From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754905AbbK0Puv (ORCPT ); Fri, 27 Nov 2015 10:50:51 -0500 Received: from mx2.suse.de ([195.135.220.15]:40857 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751484AbbK0Pur (ORCPT ); Fri, 27 Nov 2015 10:50:47 -0500 From: Jiri Slaby To: herbert@gondor.apana.org.au Cc: linux-kernel@vger.kernel.org, Jiri Slaby , Matt Mackall , linux-crypto@vger.kernel.org Subject: [PATCH v2] hw_random: core, sleep interruptible in read Date: Fri, 27 Nov 2015 16:50:43 +0100 Message-Id: <1448639443-21760-1-git-send-email-jslaby@suse.cz> X-Mailer: git-send-email 2.6.3 In-Reply-To: <20151127130603.GA29503@gondor.apana.org.au> References: <20151127130603.GA29503@gondor.apana.org.au> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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: --- 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 a064237ff362..ca5a5325eb6f 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; } - mutex_lock(&reading_mutex); + if (mutex_lock_interruptible(&reading_mutex)) { + err = -ERESTARTSYS; + goto out_put; + } if (!data_avail) { bytes_read = rng_get_data(rng, rng_buffer, rng_buffer_size(), @@ -288,6 +291,7 @@ out: out_unlock_reading: mutex_unlock(&reading_mutex); +out_put: put_rng(rng); goto out; } -- 2.6.3