fsanitize: member access within null pointer

Scott Kostyshak skostysh at lyx.org
Mon Dec 27 14:48:38 UTC 2021


On Mon, Dec 27, 2021 at 11:32:49AM +0100, Kornel Benko wrote:
> Am Mon, 27 Dec 2021 10:41:49 +0100
> schrieb Pavel Sanda <sanda at lyx.org>:
> 
> > On Sun, Dec 26, 2021 at 09:48:11AM +0100, Kornel Benko wrote:
> > > > I guess clang is not happy with (((struct sockaddr_un *) 0)->sun_path)
> > > > 
> > > > Our own code has:
> > > > #if !defined(SUN_LEN)
> > > > #define SUN_LEN(su) \
> > > >         (sizeof (*(su)) - sizeof ((su)->sun_path) + strlen((su)->sun_path))
> > > > #endif  
> > > 
> > > That was a good guess! With the attached change the message does not appear anymore.  
> > 
> > Apart from that error message is there some functional problem for LyX?
> 
> Not that I am aware of. It manifests only at runtime with sanitize + clang ...

Neither am I.

> > Otherwise I would leave things as they are, it's not our code and sooner
> > or later someone will report this to libc maintainers.
> 
> I think it is unlikely (who else is using sanitize + clang with this code?)

Me, but I'm not planning to report either.

> > (Or it could be
> > you? :)
> 
> :(
> 
> > Or add a comment once we forget...
> 
> Maybe some native English speaker would fit here better.

A comment in LyX's code? Something just like the following?

  // Using Clang and fsanitize suggests there is an issue here but we do
  // not understand the code enough to change it and we are not aware of
  // how to trigger a crash or other issue while using LyX, so we leave
  // it as is. For ML discussion, see here:
  // https://www.mail-archive.com/search?l=mid&q=20211227113249.53bf5a63%40admin1-desktop

Scott
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