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:   Sasha Levin <Alexander.Levin@microsoft.com>
To:     "stable@vger.kernel.org" <stable@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
CC:     Goran Ferenc <goran.ferenc@imgtec.com>,
        Miodrag Dinic <miodrag.dinic@imgtec.com>,
        Aleksandar Markovic <aleksandar.markovic@imgtec.com>,
        Douglas Leung <douglas.leung@imgtec.com>,
        James Hogan <james.hogan@imgtec.com>,
        Paul Burton <paul.burton@imgtec.com>,
        Petar Jovanovic <petar.jovanovic@imgtec.com>,
        Raghu Gandham <raghu.gandham@imgtec.com>,
        "linux-mips@linux-mips.org" <linux-mips@linux-mips.org>,
        Ralf Baechle <ralf@linux-mips.org>,
        Sasha Levin <Alexander.Levin@microsoft.com>
Subject: [PATCH AUTOSEL for 4.9 170/293] MIPS: VDSO: Fix conversions in
 do_monotonic()/do_monotonic_coarse()
Thread-Topic: [PATCH AUTOSEL for 4.9 170/293] MIPS: VDSO: Fix conversions in
 do_monotonic()/do_monotonic_coarse()
Thread-Index: AQHTz5k2g3dlmx/obkGf4P3vgVx6iA==
Date:   Mon, 9 Apr 2018 00:25:07 +0000
Message-ID: <20180409002239.163177-170-alexander.levin@microsoft.com>
References: <20180409002239.163177-1-alexander.levin@microsoft.com>
In-Reply-To: <20180409002239.163177-1-alexander.levin@microsoft.com>
Accept-Language: en-US
Content-Language: en-US
received-spf: None (protection.outlook.com: microsoft.com does not designate
 permitted sender hosts)
spamdiagnosticoutput: 1:99
spamdiagnosticmetadata: NSPM
Content-Type: text/plain; charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0
X-MS-Exchange-CrossTenant-Network-Message-Id: bdc530d9-5ce0-429f-640c-08d59db135d9
X-MS-Exchange-CrossTenant-originalarrivaltime: 09 Apr 2018 00:25:07.6126
 (UTC)
X-MS-Exchange-CrossTenant-fromentityheader: Hosted
X-MS-Exchange-CrossTenant-id: 72f988bf-86f1-41af-91ab-2d7cd011db47
X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM5PR2101MB0917
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

From: Goran Ferenc <goran.ferenc@imgtec.com>

[ Upstream commit 8ec7f15b8cca4f790df5cdf33f26e2926d4ee2fd ]

Fix incorrect calculation in do_monotonic() and do_monotonic_coarse()
function that in turn caused incorrect values returned by the vdso
version of system call clock_gettime() on mips64 if its system clock
ID parameter was CLOCK_MONOTONIC or CLOCK_MONOTONIC_COARSE.

Consider these variables and their types on mips32 and mips64:

tk->wall_to_monotonic.tv_sec  s64, s64   (kernel/vdso.c)
vdso_data.wall_to_mono_sec    u32, u32   (kernel/vdso.c)
to_mono_sec                   u32, u32   (vdso/gettimeofday.c)
ts->tv_sec                    s32, s64   (vdso/gettimeofday.c)

For mips64 case, u32 vdso_data.wall_to_mono_sec variable is updated
from the 64-bit signed variable tk->wall_to_monotonic.tv_sec
(kernel/vdso.c:76) which is a negative number holding the time passed
from 1970-01-01 to the time boot started. This 64-bit signed value is
currently around 47+ years, in seconds. For instance, let this value
be:

-1489757461

or

11111111111111111111111111111111 10100111001101000001101011101011

By updating 32-bit vdso_data.wall_to_mono_sec variable, we lose upper
32 bits (signed 1's).

