[3.5.y.z,extended,stable] Patch "staging: comedi: check s->async for poll(), read() and" has been added to staging queue

Message ID 1361895198-27651-1-git-send-email-luis.henriques@canonical.com
State New
Headers show

Commit Message

Luis Henriques Feb. 26, 2013, 4:13 p.m.
This is a note to let you know that I have just added a patch titled

    staging: comedi: check s->async for poll(), read() and

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:


If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see



From 0755f8d198f7cabf01905e682bf6a665e6787384 Mon Sep 17 00:00:00 2001
From: Ian Abbott <abbotti@mev.co.uk>
Date: Tue, 5 Feb 2013 12:50:40 +0000
Subject: [PATCH] staging: comedi: check s->async for poll(), read() and

commit cc400e185c07c15a42d2635995f422de5b94b696 upstream.

Some low-level comedi drivers (incorrectly) point `dev->read_subdev` or
`dev->write_subdev` to a subdevice that does not support asynchronous
commands.  Comedi's poll(), read() and write() file operation handlers
assume these subdevices do support asynchronous commands.  In
particular, they assume `s->async` is valid (where `s` points to the
read or write subdevice), which it won't be if it has been set
incorrectly.  This can lead to a NULL pointer dereference.

Check `s->async` is non-NULL in `comedi_poll()`, `comedi_read()` and
`comedi_write()` to avoid the bug.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[ luis: adjust context, variables names ]
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
 drivers/staging/comedi/comedi_fops.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)



diff --git a/drivers/staging/comedi/comedi_fops.c b/drivers/staging/comedi/comedi_fops.c
index 2831080..b08cbbe 100644
--- a/drivers/staging/comedi/comedi_fops.c
+++ b/drivers/staging/comedi/comedi_fops.c
@@ -1866,7 +1866,7 @@  static unsigned int comedi_poll(struct file *file, poll_table *wait)

 	mask = 0;
 	read_subdev = comedi_get_read_subdevice(dev_file_info);
-	if (read_subdev) {
+	if (read_subdev && read_subdev->async) {
 		poll_wait(file, &read_subdev->async->wait_head, wait);
 		if (!read_subdev->busy
 		    || comedi_buf_read_n_available(read_subdev->async) > 0
@@ -1876,7 +1876,7 @@  static unsigned int comedi_poll(struct file *file, poll_table *wait)
 	write_subdev = comedi_get_write_subdevice(dev_file_info);
-	if (write_subdev) {
+	if (write_subdev && write_subdev->async) {
 		poll_wait(file, &write_subdev->async->wait_head, wait);
@@ -1918,7 +1918,7 @@  static ssize_t comedi_write(struct file *file, const char __user *buf,

 	s = comedi_get_write_subdevice(dev_file_info);
-	if (s == NULL) {
+	if (!s || !s->async) {
 		retval = -EIO;
 		goto done;
@@ -2029,7 +2029,7 @@  static ssize_t comedi_read(struct file *file, char __user *buf, size_t nbytes,

 	s = comedi_get_read_subdevice(dev_file_info);
-	if (s == NULL) {
+	if (!s || !s->async) {
 		retval = -EIO;
 		goto done;