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authorEric W. Biederman <ebiederm@xmission.com>2016-06-10 12:21:40 -0500
committerEric W. Biederman <ebiederm@xmission.com>2016-06-15 06:52:23 -0500
commit695e9df010e40f407f4830dc11d53dce957710ba (patch)
tree9f945a72c428a3fdfb66d999fed31d0b7374f12c /Documentation
parentd71ed6c930ac7d8f88f3cef6624a7e826392d61f (diff)
mnt: Account for MS_RDONLY in fs_fully_visible
In rare cases it is possible for s_flags & MS_RDONLY to be set but MNT_READONLY to be clear. This starting combination can cause fs_fully_visible to fail to ensure that the new mount is readonly. Therefore force MNT_LOCK_READONLY in the new mount if MS_RDONLY is set on the source filesystem of the mount. In general both MS_RDONLY and MNT_READONLY are set at the same for mounts so I don't expect any programs to care. Nor do I expect MS_RDONLY to be set on proc or sysfs in the initial user namespace, which further decreases the likelyhood of problems. Which means this change should only affect system configurations by paranoid sysadmins who should welcome the additional protection as it keeps people from wriggling out of their policies. Cc: stable@vger.kernel.org Fixes: 8c6cf9cc829f ("mnt: Modify fs_fully_visible to deal with locked ro nodev and atime") Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
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