These IOCTL commands should be implemented by setting attributes on the superblock, rather than in the IOCTL hooks in struct file_operations. By returning -ENOTTY instead of -ENOIOCTLCMD, we instruct the fs/ioctl.c logic to return -ENOTTY immediately, rather than attempting to call f_op->unlocked_ioctl() or f_op->compat_ioctl() as a fallback. Why this is safe: Before this change, fs/ioctl.c would unsuccessfully attempt calling the IOCTL hooks, and then return -ENOTTY. By returning -ENOTTY directly, we return the same error code immediately, but save ourselves the fallback attempt. Motivation: This simplifies the logic for these IOCTL commands and lets us reason about the side effects of these IOCTLs more easily. It will be possible to permit these IOCTLs under LSM IOCTL policies, without having to worry about them getting dispatched to problematic device drivers (which sometimes do work before looking at the IOCTL command number). Link: https://lore.kernel.org/all/cnwpkeovzbumhprco7q2c2y6zxzmxfpwpwe3tyy6c3gg2szgqd@vfzjaw5v5imr/ Cc: Kent Overstreet <kent.overstreet@xxxxxxxxx> Cc: Christian Brauner <brauner@xxxxxxxxxx> Cc: Jan Kara <jack@xxxxxxx> Cc: Dave Chinner <dchinner@xxxxxxxxxx> Cc: Darrick J. Wong <djwong@xxxxxxxxxx> Cc: Theodore Ts'o <tytso@xxxxxxx> Cc: Josef Bacik <josef@xxxxxxxxxxxxxx> Signed-off-by: Günther Noack <gnoack@xxxxxxxxxx> --- fs/ioctl.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/fs/ioctl.c b/fs/ioctl.c index 1d5abfdf0f22..fb0628e680c4 100644 --- a/fs/ioctl.c +++ b/fs/ioctl.c @@ -769,7 +769,7 @@ static int ioctl_getfsuuid(struct file *file, void __user *argp) struct fsuuid2 u = { .len = sb->s_uuid_len, }; if (!sb->s_uuid_len) - return -ENOIOCTLCMD; + return -ENOTTY; memcpy(&u.uuid[0], &sb->s_uuid, sb->s_uuid_len); @@ -781,7 +781,7 @@ static int ioctl_get_fs_sysfs_path(struct file *file, void __user *argp) struct super_block *sb = file_inode(file)->i_sb; if (!strlen(sb->s_sysfs_name)) - return -ENOIOCTLCMD; + return -ENOTTY; struct fs_sysfs_path u = {}; -- 2.44.0.478.gd926399ef9-goog
