From: torvalds@transmeta.com (Linus Torvalds)
To: linux-kernel@vger.kernel.org
Subject: Re: Security question: "Text file busy" overwriting executables but not shared libraries?
Date: Sat, 13 Oct 2001 22:27:30 +0000 (UTC) [thread overview]
Message-ID: <9qaf4i$8qa$1@penguin.transmeta.com> (raw)
In-Reply-To: <20011013205445.A24854@kushida.jlokier.co.uk> <Pine.LNX.4.33.0110131219520.8900-100000@penguin.transmeta.com>
In article <Pine.LNX.4.33.0110131219520.8900-100000@penguin.transmeta.com>,
Linus Torvalds <torvalds@transmeta.com> wrote:
>
>The explicit flag is probably a good idea also because of usage patterns
>(PAGE_COPY is a slowdown _if_ the file is actually written to or even
>mapped shared).
Actually, I missed the obvious case: quite often when you do a "read()",
the reader itself will end up writing to the area read into. In which
case doing the PAGE_COPY would also slow down measurably, due to the
extra overhead of the copy-on-write fault (which not just does the copy
that we tried to avoid, but will take a fault and more VM locks).
So if we want to do this optimization, we _definitely_ want it to be
explicitly controlled by a flag, like O_DIRECT is. There are just too
many cases where it's a pessimization, and while the user can often tell
before-hand, the kernel simply cannot.
Linus
next prev parent reply other threads:[~2001-10-13 22:27 UTC|newest]
Thread overview: 76+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-10-03 12:49 Security question: "Text file busy" overwriting executables but not shared libraries? Jesse Pollard
2001-10-03 18:06 ` Eric W. Biederman
2001-10-03 23:20 ` Rob Landley
2001-10-04 3:38 ` Eric W. Biederman
2001-10-04 4:19 ` Alexander Viro
2001-10-04 6:15 ` Eric W. Biederman
2001-10-04 8:21 ` CaT
2001-10-04 8:35 ` john slee
2001-10-04 8:45 ` CaT
2001-10-04 13:11 ` Eric W. Biederman
2001-10-04 14:24 ` Kernel size Richard B. Johnson
2001-10-13 20:35 ` Aaron Lehmann
2001-10-04 8:30 ` Security question: "Text file busy" overwriting executables but not shared libraries? Ville Herva
2001-10-04 9:46 ` Erik Andersen
2001-10-04 19:50 ` Security question: "Text file busy" overwriting executables but no Kai Henningsen
2001-10-04 8:53 ` Security question: "Text file busy" overwriting executables but not shared libraries? Andreas Schwab
2001-10-04 13:23 ` Eric W. Biederman
2001-10-04 9:12 ` Bloatware (was Re: Security question: "Text file busy"...) VDA
2001-10-04 5:38 ` Security question: "Text file busy" overwriting executables but not shared libraries? Linus Torvalds
2001-10-04 5:44 ` Alexander Viro
2001-10-04 5:49 ` Linus Torvalds
2001-10-04 15:01 ` Eric W. Biederman
2001-10-04 15:49 ` Linus Torvalds
2001-10-04 16:02 ` Richard Gooch
2001-10-04 16:20 ` Andreas Schwab
2001-10-04 17:19 ` Richard Gooch
2001-10-04 16:11 ` Alexander Viro
2001-10-04 19:28 ` Security question: "Text file busy" overwriting executables but no Kai Henningsen
2001-10-04 17:25 ` Security question: "Text file busy" overwriting executables but not shared libraries? Eric W. Biederman
2001-10-13 14:53 ` Jamie Lokier
2001-10-13 17:13 ` Linus Torvalds
2001-10-13 18:18 ` Rik van Riel
2001-10-13 18:40 ` Pablo Alcaraz
2001-10-13 19:05 ` Jamie Lokier
2001-10-13 18:54 ` Jamie Lokier
2001-10-13 19:23 ` Linus Torvalds
2001-10-13 19:46 ` Jamie Lokier
2001-10-13 21:43 ` Aaron Lehmann
2001-10-13 22:27 ` Eric W. Biederman
2001-10-13 22:50 ` Aaron Lehmann
2001-10-15 11:24 ` Jamie Lokier
2001-10-13 22:19 ` Linus Torvalds
2001-10-14 6:49 ` Eric W. Biederman
2001-10-14 8:17 ` Xavier Bestel
2001-10-14 15:40 ` Linus Torvalds
2001-10-14 18:49 ` Eric W. Biederman
2001-10-15 11:43 ` Jamie Lokier
2001-10-13 22:41 ` Richard Gooch
2001-10-15 11:35 ` Jamie Lokier
2001-10-15 11:51 ` Alexander Viro
2001-10-15 12:29 ` Jamie Lokier
2001-10-13 22:27 ` Linus Torvalds [this message]
2001-10-14 12:57 ` Security question: "Text file busy" overwriting executables but no Kai Henningsen
2001-10-14 21:43 ` Security question: "Text file busy" overwriting executables but not shared libraries? Mark H. Wood
2001-10-04 5:53 ` Richard Gooch
2001-10-04 20:39 ` Security question: "Text file busy" overwriting executables but Alan Cox
2001-10-05 16:30 ` Eric W. Biederman
2001-10-05 16:58 ` Linus Torvalds
2001-10-05 17:35 ` Horst von Brand
2001-10-05 17:44 ` Linus Torvalds
2001-10-05 18:51 ` Oliver Xymoron
2001-10-06 19:05 ` Eric W. Biederman
2001-10-14 8:02 ` [RFC] "Text file busy" when overwriting libraries Eric W. Biederman
2001-10-14 12:08 ` Alan Cox
2001-10-14 20:48 ` Eric W. Biederman
2001-10-15 1:44 ` Alan Cox
2001-10-15 2:06 ` Linus Torvalds
2001-10-15 10:11 ` Eric W. Biederman
2001-10-15 11:54 ` Alan Cox
2001-10-15 11:57 ` Alexander Viro
2001-10-15 12:08 ` Alan Cox
2001-10-15 12:11 ` Alexander Viro
2001-10-04 6:50 ` Security question: "Text file busy" overwriting executables but not shared libraries? George Greer
2001-10-04 12:54 ` John Levon
-- strict thread matches above, loose matches on Subject: below --
2001-10-03 2:55 Rob Landley
2001-10-03 7:07 ` Alexander Viro
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