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    SubjectRe: RFC: BSD system call revoke?
    On Thu, 24 Jun 1999 hagopiar@vuser.vu.union.edu wrote:
    >
    > Should a user be able to revoke a file descriptor opened by a root
    > processes in the first place?
    > -Rob H.

    Ok, good question. Let's look at the permisstion issue:

    I had this check in my revoke attempt:

    + retval = -EPERM;
    + if (!capable(CAP_DAC_OVERRIDE &&
    + current->fsuid != dentry->d_inode->i_uid)) {
    + goto out_dput;
    + }

    I agree that revoke should be limited to block and char devices, this way
    users that don't get ownership of a block/char device cannot do anything
    bad with it.

    Processes with capability CAP_DAC_OVERRIDE can open any file, so i think
    CAP_DAC_OVERRIDE processes which get an EOF because of an user revoked his
    block/char device, should be prepared to reopen it, so I see no need to
    use a different revoke behavor in linux compared to BSD. It's there and
    it would have been changed if there were any problem with it.

    Comments?

    - Bernd

    >
    > On Wed, 23 Jun 1999, Chris Evans wrote:
    >
    > > 2) The impact of allowing arbitrary users to call revoke() on files they
    > > own is unassessed, making it very very dangerous. root-owned processes
    > > often deal with users' files, and may not be prepared to deal with a file
    > > descriptor disappearing from under them. Hence I suggest limiting this
    > > call to block devices/char devices.
    >
    >



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