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Date: Wed, 12 Oct 2022 07:44:30 +1300 From: Paulo Miguel Almeida <paulo.miguel.almeida.rodenas@...il.com> To: David Teigland <teigland@...hat.com> Cc: Kees Cook <keescook@...omium.org>, Christine Caulfield <ccaulfie@...hat.com>, cluster-devel@...hat.com, linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org Subject: Re: [PATCH v2][next] dlm: Replace one-element array with flexible-array member On Tue, Oct 11, 2022 at 10:20:31AM -0500, David Teigland wrote: > On Mon, Oct 10, 2022 at 03:35:24PM -0700, Kees Cook wrote: > > On Mon, Oct 10, 2022 at 04:00:39PM -0500, David Teigland wrote: > > > On Sat, Oct 08, 2022 at 09:03:28PM -0700, Kees Cook wrote: > > > > On Sun, Oct 09, 2022 at 03:05:17PM +1300, Paulo Miguel Almeida wrote: > > > > > On Sat, Oct 08, 2022 at 05:18:35PM -0700, Kees Cook wrote: > > > > > > This is allocating 1 more byte than before, since the struct size didn't change. But this has always allocated too much space, due to the struct padding. For a "no binary changes" patch, the above "+ 1" needs to be left off. > > > > > > > > > > That's true. I agree that leaving "+ 1" would work and produce a > > > > > no-binary-changes patch due to the existing padding that the structure > > > > > has. OTOH, I thought that relying on that space could bite us in the > > > > > future if anyone tweaks the struct again...so my reaction was to ensure > > > > > that the NUL-terminator space was always guaranteed to be there. > > > > > Hence, the change on c693 (objdump above). > > > > > > > > > > What do you think? Should we keep or leave the above > > > > > "+ 1" after the rationale above? > > > > > > > > I think it depends on what's expected from this allocation. Christine or > > > > David, can you speak to this? > > > > > > Hi, thanks for picking through that. Most likely the intention was to > > > allow up to 64 (DLM_LOCKSPACE_LEN) character names, and then use the > > > ls_name[1] for the terminating byte. I'd be happy to take the patch > > > > Should this just use: > > > > char ls_name[DLM_LOCKSPACE_LEN + 1]; > > > > instead, or is the byte savings worth keeping it dynamically sized? > > Yes, I think that's the best option. > Dave > Thanks for the reply Dave; Thanks for the suggestion Kees; I'll send a new patch for it :) Paulo A.
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