Re: [PATCH] xfsdump: avoid false-positive __strcpy_chk abort on long dirent names

[Christoph Hellwig <hch@infradead.org>]

On Fri, Jun 26, 2026 at 12:28:27AM +0000, vmfunc wrote:
> On Thu, Jun 25, 2026 at 03:57:58PM -0700, Darrick J. Wong wrote:
> > Why wouldn't you fix the structure definitions to use the proper VLA
> > syntax (dh_name[]) instead of making the code less readable?
> 
> looked at that first but dh_name[] doesnt drop in cleanly here. the
> declared size isnt slack padding, its the count of name bytes carried
> inline in the fixed-size on-media header, n read_dirent() in
> restore/content.c reads the record back out using sizeof() of that member:
> 
> 	namep = dhdrp->dh_name + sizeof(dhdrp->dh_name);
> 	memcpy(dhdrp->dh_name, dhdr_v1.dh_name, sizeof(dhdr_v1.dh_name));

To me it looks like the problem is that mix up the on-disk and
in-memory structure with different semantics here.  The somewhat
more invasive fix would be to split the

direnthdr structure into an in-memory direnthdr one, and an on-disk
direnthdr_v3.  The former would use a VLA, and the latter the existing
hard coded value.  This would also allow to make the endian conversion
in xlate_direnthdr/xlate_direnthdr_v1 type safe.