#2732 BLOC Trial-3: JFFS2 does not perserve directory permissions across reboots when using a custom /sbin/init.

[Zarro Boogs per Child]

#2732: JFFS2 does not perserve directory permissions across reboots when using a
custom /sbin/init.
----------------------+-----------------------------------------------------
  Reporter:  mstone   |       Owner:  dwmw2                   
      Type:  defect   |      Status:  assigned                
  Priority:  blocker  |   Milestone:  Trial-3                 
 Component:  distro   |     Version:                          
Resolution:           |    Keywords:  jffs2, updates, security
  Verified:  0        |  
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Comment (by mstone):

 Herbert Pötzl and I spent some time gathering debugging output. We have
 successfully reproduced the bug both on stock 542 images and on custom
 kernels running in QEMU (using your mtdram test device).

 Strace logs of the commands

 {{{
 mkdir a
 chmod 755 a
 }}}

 and

 {{{
 mkdir a
 cp -la a b
 }}}

 reveal that when POSIX ACL support is enabled, 'cp -la' duplicates file
 permissions with a call like:

 {{{
 setxattr("mnt/b", "system.posix_acl_access"...,
 "\x02\x00\x00\x00\x01\x00\x07\x00\xff\xff\xff\xff\x04\x00\x05\x00\xff\xff\xff\xff
 \x00\x05\x00\xff\xff\xff\xff", 28, 0) = 0
 }}}

 whereas mkdir relies on the kernel's implementation of umask support to
 get the correct permissions.

 In both cases, the dentries carry correct permission (0755) but these
 permissions are not propagated to the inodes. (We infer this from the fact
 that the permissions are not preserved across umounts.)

 Disabling POSIX ACLs fixes the problem.

 Note: mkdir() (which relies on the umask and which does not use POSIX ACL
 calls) behaves differently depending on the presence or absence of POSIX
 ACLs.

 We have not yet tested the patch that you included in your previous email.

-- 
Ticket URL: <http://dev.laptop.org/ticket/2732#comment:4>
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