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Sun, 21 Sep 2025 17:25:46 -0700 (PDT) From: Askar Safin To: cyphar@cyphar.com Cc: alx@kernel.org, brauner@kernel.org, dhowells@redhat.com, g.branden.robinson@gmail.com, jack@suse.cz, linux-api@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-man@vger.kernel.org, mtk.manpages@gmail.com, safinaskar@zohomail.com, viro@zeniv.linux.org.uk Subject: Re: [PATCH v4 03/10] man/man2/fspick.2: document "new" mount API Date: Mon, 22 Sep 2025 03:25:29 +0300 Message-ID: <20250922002529.95574-1-safinaskar@gmail.com> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20250919-new-mount-api-v4-3-1261201ab562@cyphar.com> References: <20250919-new-mount-api-v4-3-1261201ab562@cyphar.com> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit > With the notable caveat that in this example, mount(2) will clear all other filesystem parameters (such as MS_NOSUID or MS_NOEXEC); fsconfig(2) will only modify the ro parameter. MS_NOSUID and MS_NOEXEC are not filesystem parameters. They can be set per-mount, but not per-filesystem. Here is list of all filesystem-agnostic per-superblock parameters: https://elixir.bootlin.com/linux/v6.17-rc6/source/fs/namespace.c#L4103 Note that these SB_* constants are equal to corresponding MS_* constants. As you can see, there is no NOSUID and NOEXEC in that list. Also, SB_NOSUID does exist: https://elixir.bootlin.com/linux/v6.17-rc6/source/include/linux/fs.h#L1240 . So, it seems that "NOSUID superblock" does exist as a concept. But, thanks to code in path_mount (provided above) user cannot (in filesystem-agnostic way) make given superblock NOSUID. So, from user point of view, NOSUID and NOEXEC are not filesystem parameters. If you need some example of filesystem parameter, I suggest MS_SYNCHRONOUS, I used it here: https://lore.kernel.org/all/198d1f2e189.11dbac16b2998.3847935512688537521@zohomail.com/ -- Askar Safin