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fuse: 32-bit user space ioctl compat for fuse device

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With a 64-bit kernel build the FUSE device cannot handle ioctl requests
coming from 32-bit user space.  This is due to the ioctl command
translation that generates different command identifiers that thus cannot
be used for direct comparisons without proper manipulation.

Explicitly extract type and number from the ioctl command to enable 32-bit
user space compatibility on 64-bit kernel builds.

Signed-off-by: Alessio Balsini <balsini@android.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
This commit is contained in:
Alessio Balsini 2021-01-25 15:30:51 +00:00 committed by Miklos Szeredi
parent 3f9b9efd82
commit f8425c9396
2 changed files with 18 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

26
fs/fuse/dev.c
View File

@ -2229,19 +2229,21 @@ static int fuse_device_clone(struct fuse_conn *fc, struct file *new)
static long fuse_dev_ioctl(struct file *file, unsigned int cmd,
unsigned long arg)
{
int err = -ENOTTY;
int res;
int oldfd;
struct fuse_dev *fud = NULL;
if (cmd == FUSE_DEV_IOC_CLONE) {
int oldfd;
if (_IOC_TYPE(cmd) != FUSE_DEV_IOC_MAGIC)
return -ENOTTY;
err = -EFAULT;
if (!get_user(oldfd, (__u32 __user *) arg)) {
switch (_IOC_NR(cmd)) {
case _IOC_NR(FUSE_DEV_IOC_CLONE):
res = -EFAULT;
if (!get_user(oldfd, (__u32 __user *)arg)) {
struct file *old = fget(oldfd);
err = -EINVAL;
res = -EINVAL;
if (old) {
struct fuse_dev *fud = NULL;
/*
* Check against file->f_op because CUSE
* uses the same ioctl handler.
@ -2252,14 +2254,18 @@ static long fuse_dev_ioctl(struct file *file, unsigned int cmd,
if (fud) {
mutex_lock(&fuse_mutex);
err = fuse_device_clone(fud->fc, file);
res = fuse_device_clone(fud->fc, file);
mutex_unlock(&fuse_mutex);
}
fput(old);
}
}
break;
default:
res = -ENOTTY;
break;
}
return err;
return res;
}
const struct file_operations fuse_dev_operations = {

3
include/uapi/linux/fuse.h
View File

@ -903,7 +903,8 @@ struct fuse_notify_retrieve_in {
};
/* Device ioctls: */
#define FUSE_DEV_IOC_CLONE _IOR(229, 0, uint32_t)
#define FUSE_DEV_IOC_MAGIC 229
#define FUSE_DEV_IOC_CLONE _IOR(FUSE_DEV_IOC_MAGIC, 0, uint32_t)
struct fuse_lseek_in {
uint64_t fh;