From 0b509d8d336eef6d622d66b3ae2a1fc3a072bf92 Mon Sep 17 00:00:00 2001
From: Tom Van Braeckel <tomvanbraeckel@gmail.com>
Date: Tue, 31 Mar 2015 16:39:21 +0200
Subject: [PATCH] misc: pass miscdevice through file's private_data
Make the miscdevice accessible through the file's private_data.
Previously, this was done only when an open() file operation had been
registered. If no custom open() file operation was defined,
private_data was set to NULL.
This subtle quirk was confusing, to the point where kernel code
registered *empty* file open operations to have private_data point to
the misc device structure and avoid duplicating that logic.
And it could easily lead to bugs, where the addition or removal of a
custom open() file operation surprisingly changes the initial value of
a file's private_data structure.
To resolve this, we now place the miscdevice in the file's private_data
member unconditionally when open() is called.
Signed-off-by: Tom Van Braeckel <tomvanbraeckel@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/char/misc.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)
diff --git a/drivers/char/misc.c b/drivers/char/misc.c
index 5bb3a2109ab72..9fd5a91e0d81e 100644
--- a/drivers/char/misc.c
+++ b/drivers/char/misc.c
@@ -140,12 +140,17 @@ static int misc_open(struct inode * inode, struct file * file)
goto fail;
}
+ /*
+ * Place the miscdevice in the file's
+ * private_data so it can be used by the
+ * file operations, including f_op->open below
+ */
+ file->private_data = c;
+
err = 0;
replace_fops(file, new_fops);
- if (file->f_op->open) {
- file->private_data = c;
+ if (file->f_op->open)
err = file->f_op->open(inode,file);
- }
fail:
mutex_unlock(&misc_mtx);
return err;
--
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