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Open Source and information security mailing list archives
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Date: Fri, 30 Mar 2007 15:56:35 +0100 From: Alan Cox <alan@...rguk.ukuu.org.uk> To: "Aubrey Li" <aubreylee@...il.com> Cc: "David Howells" <dhowells@...hat.com>, vapier.adi@...il.com, jie.zhang@...log.com, bryan.wu@...log.com, "Andrew Morton" <akpm@...ux-foundation.org>, linux-kernel@...r.kernel.org Subject: Re: [PATCH] nommu arch dont zero the anonymous mapping by adding UNINITIALIZE flag > I can't find mmap must give zeroed memory in the mmap manual. > Is there any reason relying on anon mmap() giving zerod memory? Its how all Unix/Linux like systems behave. You have to clear the memory to something to deal with security on any kind of real system, and zero is a good a value as any > > Personally, I'd prefer to maintain compatibility with MMU-mode wherever > > possible, but I'm happy with overrides like the MAP_UNINITIALISED flag > > suggested. > > > Not necessary IMHO. mmap() for anonymous memory pools should not normally be a hot path, because the C library malloc is supposed to show some brains. If you need special behaviour (eg for performance hacks) then create yourself a /dev/zero like device which just maps uncleared pages. Its not much code and it keeps special cases out of the core kernel. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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