-CrossTenant-originalarrivaltime: 31 May 2018 20:56:52.8863
 (UTC)
X-MS-Exchange-CrossTenant-fromentityheader: Hosted
X-MS-Exchange-CrossTenant-id: b39138ca-3cee-4b4a-a4d6-cd83d9dd62f0
X-MS-Exchange-Transport-CrossTenantHeadersStamped: SN2PR05MB2494
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

Nadav Amit <namit@vmware.com> wrote:

> Nadav Amit <namit@vmware.com> wrote:
>=20
>> Ping. Please consider it for inclusion for rc4.
>>=20
>> Nadav Amit <namit@vmware.com> wrote:
>>=20
>>> From: Gil Kupfer <gilkup@gmail.com>
>>>=20
>>> The balloon.page field is used for two different purposes if batching i=
s
>>> on or off. If batching is on, the field point to the page which is used
>>> to communicate with with the hypervisor. If it is off, balloon.page
>>> points to the page that is about to be (un)locked.
>>>=20
>>> Unfortunately, this dual-purpose of the field introduced a bug: when th=
e
>>> balloon is popped (e.g., when the machine is reset or the balloon drive=
r
>>> is explicitly removed), the balloon driver frees, unconditionally, the
>>> page that is held in balloon.page.  As a result, if batching is
>>> disabled, this leads to double freeing the last page that is sent to th=
e
>>> hypervisor.
>>>=20
>>> The following error occurs during rmmod when kernel checkers are on, an=
d
>>> the balloon is not empty:
>>>=20
>>> [   42.307653] ------------[ cut here ]------------
>>> [   42.307657] Kernel BUG at ffffffffba1e4b28 [verbose debug info unava=
ilable]
>>> [   42.307720] invalid opcode: 0000 [#1] SMP DEBUG_PAGEALLOC
>>> [   42.312512] Modules linked in: vmw_vsock_vmci_transport vsock ppdev =
joydev vmw_balloon(-) input_leds serio_raw vmw_vmci parport_pc shpchp parpo=
rt i2c_piix4 nfit mac_hid autofs4 vmwgfx drm_kms_helper hid_generic syscopy=
area sysfillrect usbhid sysimgblt fb_sys_fops hid ttm mptspi scsi_transport=
_spi ahci mptscsih drm psmouse vmxnet3 libahci mptbase pata_acpi
>>> [   42.312766] CPU: 10 PID: 1527 Comm: rmmod Not tainted 4.12.0+ #5
>>> [   42.312803] Hardware name: VMware, Inc. VMware Virtual Platform/440B=
X Desktop Reference Platform, BIOS 6.00 09/30/2016
>>> [   42.313042] task: ffff9bf9680f8000 task.stack: ffffbfefc1638000
>>> [   42.313290] RIP: 0010:__free_pages+0x38/0x40
>>> [   42.313510] RSP: 0018:ffffbfefc163be98 EFLAGS: 00010246
>>> [   42.313731] RAX: 000000000000003e RBX: ffffffffc02b9720 RCX: 0000000=
000000006
>>> [   42.313972] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff9bf=
97e08e0a0
>>> [   42.314201] RBP: ffffbfefc163be98 R08: 0000000000000000 R09: 0000000=
000000000
>>> [   42.314435] R10: 0000000000000000 R11: 0000000000000000 R12: fffffff=
fc02b97e4
>>> [   42.314505] R13: ffffffffc02b9748 R14: ffffffffc02b9728 R15: 0000000=
000000200
>>> [   42.314550] FS:  00007f3af5fec700(0000) GS:ffff9bf97e080000(0000) kn=
lGS:0000000000000000
>>> [   42.314599] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>> [   42.314635] CR2: 00007f44f6f4ab24 CR3: 00000003a7d12000 CR4: 0000000=
0000006e0
>>> [   42.314864] Call Trace:
>>> [   42.315774]  vmballoon_pop+0x102/0x130 [vmw_balloon]
>>> [   42.315816]  vmballoon_exit+0x42/0xd64 [vmw_balloon]
