linux-kernel - [PATCH 3.16 203/346] staging: comedi: ni_mio_common: fix AO inttrig backwards compatibility

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: <lsq.1479082460.672802699@decadent.org.uk>
Date:   Mon, 14 Nov 2016 00:14:20 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Ian Abbott" <abbotti@....co.uk>,
        "Spencer Olson" <olsonse@...ch.edu>,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
        "H Hartley Sweeten" <hsweeten@...ionengravers.com>
Subject: [PATCH 3.16 203/346] staging: comedi: ni_mio_common: fix AO
 inttrig backwards compatibility

3.16.39-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Ian Abbott <abbotti@....co.uk>

commit f0f4b0cc3a8cffd983f5940d46cd0227f3f5710a upstream.

Commit ebb657babfa9 ("staging: comedi: ni_mio_common: clarify the
cmd->start_arg validation and use") introduced a backwards compatibility
issue in the use of asynchronous commands on the AO subdevice when
`start_src` is `TRIG_EXT`.  Valid values for `start_src` are `TRIG_INT`
(for internal, software trigger), and `TRIG_EXT` (for external trigger).
When set to `TRIG_EXT`.  In both cases, the driver relies on an
internal, software trigger to set things up (allowing the user
application to write sufficient samples to the data buffer before the
trigger), so it acts as a software "pre-trigger" in the `TRIG_EXT` case.
The software trigger is handled by `ni_ao_inttrig()`.

Prior to the above change, when `start_src` was `TRIG_INT`, `start_arg`
was required to be 0, and `ni_ao_inttrig()` checked that the software
trigger number was also 0.  After the above change, when `start_src` was
`TRIG_INT`, any value was allowed for `start_arg`, and `ni_ao_inttrig()`
checked that the software trigger number matched this `start_arg` value.
The backwards compatibility issue is that the internal trigger number
now has to match `start_arg` when `start_src` is `TRIG_EXT` when it
previously had to be 0.

Fix the backwards compatibility issue in `ni_ao_inttrig()` by always
allowing software trigger number 0 when `start_src` is something other
than `TRIG_INT`.

Thanks to Spencer Olson for reporting the issue.

Signed-off-by: Ian Abbott <abbotti@....co.uk>
Reported-by: Spencer Olson <olsonse@...ch.edu>
Fixes: ebb657babfa9 ("staging: comedi: ni_mio_common: clarify the cmd->start_arg validation and use")
Reviewed-by: H Hartley Sweeten <hsweeten@...ionengravers.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/staging/comedi/drivers/ni_mio_common.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

--- a/drivers/staging/comedi/drivers/ni_mio_common.c
+++ b/drivers/staging/comedi/drivers/ni_mio_common.c
@@ -2959,7 +2959,15 @@ static int ni_ao_inttrig(struct comedi_d
 	int i;
 	static const int timeout = 1000;

-	if (trig_num != cmd->start_arg)
+	/*
+	 * Require trig_num == cmd->start_arg when cmd->start_src == TRIG_INT.
+	 * For backwards compatibility, also allow trig_num == 0 when
+	 * cmd->start_src != TRIG_INT (i.e. when cmd->start_src == TRIG_EXT);
+	 * in that case, the internal trigger is being used as a pre-trigger
+	 * before the external trigger.
+	 */
+	if (!(trig_num == cmd->start_arg ||
+	      (trig_num == 0 && cmd->start_src != TRIG_INT)))
 		return -EINVAL;

 	/* Null trig at beginning prevent ao start trigger from executing more than