ext4: only update tune mount options when requested

EXT4_IOC_SET_TUNE_SB_PARAM uses set_flags to indicate which superblock
fields the caller wants to update. ext4_sb_setparams() checks set_flags
before updating the other supported fields, but always copied mount_opts
into the on-disk s_mount_opts field.

As a result, callers that do not set EXT4_TUNE_FL_MOUNT_OPTS can still
clear or alter the on-disk default mount options through their unused
mount_opts buffer. This can affect subsequent mounts by changing the
filesystem's stored default mount options.

Only copy mount_opts into s_mount_opts when EXT4_TUNE_FL_MOUNT_OPTS is set,
matching the set_flags semantics used by the other tuneable superblock
fields.

Cc: stable@kernel.org
Fixes: 04a91570ac67 ("ext4: implemet new ioctls to set and get superblock parameters")
Signed-off-by: guzebing <guzebing1612@gmail.com>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Link: https://patch.msgid.link/20260810151200.1405562-1-guzebing1612@gmail.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

0 files changed, 0 insertions, 0 deletions