>>> [   42.315853]  SyS_delete_module+0x1e2/0x250
>>> [   42.315891]  entry_SYSCALL_64_fastpath+0x23/0xc2
>>> [   42.315924] RIP: 0033:0x7f3af5b0e8e7
>>> [   42.315949] RSP: 002b:00007fffe6ce0148 EFLAGS: 00000206 ORIG_RAX: 00=
000000000000b0
>>> [   42.315996] RAX: ffffffffffffffda RBX: 000055be676401e0 RCX: 00007f3=
af5b0e8e7
>>> [   42.316951] RDX: 000000000000000a RSI: 0000000000000800 RDI: 000055b=
e67640248
>>> [   42.317887] RBP: 0000000000000003 R08: 0000000000000000 R09: 1999999=
999999999
>>> [   42.318845] R10: 0000000000000883 R11: 0000000000000206 R12: 00007ff=
fe6cdf130
>>> [   42.319755] R13: 0000000000000000 R14: 0000000000000000 R15: 000055b=
e676401e0
>>> [   42.320606] Code: c0 74 1c f0 ff 4f 1c 74 02 5d c3 85 f6 74 07 e8 0f=
 d8 ff ff 5d c3 31 f6 e8 c6 fb ff ff 5d c3 48 c7 c6 c8 0f c5 ba e8 58 be 02=
 00 <0f> 0b 66 0f 1f 44 00 00 66 66 66 66 90 48 85 ff 75 01 c3 55 48
>>> [   42.323462] RIP: __free_pages+0x38/0x40 RSP: ffffbfefc163be98
>>> [   42.325735] ---[ end trace 872e008e33f81508 ]---
>>>=20
>>> To solve the bug, we eliminate the dual purpose of balloon.page.
>>>=20
>>> Fixes: f220a80f0c2e ("VMware balloon: add batching to the vmw_balloon."=
)
>>> Cc: stable@vger.kernel.org
>>> Reported-by: Oleksandr Natalenko <onatalen@redhat.com>
>>> Signed-off-by: Gil Kupfer <gilkup@gmail.com>
>>> Signed-off-by: Nadav Amit <namit@vmware.com>
>>> Reviewed-by: Xavier Deguillard <xdeguillard@vmware.com>
>>> ---
>>> drivers/misc/vmw_balloon.c | 23 +++++++----------------
>>> 1 file changed, 7 insertions(+), 16 deletions(-)
>>>=20
>>> diff --git a/drivers/misc/vmw_balloon.c b/drivers/misc/vmw_balloon.c
>>> index 9047c0a529b2..efd733472a35 100644
>>> --- a/drivers/misc/vmw_balloon.c
>>> +++ b/drivers/misc/vmw_balloon.c
>>> @@ -576,15 +576,9 @@ static void vmballoon_pop(struct vmballoon *b)
>>> 		}
>>> 	}
>>>=20
>>> -	if (b->batch_page) {
>>> -		vunmap(b->batch_page);
>>> -		b->batch_page =3D NULL;
>>> -	}
>>> -
>>> -	if (b->page) {
>>> -		__free_page(b->page);
>>> -		b->page =3D NULL;
>>> -	}
>>> +	/* Clearing the batch_page unconditionally has no adverse effect */
>>> +	free_page((unsigned long)b->batch_page);
>>> +	b->batch_page =3D NULL;
>>> }
>>>=20
>>> /*
>>> @@ -991,16 +985,13 @@ static const struct vmballoon_ops vmballoon_batch=
ed_ops =3D {
>>>=20
>>> static bool vmballoon_init_batching(struct vmballoon *b)
>>> {
>>> -	b->page =3D alloc_page(VMW_PAGE_ALLOC_NOSLEEP);
>>> -	if (!b->page)
>>> -		return false;
>>> +	struct page *page;
>>>=20
>>> -	b->batch_page =3D vmap(&b->page, 1, VM_MAP, PAGE_KERNEL);
>>> -	if (!b->batch_page) {
>>> -		__free_page(b->page);
>>> +	page =3D alloc_page(GFP_KERNEL | __GFP_ZERO);
>>> +	if (!page)
>>> 		return false;
>>> -	}
>>>=20
>>> +	b->batch_page =3D page_address(page);
>>> 	return true;
>>> }
>>>=20
>>> --=20
>>> 2.14.1
>=20
> Greg, can you please include this patch?? 4.17 is almost out of the door,
> and the last version was sent a month ago.
>=20
> If you have any reservations, please let me know immediately.

Arnd,

Perhaps you can - the very least - respond (or just include the patch)?

The last version of this patch was sent over a month ago.

Thanks,
Nadav=