linux/fs/fuse
Tom Van Braeckel 94e4fe2cab fuse: explicitly set /dev/fuse file's private_data
The misc subsystem (which is used for /dev/fuse) initializes private_data to
point to the misc device when a driver has registered a custom open file
operation, and initializes it to NULL when a custom open file operation has
*not* been provided.

This subtle quirk is confusing, to the point where kernel code registers
*empty* file open operations to have private_data point to the misc device
structure. And it leads to bugs, where the addition or removal of a custom open
file operation surprisingly changes the initial contents of a file's
private_data structure.

So to simplify things in the misc subsystem, a patch [1] has been proposed to
*always* set the private_data to point to the misc device, instead of only
doing this when a custom open file operation has been registered.

But before this patch can be applied we need to modify drivers that make the
assumption that a misc device file's private_data is initialized to NULL
because they didn't register a custom open file operation, so they don't rely
on this assumption anymore. FUSE uses private_data to store the fuse_conn and
errors out if this is not initialized to NULL at mount time.

Hence, we now set a file's private_data to NULL explicitly, to be independent
of whatever value the misc subsystem initializes it to by default.

[1] https://lkml.org/lkml/2014/12/4/939

Reported-by: Giedrius Statkevicius <giedriuswork@gmail.com>
Reported-by: Thierry Reding <thierry.reding@gmail.com>
Signed-off-by: Tom Van Braeckel <tomvanbraeckel@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
2015-03-19 15:29:22 +01:00
..
Kconfig fuse: Move CUSE Kconfig entry from fs/Kconfig into fs/fuse/Kconfig 2013-01-17 13:08:45 +01:00
Makefile CUSE: implement CUSE - Character device in Userspace 2009-06-09 11:24:11 +02:00
control.c fuse: add __exit to fuse_ctl_cleanup 2014-04-28 14:19:21 +02:00
cuse.c fuse: flush requests on umount 2014-12-12 09:49:04 +01:00
dev.c fuse: explicitly set /dev/fuse file's private_data 2015-03-19 15:29:22 +01:00
dir.c VFS: (Scripted) Convert S_ISLNK/DIR/REG(dentry->d_inode) to d_is_*(dentry) 2015-02-22 11:38:41 -05:00
file.c Merge branch 'for-3.20/bdi' of git://git.kernel.dk/linux-block 2015-02-12 13:50:21 -08:00
fuse_i.h fuse: add memory barrier to INIT 2015-01-06 10:45:35 +01:00
inode.c fs: remove mapping->backing_dev_info 2015-01-20 14:03:05 -07:00