On Wed, Dec 09, 2020 at 01:15:27AM +0200, Topi Miettinen wrote: > > > > As a further argument, I just did this on a Fedora system: > > > > $ find /dev -perm /ugo+x -a \! -type d -a \! -type l > > > > No results. So making /dev noexec doesn't seem to have any benefit. > > > > > > It's no surprise that there aren't any executables in /dev since > > > removing MAKEDEV ages ago. That's not the issue, which is that > > > /dev is a writable directory (for UID=0 but no capabilities are > > > needed) and thus a potential location for constructing unapproved > > > executables if it is also mounted exec (W^X). > > > > UID 0 can just change mount options, though, unless SELinux or similar is used. And SELinux can protect /dev just fine without noexec. > > Well, mounting would need CAP_SYS_ADMIN in addition to UID 0. Also SELinux > is not universal and the policies might not contain all users or services. > > -Topi What's the data that supports having noexec /dev anyway? With root access I can then just use something else like /dev/shm mount. Has there been out in the wild real world cases that noexec mount of would have prevented? For me this sounds a lot just something that "feels more secure" without any measurable benefit. Can you prove me wrong? /Jarkko
