lkml.org 
[lkml]   [1999]   [Feb]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    SubjectRe: fsync on large files
    Date
    From

    Linus wrote, re: hardlinked directories:

    > Imagine a
    > chroot() environment, for a moment - symlinks don't work to the outside,
    > but hardlinking does.

    If Linux ever supports hardlinked directories, I really hope there's some way
    to prevent them. That's one of the reasons for the .. sanity check I thought.

    Now:
    * attacker discovers a directory temporarily open (bad permissions)
    * attacker hardlinks to some of the files in there
    * the security checker notices the link count increase

    The future:
    * attacker discovers a directory temporarily open (bad permissions)
    * attacker hardlinks to a subdirectory in it
    * you need yet another security check to check the link count on directories
    matches the number of real files in it, and the check has to watch for
    modifications as it is checking, etc, etc

    It adds a whole new check to Linux security checkers, and a while new
    incompatibility to mainstream Unix.

    Maybe I'm just paranoid. But every little change like this makes me worry.
    (I'm still not happy that ld.so doesn't protect execute-only binaries from
    LD_PRELOADs reading their code pages, and so on... you can't depend on Linux
    enforcing traditional Unix security)

    David.


    -
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.rutgers.edu
    Please read the FAQ at http://www.tux.org/lkml/

    \
     
     \ /
      Last update: 2005-03-22 13:50    [W:0.019 / U:179.888 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site