From 0b509d8d336eef6d622d66b3ae2a1fc3a072bf92 Mon Sep 17 00:00:00 2001 From: Tom Van Braeckel 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 Signed-off-by: Greg Kroah-Hartman --- 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 5bb3a2109ab7..9fd5a91e0d81 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; -- 2.39.5