From mboxrd@z Thu Jan 1 00:00:00 1970 From: =?UTF-8?q?Micka=C3=ABl=20Sala=C3=BCn?= Subject: [PATCH v2 2/5] fs: Add a MAY_EXECMOUNT flag to infer the noexec mount propertie Date: Fri, 6 Sep 2019 17:24:52 +0200 Message-ID: <20190906152455.22757-3-mic@digikod.net> References: <20190906152455.22757-1-mic@digikod.net> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Return-path: List-Post: List-Help: List-Unsubscribe: List-Subscribe: In-Reply-To: <20190906152455.22757-1-mic@digikod.net> To: linux-kernel@vger.kernel.org Cc: =?UTF-8?q?Micka=C3=ABl=20Sala=C3=BCn?= , Aleksa Sarai , Alexei Starovoitov , Al Viro , Andy Lutomirski , Christian Heimes , Daniel Borkmann , Eric Chiang , Florian Weimer , James Morris , Jan Kara , Jann Horn , Jonathan Corbet , Kees Cook , Matthew Garrett , Matthew Wilcox , Michael Kerrisk , =?UTF-8?q?Micka=C3=ABl=20Sala=C3=BCn?= , Mimi Zohar , =?UTF-8?q?Philippe=20Tr=C3=A9buchet?= List-Id: linux-api@vger.kernel.org An LSM doesn't get path information related to an access request to open an inode. This new (internal) MAY_EXECMOUNT flag enables an LSM to check if the underlying mount point of an inode is marked as executable. This is useful to implement a security policy taking advantage of the noexec mount option. This flag is set according to path_noexec(), which checks if a mount point is mounted with MNT_NOEXEC or if the underlying superblock is SB_I_NOEXEC. Signed-off-by: Mickaël Salaün Reviewed-by: Philippe Trébuchet Reviewed-by: Thibaut Sautereau Cc: Al Viro Cc: Kees Cook Cc: Mickaël Salaün --- fs/namei.c | 2 ++ include/linux/fs.h | 2 ++ 2 files changed, 4 insertions(+) diff --git a/fs/namei.c b/fs/namei.c index 209c51a5226c..0a6b9483d0cb 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -2968,6 +2968,8 @@ static int may_open(const struct path *path, int acc_mode, int flag) break; } + /* Pass the mount point executability. */ + acc_mode |= path_noexec(path) ? 0 : MAY_EXECMOUNT; error = inode_permission(inode, MAY_OPEN | acc_mode); if (error) return error; diff --git a/include/linux/fs.h b/include/linux/fs.h index 848f5711bdf0..e57609dac8dd 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -101,6 +101,8 @@ typedef int (dio_iodone_t)(struct kiocb *iocb, loff_t offset, #define MAY_NOT_BLOCK 0x00000080 /* the inode is opened with O_MAYEXEC */ #define MAY_OPENEXEC 0x00000100 +/* the mount point is marked as executable */ +#define MAY_EXECMOUNT 0x00000200 /* * flags in file.f_mode. Note that FMODE_READ and FMODE_WRITE must correspond -- 2.23.0