linux-kernel - [PATCH v2] hw_random: core, sleep interruptible in read

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <1448639443-21760-1-git-send-email-jslaby@suse.cz>
Date:	Fri, 27 Nov 2015 16:50:43 +0100
From:	Jiri Slaby <jslaby@...e.cz>
To:	herbert@...dor.apana.org.au
Cc:	linux-kernel@...r.kernel.org, Jiri Slaby <jslaby@...e.cz>,
	Matt Mackall <mpm@...enic.com>, linux-crypto@...r.kernel.org
Subject: [PATCH v2] hw_random: core, sleep interruptible in read

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:
 [<ffffffff817339c6>] wait_for_completion_killable+0x96/0x210
 [<ffffffffa00aa1b7>] virtio_read+0x57/0xf0 [virtio_rng]
 [<ffffffff814f4a35>] hwrng_fillfn+0x75/0x130
 [<ffffffff810aa243>] 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:
 [<ffffffff817351ac>] mutex_lock_nested+0x15c/0x3e0
 [<ffffffff814f478e>] rng_dev_read+0x6e/0x240
 [<ffffffff81231958>] __vfs_read+0x28/0xe0
 [<ffffffff81232393>] 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 <jslaby@...e.cz>
Cc: Matt Mackall <mpm@...enic.com>
Cc: Herbert Xu <herbert@...dor.apana.org.au>
Cc: <linux-crypto@...r.kernel.org>
---
 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

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/