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    SubjectRe: [PATCH] vfs/eCryptfs: Handle ioctl calls with unlocked and compat functions
    Date
    On Friday 21 May 2010, Tyler Hicks wrote:
    > Lower filesystems that only implement unlocked_ioctl aren't being
    > passed ioctl calls because eCryptfs only checked for
    > lower_file->f_op->ioctl and returned -ENOTTY if it was NULL.
    >
    > eCryptfs shouldn't implement ioctl(), since it doesn't require the BKL.
    > Instead, unlocked_ioctl() should be used and vfs_ioctl() can be called
    > on the lower file since it handles locking, if necessary. This requires
    > vfs_ioctl() to be exported.

    Calling vfs_ioctl doesn't help you at all here, you could simply call
    the ->unlocked_ioctl function of the lower fs directly to do the same,
    because ->ioctl will be gone soon.

    You are howevers still missing a few calls that are done through do_vfs_ioctl
    or file_ioctl. To implement these, you need to add the file and super operations
    that these call and forward the functions to the lower fs.

    > +#ifdef CONFIG_COMPAT
    > +static long
    > +ecryptfs_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
    > +{
    > + long rc = -ENOTTY;
    > + struct file *lower_file = NULL;
    > +
    > + if (ecryptfs_file_to_private(file))
    > + lower_file = ecryptfs_file_to_lower(file);
    > + if (lower_file && lower_file->f_op && lower_file->f_op->compat_ioctl)
    > + rc = lower_file->f_op->compat_ioctl(lower_file, cmd, arg);
    > + return rc;
    > +}
    > +#endif

    You need to return -ENOIOCTLCMD here, not ENOTTY to cover the case where
    the lower file system does not have a ->compat_ioctl function but has its
    calls listed in fs/compat_ioctl.c.

    Arnd


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