From f025ab9eb73e46f761f469a2bb7c26a159b3e6c9 Mon Sep 17 00:00:00 2001
From: Ian Abbott <abbotti@mev.co.uk>
Date: Thu, 30 Oct 2014 12:42:29 +0000
Subject: [PATCH] staging: comedi: don't allow read() on async command set up
for "write"
If a Comedi asynchronous command has been set up for data transfer in
the "write" direction on the current "read" subdevice (for those
subdevices that support both directions), don't allow the "read" file
operation as that would mess with the data in the comedi data buffer
that is read by the low-level comedi hardware driver.
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Reviewed-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/staging/comedi/comedi_fops.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/drivers/staging/comedi/comedi_fops.c b/drivers/staging/comedi/comedi_fops.c
index b489d9481a69..452121b6a604 100644
--- a/drivers/staging/comedi/comedi_fops.c
+++ b/drivers/staging/comedi/comedi_fops.c
@@ -2210,6 +2210,10 @@ static ssize_t comedi_read(struct file *file, char __user *buf, size_t nbytes,
retval = -EACCES;
goto out;
}
+ if (async->cmd.flags & CMDF_WRITE) {
+ retval = -EINVAL;
+ goto out;
+ }
add_wait_queue(&async->wait_head, &wait);
while (nbytes > 0 && !retval) {
@@ -2249,6 +2253,10 @@ static ssize_t comedi_read(struct file *file, char __user *buf, size_t nbytes,
retval = -EACCES;
break;
}
+ if (async->cmd.flags & CMDF_WRITE) {
+ retval = -EINVAL;
+ break;
+ }
continue;
}
m = copy_to_user(buf, async->prealloc_buf +
--
2.30.9