linux-kernel - Re: [PATCH 1/2] ipc, msg: fix message length check for negative values

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Message-ID: <CA+55aFxeGaZjWM37e4p1tAhjwocpv0_iU0jTYUfaAFagvCBxmQ@mail.gmail.com>
Date:	Sat, 2 Nov 2013 17:35:12 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Mathias Krause <minipli@...glemail.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Davidlohr Bueso <davidlohr@...com>,
	Pax Team <pageexec@...email.hu>,
	Brad Spengler <spender@...ecurity.net>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] ipc, msg: fix message length check for negative values

On Sat, Nov 2, 2013 at 2:26 PM, Mathias Krause <minipli@...glemail.com> wrote:
> On 64 bit systems the test for negative message sizes is bogus as the
> size, which may be positive when evaluated as a long, will get truncated
> to an int when passed to load_msg().

Quite frankly, wouldn't it be much nicer to just fix "load_msg()" instead?

Using "size_t" also gets rid of the games we play with DATALEN_MSG/SEG.

IOW, something like the attached..

Of course, we *also* should fix ns->msg_ctlmax to make clear you can't
use negative numbers there. No question about that. I think it would
be better to even avoid INT_MAX, because there are memory use concerns
and CPU usage ones too (we generate that list of
smaller-than-page-size fragments).

Hmm?

              Linus

View attachment "patch.diff" of type "text/x-patch" (2585 bytes)