#12932 NORM Not Tri: fs-save falsely reports success on vfat targets

Zarro Boogs per Child bugtracker at laptop.org
Fri Nov 24 08:38:07 EST 2017

#12932: fs-save falsely reports success on vfat targets
     Reporter:  fatalbert  |                 Owner:  dsd
         Type:  defect     |                Status:  new
     Priority:  normal     |             Milestone:  Not Triaged
    Component:  security   |               Version:  Development firmware
     Keywords:             |            Blocked By:
     Blocking:             |  Deployments affected:
Action Needed:  never set  |              Verified:  0
 Using an xo-4 touch (with 8gb internal storage) and vfat-formatted target
 media (16gb), "fs-save u:\olpc_backup.img" was executed.  In the end it
 reported success.  The "olpc_backup.img" was close to 4gb, which is the
 filesize limit of a vfat filesystem (and half the size of the internal

 Is fs-save using compression?

 If not, then this is a security bug because the user will have a broken
 image and not know that the backup failed until they attempt to do a
 restore (after it's too late to troubleshoot and repeat the backup).

 If fs-save *is* using compression, then there's no security bug here, but
 users need to be informed.  That is, when fs-save reports "success", it
 should print something like "all data compressed to 4gb file named
 olpc_backup.img" for example.  This is important because the user has no
 safe way to verify whether the imaging worked.  Compression or lack
 thereof should also be mentioned in the wiki (which I will do as soon as I
 get a wiki account).

 I believe it's the worst case-- that compression is not used and thus we
 have a security-critical unreported failure.  I say that because I ran
 "strings olpc_backup.img" and there was lots of text that would have been
 compressed if compression were used.

Ticket URL: <http://dev.laptop.org/ticket/12932>
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