lkml.org 
[lkml]   [2001]   [May]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: Why side-effects on open(2) are evil. (was Re: [RFD w/info-PATCH]device arguments from lookup)
    Hi!

    > Yes, and that is exactly the difference between having a side effect
    > on the open(2), versus having the effect as a result of a write(2).
    >
    > Unfortunately, there are already some cases where an open
    > on a device can have unexpected results. If you don't want
    > to get blocked waiting for the carrier-detect signal from the
    > modem when opening a tty device, you had better specify the
    > O_NONBLOCK option on the open. If you don't want this flag
    > to be active during the actual I/O operations, then you would
    > have to do an fcntl to clear the O_NONBLOCK again after the open.
    >
    > So I guess things have already been a bit messy in this
    > area for many years, even before linux even existed, and
    > in some cases you can't really do anything about it because
    > the behaviour is mandated by the applicable standards, like
    > POSIX, SUS, or whatever.
    > (The blocking of the open on a tty device is explicitly
    > documented in my copy of the X/Open specification.)
    >
    > Fortunately, blocking the nightly backup program by making it
    > accidentally open a tty is not quite as catastrophic as having
    > it start a nuclear war, or format the disks, or something,
    > just because a user was playing games with symlinks.

    Maybe not *as* catastrophic, but security hole, anyway. User should
    not be able to block system backups.

    Small demonstration for bugtraq, anyone?
    Pavel
    --
    I'm pavel@ucw.cz. "In my country we have almost anarchy and I don't care."
    Panos Katsaloulis describing me w.r.t. patents at discuss@linmodems.org
    -
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

    \
     
     \ /
      Last update: 2005-03-22 12:53    [W:0.025 / U:0.024 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site