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Unverified Commit 626cbfbb authored by Alessio Balsini's avatar Alessio Balsini Committed by Michael Bestas
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FROMLIST: fuse: 32-bit user space ioctl compat for fuse device 

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.

Bug: 168023149
Link: https://lore.kernel.org/lkml/20210125153057.3623715-3-balsini@android.com/


Signed-off-by: default avatarAlessio Balsini <balsini@android.com>
Change-Id: I595517c54d551be70e83c7fcb4b62397a3615004
Signed-off-by: default avatarAlessio Balsini <balsini@google.com>
parent f8329955

fs/fuse/dev.c

+18 −11
Original line number Diff line number Diff line
@@ -2265,37 +2265,44 @@ 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;



	if (cmd == FUSE_DEV_IOC_CLONE) {

	int res;

	int oldfd;

	struct fuse_dev *fud = NULL;



	if (_IOC_TYPE(cmd) != FUSE_DEV_IOC_MAGIC)

		return -EINVAL;



		err = -EFAULT;

	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.

				 */

				if (old->f_op == file->f_op &&

				    old->f_cred->user_ns == file->f_cred->user_ns)

				    old->f_cred->user_ns ==

					    file->f_cred->user_ns)

					fud = fuse_get_dev(old);



				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 = {

include/uapi/linux/fuse.h

+2 −1
Original line number Diff line number Diff line
@@ -870,7 +870,8 @@ 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;