Messages in this thread | | | Date | Mon, 10 Oct 2022 15:35:24 -0700 | From | Kees Cook <> | Subject | Re: [PATCH v2][next] dlm: Replace one-element array with flexible-array member |
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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?
-- Kees Cook
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