to_mono_sec variable is a parameter of do_monotonic() and
do_monotonic_coarse() functions which holds vdso_data.wall_to_mono_sec
value. Its value needs to be added (or subtracted considering it holds
negative value from the tk->wall_to_monotonic.tv_sec) to the current
time passed from 1970-01-01 (ts->tv_sec), which is again something like
47+ years, but increased by the time passed from the boot to the
current time. ts->tv_sec is 32-bit long in case of 32-bit architecture
and 64-bit long in case of 64-bit architecture. Consider the update of
ts->tv_sec (vdso/gettimeofday.c:55 & 167):

ts->tv_sec +=3D to_mono_sec;

mips32 case: This update will be performed correctly, since both
ts->tv_sec and to_mono_sec are 32-bit long and the sign in to_mono_sec
is preserved. Implicit conversion from u32 to s32 will be done
correctly.

mips64 case: This update will be wrong, since the implicit conversion
will not be done correctly. The reason is that the conversion will be
from u32 to s64. This is because to_mono_sec is 32-bit long for both
mips32 and mips64 cases and s64..33 bits of converted to_mono_sec
variable will be zeros.

So, in order to make MIPS64 implementation work properly for
MONOTONIC and MONOTONIC_COARSE clock ids on mips64, the size of
wall_to_mono_sec variable in mips_vdso_data union and respective
parameters in do_monotonic() and do_monotonic_coarse() functions
should be changed from u32 to u64. Because of consistency, this
size change from u32 and u64 is also done for wall_to_mono_nsec
variable and corresponding function parameters.

As far as similar situations for other architectures are concerned,
let's take a look at arm. Arm has two distinct vdso_data structures
for 32-bit & 64-bit cases, and arm's wall_to_mono_sec and
wall_to_mono_nsec are u32 for 32-bit and u64 for 64-bit cases.
On the other hand, MIPS has only one structure (mips_vdso_data),
hence the need for changing the size of above mentioned parameters.

Signed-off-by: Goran Ferenc <goran.ferenc@imgtec.com>
Signed-off-by: Miodrag Dinic <miodrag.dinic@imgtec.com>
Signed-off-by: Aleksandar Markovic <aleksandar.markovic@imgtec.com>
Cc: Douglas Leung <douglas.leung@imgtec.com>
Cc: James Hogan <james.hogan@imgtec.com>
Cc: Paul Burton <paul.burton@imgtec.com>
Cc: Petar Jovanovic <petar.jovanovic@imgtec.com>
Cc: Raghu Gandham <raghu.gandham@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/16638/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
---
 arch/mips/include/asm/vdso.h  | 4 ++--
 arch/mips/vdso/gettimeofday.c | 8 ++++----
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/arch/mips/include/asm/vdso.h b/arch/mips/include/asm/vdso.h
index 8f4ca5dd992b..b7cd6cf77b83 100644
--- a/arch/mips/include/asm/vdso.h
+++ b/arch/mips/include/asm/vdso.h
@@ -79,8 +79,8 @@ union mips_vdso_data {
 	struct {
 		u64 xtime_sec;
 		u64 xtime_nsec;
-		u32 wall_to_mono_sec;
-		u32 wall_to_mono_nsec;
+		u64 wall_to_mono_sec;
+		u64 wall_to_mono_nsec;
 		u32 seq_count;
 		u32 cs_shift;
 		u8 clock_mode;
diff --git a/arch/mips/vdso/gettimeofday.c b/arch/mips/vdso/gettimeofday.c
index ce89c9e294f9..fd7d433970bf 100644
--- a/arch/mips/vdso/gettimeofday.c
+++ b/arch/mips/vdso/gettimeofday.c
@@ -39,8 +39,8 @@ static __always_inline int do_monotonic_coarse(struct tim=
espec *ts,
 					       const union mips_vdso_data *data)
 {
 	u32 start_seq;
-	u32 to_mono_sec;
-	u32 to_mono_nsec;
+	u64 to_mono_sec;
+	u64 to_mono_nsec;
=20
 	do {
 		start_seq =3D vdso_data_read_begin(data);
@@ -148,8 +148,8 @@ static __always_inline int do_monotonic(struct timespec=
 *ts,
 {
 	u32 start_seq;
 	u64 ns;
-	u32 to_mono_sec;
-	u32 to_mono_nsec;
+	u64 to_mono_sec;
+	u64 to_mono_nsec;
=20
 	do {
 		start_seq =3D vdso_data_read_begin(data);
--=20
2.15.1