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author | Tom Van Braeckel <tomvanbraeckel@gmail.com> | 2015-01-12 05:22:16 +0100 |
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committer | Miklos Szeredi <mszeredi@suse.cz> | 2015-03-19 15:29:22 +0100 |
commit | 94e4fe2cab3d43b3ba7c3f721743006a8c9d913a (patch) | |
tree | b6bb327977ae0e4a1173ab32bb4f93f9b460e17e /fs | |
parent | aa991b3b267e24f578bac7b09cc57579b660304b (diff) | |
download | linux-stable-94e4fe2cab3d43b3ba7c3f721743006a8c9d913a.tar.gz linux-stable-94e4fe2cab3d43b3ba7c3f721743006a8c9d913a.tar.bz2 linux-stable-94e4fe2cab3d43b3ba7c3f721743006a8c9d913a.zip |
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>
Diffstat (limited to 'fs')
-rw-r--r-- | fs/fuse/dev.c | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c index 71c4619af333..39706c57ad3c 100644 --- a/fs/fuse/dev.c +++ b/fs/fuse/dev.c @@ -1353,6 +1353,17 @@ static ssize_t fuse_dev_do_read(struct fuse_conn *fc, struct file *file, return err; } +static int fuse_dev_open(struct inode *inode, struct file *file) +{ + /* + * The fuse device's file's private_data is used to hold + * the fuse_conn(ection) when it is mounted, and is used to + * keep track of whether the file has been mounted already. + */ + file->private_data = NULL; + return 0; +} + static ssize_t fuse_dev_read(struct kiocb *iocb, const struct iovec *iov, unsigned long nr_segs, loff_t pos) { @@ -2220,6 +2231,7 @@ static int fuse_dev_fasync(int fd, struct file *file, int on) const struct file_operations fuse_dev_operations = { .owner = THIS_MODULE, + .open = fuse_dev_open, .llseek = no_llseek, .read = do_sync_read, .aio_read = fuse_dev_read, |