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Message-ID: <20110724132913.GH27634@port70.net>
Date: Sun, 24 Jul 2011 15:29:14 +0200
From: Szabolcs Nagy <nsz@...t70.net>
To: musl@...ts.openwall.com
Subject: Re: holywar: malloc() vs. OOM
* Rich Felker <dalias@...ifal.cx> [2011-07-24 08:40:34 -0400]:
> On Sun, Jul 24, 2011 at 02:33:25PM +0400, Vasiliy Kulikov wrote:
> > But looking at the problem from the pragmatic point of view we'll see
> > that libc is actually the easiest place where the problem may be
> > workarounded (not fixed, surely). The workaround would be simply
> > raising SIGKILL if malloc() fails (either because of brk() or mmap()).
> > For the rare programs craving to handle OOM such code should be used:
>
> This is absolutely wrong and non-conformant. It will also ruin all
> A better solution might be to have a gcc option to generate a read
> from the base address the first time a function performs arithmetic on
> a pointer it has not already checked. This is valid because the C
sounds reasonable
> > Probably I overestimate the importance of OOM errors, and (1) in
> > particular. However, I think it is worth discussing.
>
> I don't think you overestimate the importance of OOM errors. Actually
> Linux desktop is full of OOM errors that ruin usability, like file
> managers that hang the system for 5 minutes then crash if you navigate
> to a directory with a 15000x15000 image file. Unfortunately I don't
> think it's possible to fix at the libc level, and fixing the worst
> issues (DoS from apps crashing when they should not crash) usually
> involves both sanity-checking the size prior to calling malloc *and*
> checking the return value of malloc...
what about providing an alternative libc or libcwrapper api
it could "fix" deprecated/dangerous calls
(maybe turn them into compiletime errors)
and things like oom failures into runtime errors
so bad code can be compiled against this radical extremist libc
i guess for now running code under valgrind can catch most
of these issues..
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