linux-ext4 - [Bug 203585] Feature Request for filesystems that support noexec/exec mount options

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Date:   Sun, 12 May 2019 17:46:00 +0000
From:   bugzilla-daemon@...zilla.kernel.org
To:     linux-ext4@...r.kernel.org
Subject: [Bug 203585] Feature Request for filesystems that support
 noexec/exec mount options

https://bugzilla.kernel.org/show_bug.cgi?id=203585

Theodore Tso (tytso@....edu) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |tytso@....edu
         Resolution|---                         |WILL_NOT_FIX

--- Comment #1 from Theodore Tso (tytso@....edu) ---
This is not at all trivial to implement, for a number of reasons:

*)  The kernel doesn't have access to the username to uid map.   It might be in
/etc/passwd; but you might also be using LDAP or Yellow Pages for the
username->uid map.   This could done by adding support for this to each file
system which implements this feature request's /sbin/mount.FSTYP, but...

*) This also begs the question of how to handle user namespaces.

The simplest way of solving this problem may be to change the web application
to write its temporary file in some other directory, and let that directory be
writable only by the web application's user id, and let that directory be
mounted without the noexec flag.  If you are using tmpfs, you can mount
multiple tmpfs instances, and create a special one which has mount options just
for that web application, with an fstab entry like this:

tmpfs /run/user/1042 tmpfs
rw,nosuid,nodev,relatime,size=2048k,mode=700,uid=1042,gid=1042 0 0

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