From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-co1nam03on0118.outbound.protection.outlook.com ([104.47.40.118]:6048 "EHLO NAM03-CO1-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1032119AbeCAP3F (ORCPT ); Thu, 1 Mar 2018 10:29:05 -0500 From: Sasha Levin To: "stable@vger.kernel.org" , "stable-commits@vger.kernel.org" CC: Jiri Slaby , Herbert Xu , Sasha Levin Subject: [added to the 4.1 stable tree] hwrng: core - sleep interruptible in read Date: Thu, 1 Mar 2018 15:24:01 +0000 Message-ID: <20180301152116.1486-148-alexander.levin@microsoft.com> References: <20180301152116.1486-1-alexander.levin@microsoft.com> In-Reply-To: <20180301152116.1486-1-alexander.levin@microsoft.com> Content-Language: en-US Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Sender: stable-owner@vger.kernel.org List-ID: From: Jiri Slaby This patch has been added to the 4.1 stable tree. If you have any objections, please let us know. =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D [ Upstream commit 1ab87298cb59b649d8d648d25dc15b36ab865f5a ] hwrng kthread can be waiting via hwrng_fillfn for some data from a rng like virtio-rng: hwrng D ffff880093e17798 0 382 2 0x00000000 ... Call Trace: [] wait_for_completion_killable+0x96/0x210 [] virtio_read+0x57/0xf0 [virtio_rng] [] hwrng_fillfn+0x75/0x130 [] kthread+0xf3/0x110 And when some user program tries to read the /dev node in this state, we get: rngd D ffff880093e17798 0 762 1 0x00000004 ... Call Trace: [] mutex_lock_nested+0x15c/0x3e0 [] rng_dev_read+0x6e/0x240 [] __vfs_read+0x28/0xe0 [] vfs_read+0x83/0x130 And this is indeed unkillable. So use mutex_lock_interruptible instead of mutex_lock in rng_dev_read and exit immediatelly when interrupted. And possibly return already read data, if any (as POSIX allows). v2: use ERESTARTSYS instead of EINTR Signed-off-by: Jiri Slaby Cc: Matt Mackall Cc: Herbert Xu Cc: Signed-off-by: Herbert Xu Signed-off-by: Sasha Levin --- drivers/char/hw_random/core.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c index 5643b65cee20..0ff7682cfb14 100644 --- a/drivers/char/hw_random/core.c +++ b/drivers/char/hw_random/core.c @@ -238,7 +238,10 @@ static ssize_t rng_dev_read(struct file *filp, char __= user *buf, goto out; } =20 - mutex_lock(&reading_mutex); + if (mutex_lock_interruptible(&reading_mutex)) { + err =3D -ERESTARTSYS; + goto out_put; + } if (!data_avail) { bytes_read =3D rng_get_data(rng, rng_buffer, rng_buffer_size(), @@ -288,6 +291,7 @@ static ssize_t rng_dev_read(struct file *filp, char __u= ser *buf, =20 out_unlock_reading: mutex_unlock(&reading_mutex); +out_put: put_rng(rng); goto out; } --=20 2.14.1