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Mon, 10 Aug 2026 08:12:12 -0700 (PDT) Received: from n232-175-066.byted.org ([36.110.163.106]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3925fd95270sm13065069a91.5.2026.08.10.08.12.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 10 Aug 2026 08:12:12 -0700 (PDT) From: guzebing To: tytso@mit.edu Cc: adilger.kernel@dilger.ca, libaokun@linux.alibaba.com, jack@suse.cz, ojaswin@linux.ibm.com, ritesh.list@gmail.com, yi.zhang@huawei.com, djwong@kernel.org, linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org, guzebing Subject: [PATCH] ext4: only update tune mount options when requested Date: Mon, 10 Aug 2026 23:12:00 +0800 Message-Id: <20260810151200.1405562-1-guzebing1612@gmail.com> X-Mailer: git-send-email 2.20.1 Precedence: bulk X-Mailing-List: linux-ext4@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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. Fixes: 04a91570ac67 ("ext4: implemet new ioctls to set and get superblock parameters") Signed-off-by: guzebing --- 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); -- 2.20.1