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    SubjectRe: Security issues with local filesystem caching
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    Ar Mer, 2006-10-25 am 11:14 +0100, ysgrifennodd David Howells:
    > Currently, CacheFiles temporarily changes fsuid and fsgid to 0 whilst doing its
    > own pathwalk through the cache and whilst creating files and directories in the
    > cache. This allows it to deal with DAC security directly. All the directories
    > it creates are given permissions mask 0700 and all files 0000.

    That seems sensible and fine. It is precisely why we added a separate
    fsuid in the first place so that the user space nfsd could take on an fs
    identity without breaking signal and other security based forms.

    > (1) Do all the cache operations in their own thread (sort of like knfsd).

    Slow it down to keep Christoph happy seems iffy

    > (2) Add further security ops for the caching code to call. These might be of
    > use elsewhere in the kernel. These would set cache-specific security
    > labels and check for them.

    I can see good arguments for this in some cases where you want strict
    divisons in extremely secure computing cases but not usually.

    > Thoughts anyone?

    I'd like to know more about why Christoph is objecting, whether he has
    actual real world examples of races/problems it introduces by altering
    fsuid or what his concern is.


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