patch "iio: backend: fix uninitialized data in debugfs" added to char-misc-next

patch "iio: backend: fix uninitialized data in debugfs" added to char-misc-next

[gregkh]

This is a note to let you know that I've just added the patch titled

    iio: backend: fix uninitialized data in debugfs

to my char-misc git tree which can be found at
    git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc.git
in the char-misc-next branch.

The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)

The patch will also be merged in the next major kernel release
during the merge window.

If you have any questions about this process, please let me know.


From a6e8b14a4897d0b6df9744f33d0a30e6b92368eb Mon Sep 17 00:00:00 2001
From: Dan Carpenter <error27@gmail.com>
Date: Mon, 25 May 2026 10:16:11 +0300
Subject: iio: backend: fix uninitialized data in debugfs

If the *ppos value is non-zero then simple_write_to_buffer() will not
initialize the start of the buf[] buffer.  Non-zero ppos values aren't
going to work at all.  Check for that at the start of the function and
return -ENOSPC.

Fixes: cdf01e0809a4 ("iio: backend: add debugFs interface")
Signed-off-by: Dan Carpenter <error27@gmail.com>
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
---
 drivers/iio/industrialio-backend.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/iio/industrialio-backend.c b/drivers/iio/industrialio-backend.c
index 10e689f49441..cd697fbeae47 100644
--- a/drivers/iio/industrialio-backend.c
+++ b/drivers/iio/industrialio-backend.c
@@ -156,7 +156,7 @@ static ssize_t iio_backend_debugfs_write_reg(struct file *file,
 	ssize_t rc;
 	int ret;
 
-	if (count >= sizeof(buf))
+	if (*ppos != 0 || count >= sizeof(buf))
 		return -ENOSPC;
 
 	rc = simple_write_to_buffer(buf, sizeof(buf) - 1, ppos, userbuf, count);
-- 
2.54.0