1098112 - Auto-updates broken on Linux when /tmp is mounted noexec

Status: RESOLVED FIXED

(Toolkit :: Application Update, defect)

Description

[François Marier [:francois]]

I've been trying to find out why my Firefox updates weren't working for the last few months (on and off) and finally found the problem: my /tmp is mounted noexec.

If I "mount -o remount,exec /tmp" prior to starting Firefox then it all works fine.

Given that mounting /tmp in a non-executable way is a recommendation from opsec, I hope we can fix this.

I would recommend:

1. detecting this and issuing a warning to point to the cause of the update problems
2. taking advantage of the fact that the installation directory is already executable to run our executables there

#1 is important because I've spent months trying to figure out why I was the only one who's updates were broken.

#2 would be really nice, but I imagine it's not going to be a priority.

Comment 1

[François Marier [:francois]]

Here's the opsec recommendation I was referring to:

  https://mana.mozilla.org/wiki/display/SECURITY/System+Security+Policy+Guidelines+for+Linux+systems#SystemSecurityPolicyGuidelinesforLinuxsystems-Mountsettings

(I don't know why it's locked away in Mana.)

Comment 2

[Robert Strong (they/them - no direct email)]

This is due to the following and other associated code.
http://mxr.mozilla.org/mozilla-central/source/toolkit/xre/nsUpdateDriver.cpp#451

I never liked using tmp so I'll take this.

Comment 3

[Robert Strong (they/them - no direct email)]

Attachment: patch rev1

Pushed to try
https://treeherder.mozilla.org/ui/#/jobs?repo=try&revision=2fa5c125b097

I'm tempted to remove the removal of the MozUpdater-i dirs in temp but would prefer to do that in a separate bug.

Comment 4

[Robert Strong (they/them - no direct email)]

Also tempted to just use the MozUpdater dir and just use Create instead of CreateUnique but I think this is safer since it should protect against file in use issues on Windows.

Comment 5

[Robert Strong (they/them - no direct email)]

try looks good

Comment 6

[Brian R. Bondy [:bbondy]]

Comment on attachment 8529292 [details] [diff] [review]
patch rev1

Review of attachment 8529292 [details] [diff] [review]:
-----------------------------------------------------------------

::: toolkit/mozapps/update/nsUpdateService.js
@@ +1235,5 @@
>      var tmpDir = Cc["@mozilla.org/file/directory_service;1"].
>                   getService(Ci.nsIProperties).
>                   get("TmpD", Ci.nsIFile);
>  
> +    // We used to store MozUpdater-i directories ins the temp directory.

*in the temp directory

Comment 7

[Brian R. Bondy [:bbondy]]

- Addressed nit.

Pushed here:
https://hg.mozilla.org/integration/mozilla-inbound/rev/e57c4cf44a6d

Comment 8

[Carsten Book [:Tomcat]]

https://hg.mozilla.org/mozilla-central/rev/e57c4cf44a6d

Comment 9

[Robert Strong (they/them - no direct email)]

Francois, could you check that this is now fixed in Nightly? Thanks!

Comment 10

[François Marier [:francois]]

I can confirm that it works: I successfully upgraded from 2014-12-07 to 2014-12-08 with a noexec /tmp.

Thanks Robert!