7.3-stable review patch. If anyone has any objections, please let me know. ------------------ From: guzebing [ Upstream commit 981eec6c300bd4e84ffac8f3c28b762d00f13e9c ] 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 Reviewed-by: "Darrick J. Wong" Link: https://patch.msgid.link/20260810151200.1405562-1-guzebing1612@gmail.com Signed-off-by: Theodore Ts'o Signed-off-by: Sasha Levin --- fs/ext4/ioctl.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c index c8387e6a2c6e9..1f6d7afb62ec7 100644 --- a/fs/ext4/ioctl.c +++ b/fs/ext4/ioctl.c @@ -1362,7 +1362,8 @@ static void ext4_sb_setparams(struct ext4_sb_info *sbi, es->s_encoding = cpu_to_le16(params->encoding); if (params->set_flags & EXT4_TUNE_FL_ENCODING_FLAGS) es->s_encoding_flags = cpu_to_le16(params->encoding_flags); - strscpy_pad(es->s_mount_opts, params->mount_opts); + if (params->set_flags & EXT4_TUNE_FL_MOUNT_OPTS) + strscpy_pad(es->s_mount_opts, params->mount_opts); if (params->set_flags & EXT4_TUNE_FL_EDIT_FEATURES) { es->s_feature_compat |= cpu_to_le32(params->set_feature_compat_mask); -- 2.53.0